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Exercise training increases telomerase reverse transcriptase gene expression
and telomerase activity: A systematic review and meta-analysis
Article  in  Ageing Research Reviews · July 2021
DOI: 10.1016/j.arr.2021.101411
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University of Southern Queensland 
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Qatar University
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Total document: 10655 
 Main text: 5732 
Abstract: 248 
Number of tables: 2 
Number of figures: 6 
Number of references: 62 
Supplementary files: 3 
 
Exercise training increases telomerase reverse transcriptase gene expression and telomerase activity: A 
systematic review and meta-analysis 
 
Running title: Exercise, TERT and telomerase 
 
Joshua Denham1,* & Maha Sellami2 
1 RMIT University, School of Health and Biomedical Sciences, Melbourne, Victoria, Australia 
2 Qatar University, College of Education, Physical Education Department, Doha, Qatar 
 
 
 
*Corresponding Author: Room 53, Level 4, Building 202, School of Health and Biomedical Sciences, 
Bundoora West Campus, RMIT University, Bundoora, VIC 3083; Ph: +613 9925 6525; email: 
josh.denham@rmit.edu.au 
 
Keywords: Telomere, biological ageing, senescence, TERT 
 2 
Highlights 
• Physical activity, endurance exercise and maximal aerobic fitness is associated with telomere 
length maintenance, yet the molecular mechanisms remain unclear. 
• Both a single bout of exercise and long-term exercise training increase TERT/telomerase 
activity. 
• Endurance athletes exhibited increased leukocyte TERT/telomerase activity compared to 
inactive controls. 
• Exercise training could preserve telomeres through telomerase upregulation to support 
healthy biological ageing. 
 
 3 
Abstract 
Telomeres protect genomic stability and shortening is one of the hallmarks of ageing. Telomerase 
reverse transcriptase (TERT) is the major protein component of telomerase, which elongates 
telomeres. Given that short telomeres are linked to a host of chronic diseases and the therapeutic 
potential of telomerase-based therapies as treatments and a strategy to extend lifespan, lifestyle 
factors that increase TERT gene expression and telomerase activity could attenuate telomere 
attrition and contribute to healthy biological ageing. 
Physical activity and maximal aerobic fitness are associated with telomere maintenance, yet the 
molecular mechanisms remain unclear. Therefore, the purpose of this systematic review and meta-
analysis was to identify the influence of a single bout of exercise and long-term exercise training on 
TERT expression and telomerase activity. A search of human and rodent trials using the PubMed, 
Scopus, Science Direct and Embase databases was performed. 
Based on findings from the identified and eligible trials, both a single bout of exercise (n; 
standardised mean difference [95%CI]: 5; SMD: 1.19 [0.41–1.97], p=0.003) and long-term exercise 
training (10; 0.31 [0.03–0.60], p=0.03) up-regulates TERT and telomerase activity in non-cancerous 
somatic cells. As human and rodent studies were included in the meta-analyses both exhibited 
heterogeneity (I2=55–87%, p<0.05). Endurance athletes also exhibited increased leukocyte TERT and 
telomerase activity compared to their inactive counterparts. These findings suggest exercise training 
as an inexpensive lifestyle factor that increases TERT expression and telomerase activity. Regular 
exercise training could attenuate telomere attrition through a telomerase-dependent mechanism 
and ultimately extend health-span and longevity. 
 
 
 
 
 
 
 
 
 
 
 
 
 
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1.0 Introduction 
Ageing is a complex process that progressively impairs tissue function. Ageing is reflected by the 
slow degradation of an evolutionary conserved, repetitive, terminal DNA located at the 
chromosomal ends, namely telomeres. Telomeres and six interacting – shelterin – proteins ensure 
genomic stability (Sfeir and de Lange, 2012). Telomere attrition is one of the key hallmarks of ageing, 
as significant telomere shortening occurs across the lifespan (Lopez-Otin et al., 2013) and telomere-
based therapies extends both life and health span in rodents (Martinez and Blasco, 2017). 
Without adequate telomerase activity, somatic cell telomeres progressively shorten with each round 
of division owing to the end replication problem (Levy et al., 1992). Telomere attrition culminates in 
replicative senescence once a critical length is reached. Thus, telomere length represents cellular 
replicative capacity. Critically short telomeres causes telomere dysfunction that can also trigger cell 
apoptosis (Deng et al., 2008; Rajaramanet al., 2007). In turn, replicative senescence contributes to 
tissue biological ageing and is associated with an increased risk of age-related diseases (e.g. coronary 
artery disease, type 2 diabetes, Alzheimer’s disease) (D'Mello et al., 2015; Forero et al., 2016; 
Haycock et al., 2014). Telomeres are, however, maintained through alternative lengthening of 
telomeres (ALT) and the reverse transcriptase enzyme, telomerase (Zhang and Zou, 2020). The 
former is typically identified in a minority of cancers (Cesare and Reddel, 2010; Zhang and Zou, 
2020), whereas telomerase activity is high in most tissues in small animals and generally at very low 
levels in large mammals, including humans (Seluanov et al., 2007; Tian et al., 2018). 
Telomerase reverse transcriptase (TERT) is the major protein and catalytic, rate-limiting component 
of telomerase. Importantly, TERT gene expression is highly correlated with telomerase activity in 
somatic cells (Gizard et al., 2011; Saretzki et al., 2002; Wang et al., 2014). TERT-based – gene – 
therapies have attracted considerable attention in recent years given the findings emphasising that 
telomerase extends the lifespan of cultured cells enabling their continued proliferation (Counter et 
al., 1998; Zhu et al., 1999). The life and health spans of mice are also extended without increasing 
the risk of neoplasms after receiving TERT gene therapy (Bernardes de Jesus et al., 2012). Targeted 
AAV9-Tert therapy can also treat diseases associated with, what is usually, irreparable tissue 
damage. For instance, pulmonary fibrosis and myocardial infarction-induced cardiac necrosis are 
significantly reduced after AAV9-Tert therapy and are associated with improvements in organ 
function and survivability (Bar et al., 2014; Povedano et al., 2018). 
While human trials involving TERT-based gene therapies have begun, other non-invasive strategies 
for telomere length maintenance should be considered. Both human and rodent studies have 
implicated physical exercise training as a lifestyle factor associated with telomere maintenance 
 5 
(Arsenis et al., 2017; Denham et al., 2016a). Two meta-analyses have supported the premise that 
active individuals, on average, possess longer somatic cell telomeres compared to their inactive 
peers (Lin et al., 2019; Mundstock et al., 2015), yet the underlying mechanisms remain incompletely 
understood. Furthermore, endurance athletes who regularly engage in strenuous aerobic training, 
on average, possess longer leukocyte telomeres compared to their inactive counterparts and 
increased abundance of TERT expression and telomerase activity (Denham et al., 2013; Denham et 
al., 2016b; Hagman et al., 2020; Werner et al., 2009). Given the critical role of telomerase in 
telomere maintenance, the utility of TERT gene therapy to combat premature biological ageing and 
in the treatment of age-related diseases, the purpose of this systematic review and meta-analysis 
was to establish the influence of exercise on TERT gene expression and telomerase activity in healthy 
somatic cells from mammals. 
 
2.0 Materials and Methods 
2.1 Protocol 
This systematic review and meta-analysis was conducted according to the Preferred Reporting Items 
for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. It was conducted according to the 
Australian code for the care and use of animals for scientific purposes (the Code) from the National 
Health and Medical Research Council of Australia (NHMRC). The search strategy was designed to 
answer the following research question: “Does a single bout of exercise or chronic exercise training 
increase either telomerase activity, TERT mRNA or protein expression in non-cancerous somatic 
cells?” 
2.2 Search strategy 
A comprehensive search of the PubMed (National Library of Medicine), Embase, Scopus and Elsevier 
ScienceDirect databases was performed by JD in September 2020 using search terms outlined in 
Supplementary Table 1. The PubMed database was also searched with the search terms as well as 
the ‘exercise’ MESH term. The Elsevier ScienceDirect search was restricted to title, abstract and 
author specified keywords, as well as ‘research articles’ and ‘short communications’. The Embase 
search was restricted to terms in the title and abstract and ‘article’ as a type of publication, and the 
Scopus search was restricted to title and abstract and journals (sources). The PubMed and Scopus 
searches were restricted to manuscripts written in English. The bibliographies of the screened 
journal articles that were read in full were reviewed for eligible papers and one additional 
manuscript was identified. Conference proceedings, abstracts and published work that was not peer 
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reviewed were not included in this review. All references were exported from the search databases 
and managed in EndNote (X9.3.3). 
2.3 Types of studies (inclusion/exclusion criteria) 
The study synthesis and meta-analysis was restricted to published, peer-reviewed journal articles 
written in English. The inclusion criteria was as follows: 1) an exercise (single bout or chronic 
training) intervention; 2) An analysis of telomerase activity/TERT mRNA or TERT protein content 
from non-cancerous tissue; 3) studies involving mammals. It was important to restrict our synthesis 
and meta-analysis to studies that included the analysis of non-cancerous tissues and mammals, as 
some cancers exhibit elevated telomerase activity that promotes their survival and mammals share a 
common telomere sequence (5’-TTAGGG-3’), comparable telomere biology (e.g. shelterin proteins 
and telomerase) and telomere regulating mechanisms. Studies involving in vitro experiments 
designed to analyse the effect of exercise on telomerase, TERT mRNA or protein abundance, cross-
sectional and association studies (except for rodent studies when euthanasia was necessary for 
tissue collection), review articles or cohort studies were excluded. Moreover, any interventions that 
did not examine exercise as the main lifestyle intervention or involved multiple lifestyle changes 
(e.g. meditation, counselling and/or diet) were excluded, since any potential effects of exercise on 
the telomerase/TERT could not be explained by exercise training alone. Finally, conference 
proceedings, book chapters and editorials were also excluded as data were likely not peer-reviewed 
and practical issues with assessing their risk of bias. If the inclusion of a study was uncertain based 
on the initial screening of the title and abstract, the full-text was retrieved (second screening) and 
read before a decision was made. The Prisma flow diagram is displayed in Figure 1. 
2.4 Data extraction 
Data extraction was performed by JD. Data extraction included authors (date), journal, title of the 
work, year of publication, Participant/animal characteristics (participant/animal, N in the exercise 
group, sex, training status and VO2max), tissue type, analysis (e.g. TERT mRNA, protein and/or 
telomerase activity), analysis method and exercise trial details. To be included in the meta-analysis, 
study data must have presented the mean ± standard deviation or standard error from the mean 
from each group (rodents) or time-point (human exercise trials) of either the TERT mRNA, protein or 
telomerase activity. When this information was missing from the manuscript and online 
supplementary material, one of the named researchers on the manuscript was contacted and a 
request for the data was made via email in late September 2020. Another request was sent via email 
in October and again in November 2020. Data were excluded from the meta-analysis for the 
 7 
following reasons: 1) author indicated they no longer had the data; 2) author did not respond to our 
emails; or 3) the author declined our request for the necessary data (summarised in Supplementary 
Table 2). However, the manuscripts excluded from the meta-analysisremained in the systematic 
review. A number of studies also examined the differences in leukocyte TERT or PBMC telomerase 
activity between human endurance athletes and healthy controls (summarised in Supplementary 
Table 3). These studies were summarised in a separate analysis. 
2.5 Quality assessment 
The Cochrane Risk of Bias Tool was used to assess the bias of studies included in the systematic 
review. The Cochrane Risk of Bias Tool assesses multiple sources of study bias: selection bias, 
reporting bias, other sources of bias, performance bias, detection bias and attrition bias. Bias in each 
domain is classified as high, unclear or low, and scored 3, 2 or 1, respectively. An aggregate score 
was calculated to establish the overall risk of bias of all included studies to determine the overall 
quality of the literature. The risk of bias was calculated independently by both authors (JD and MS). 
Any discrepancies in risk of bias scores were resolved by discussion until agreement. 
2.6 Data analysis and presentation 
Data were organised using electronic spreadsheet programming (Microsoft Excel). Data analyses 
were performed by JD. Relative expression/abundance/activity (expressed in arbitrary units [AU], 
mean ± SD) between the basal telomerase activity, TERT mRNA or TERT protein expression and the 
post-exercise time-point (human trials) were analysed. For the rodent studies the relative 
expression/abundance/activity (AU, mean ± SD) in telomerase activity, TERT mRNA or TERT protein 
expression from exercised rodents were compared to controls (no exercise) in analyses. For the 
acute exercise analyses, telomerase activity recorded at baseline compared to immediately after 
exercise training was used in analyses, whilst TERT mRNA analysis was restricted to baseline 
compared to 1 hr post training. Effect sizes of the influence of exercise (short and long-term training) 
on telomerase activity or TERT mRNA/protein expression were calculated from each comparison 
with random effect meta-analyses using Review Manager (version 5.4). Effect size confidence 
intervals were calculated using the random-effects method with an α = 0.05. Publication bias was 
visually assessed by plotting the effect sizes against the standard error using funnel plots. The fold-
difference (FD) of leukocyte TERT gene expression or PBMC telomerase activity between endurance 
athletes compared to healthy controls were presented in a bar graph. Graphs were developed using 
GraphPad Prism (version 9.0.0). 
 
 8 
3.0 Results 
3.1 Search strategy 
Figure 1 outlines the search strategy and screening process. The search strategy identified 1700 
articles and another one was identified after reviewing the bibliography of eligible manuscripts. Of 
those articles, 1170 were duplicates and subsequently removed. The title and abstract of the 
remaining 530 articles were read to assess their eligibility for inclusion and 489 were removed. Full-
texts of the remaining 41 articles were retrieved and read in full, and a further 17 were excluded 
from the qualitative synthesis for reasons outlined in Figure 1. Twenty-four articles were included in 
the qualitative synthesis. Fifteen were included in the meta-analysis, as the necessary data required 
for the analyses were not reported in the full-text of some articles and were not available upon 
request (Supplementary Table 2). 
 
3.2 Study characteristics 
A summary of the human and rodent studies included in the systematic review are outlined in Table 
1 and 2, respectively. Studies were published between 2001 and 2020. The first study was published 
in 2001 (Radak et al., 2001), one study was published in 2008 (Werner et al., 2008), 2009 (Werner et 
al., 2009) and 2011 (Wolf et al., 2011), three in 2012 (Ho et al., 2012; Laye et al., 2012; Ludlow et al., 
2012), one in 2014 (Chilton et al., 2014), three in 2016 (Duan et al., 2016; Mychasiuk et al., 2016; 
Saki et al., 2016) and 2017 (Cluckey et al., 2017; Ludlow et al., 2017; Zietzer et al., 2017), four in 2018 
(Booth et al., 2018; de Carvalho Cunha et al., 2018; Noorimofrad and Ebrahim, 2018; Puterman et 
al., 2018), three in 2019 (Cheung et al., 2019; Saghebjoo et al., 2019; Werner et al., 2019) and three 
in 2020 (Nickels et al., 2020; Sadeghi-Tabas et al., 2020; Vita et al., 2020). 
3.2.1 Human trials 
Twelve studies involving 16 experimental trials were published. Human studies analysed TERT 
expression or telomerase activity after a single bout of exercise (Chilton et al., 2014; Cluckey et al., 
2017; Zietzer et al., 2017), chronic exercise training (Cheung et al., 2019; Duan et al., 2016; Ho et al., 
2012; Laye et al., 2012; Nickels et al., 2020; Noorimofrad and Ebrahim, 2018; Puterman et al., 2018; 
Saki et al., 2016) or both (Werner et al., 2019). Participants were healthy individuals (Chilton et al., 
2014; Duan et al., 2016; Nickels et al., 2020; Noorimofrad and Ebrahim, 2018; Werner et al., 2019), 
domestic abuse survivors (Cheung et al., 2019), ultra-marathon runners (Laye et al., 2012), family 
caregivers (Puterman et al., 2018), cardiac outpatients (Saki et al., 2016), or chronic fatigue patients 
(Ho et al., 2012). Although not all studies specifically stated the ethnicities of participants, there 
appeared to be a range of ethnic groups with participants from the UK (Nickels et al., 2020), USA 
(Cluckey et al., 2017), Australia (Chilton et al., 2014) and European countries [Germany (Werner et 
 9 
al., 2019; Zietzer et al., 2017) and Denmark (Laye et al., 2012)], Chinese (Cheung et al., 2019; Duan et 
al., 2016; Ho et al., 2012) and Middle Eastern (Iran (Noorimofrad and Ebrahim, 2018; Saki et al., 
2016)), based on the author affiliations and experimental methods sections. One study included a 
mixed ethnic group (white, Asian and black individuals) from the USA (Puterman et al., 2018). While 
a total of 82 (30 women) were involved in the single exercise session trials ranging from an n of 15 
(Werner et al., 2019) to 26 (Zietzer et al., 2017), 386 (291 women) individuals were involved in the 
chronic exercise training studies ranging from an N of 9 (Laye et al., 2012) to 136 (Cheung et al., 
2019) (Table 1). The average age of participants ranged from 19.5 ± 1.1 years (Noorimofrad and 
Ebrahim, 2018) to 59.58 ± 5.56 years old (Duan et al., 2016) (Table 1). One study analysed whole 
blood leukocytes (Nickels et al., 2020), another analysed whole blood leukocytes as well as sorted t-
cells (CD4+CD45RO+ and CD8+CD45RA+) (Chilton et al., 2014), 9 analysed PBMCs (Cheung et al., 
2019; Cluckey et al., 2017; Duan et al., 2016; Ho et al., 2012; Laye et al., 2012; Noorimofrad and 
Ebrahim, 2018; Puterman et al., 2018; Saki et al., 2016; Zietzer et al., 2017) and another study 
analysed PBMCs, CD14+ and CD34+ leukocytes (Werner et al., 2019). Of the human studies, 
resistance training (with an emphasis on muscular endurance, which would stress the aerobic energy 
system) (Nickels et al., 2020), aerobic training (Chilton et al., 2014; Cluckey et al., 2017; Laye et al., 
2012; Noorimofrad and Ebrahim, 2018; Puterman et al., 2018; Zietzer et al., 2017), both types of 
training (aerobic and resistance) (Saki et al., 2016; Werner et al., 2019), Tai Chi (Duan et al., 2016) 
and Qigong (Cheung et al., 2019; Ho et al., 2012) exercise interventions were implemented. 
The studies that examined the effects of a single bout of exercise were 30- (Chilton et al., 2014; 
Cluckey et al., 2017), 35- (Zietzer et al., 2017) or 45-min sessions (Werner et al., 2019) at low to 
moderate (Zietzer et al., 2017) or high intensities (Chilton et al., 2014; Cluckey et al., 2017; Werner 
et al., 2019). Post exercise samples after a single bout of exercise ranged from immediately after the 
cessation of exercise (Chilton et al., 2014; Werner et al., 2019), 10 min after (Zietzer et al., 2017), 30 
min (Cluckey et al., 2017), 60 min (Chilton et al., 2014;Cluckey et al., 2017), 90 min after (Cluckey et 
al., 2017) and 24 hours after (Werner et al., 2019) exercise. Of these studies, one analysed PBMC 
telomerase activity (Zietzer et al., 2017), another analysed telomerase activity in PBMCs and sorted 
leukocytes (CD14+ and CD34+) (Werner et al., 2019) and one analysed TERT mRNA in whole blood 
leukocytes and leukocyte subsets (CD4+CD45RO+ T cell and CD8+CD45RA+ T cell) (Chilton et al., 
2014). 
The duration of exercise training interventions were one (Laye et al., 2012), nine (Noorimofrad and 
Ebrahim, 2018), 12 (Nickels et al., 2020), 16 (Ho et al., 2012), 22 (Cheung et al., 2019), 24 weeks 
(Duan et al., 2016; Puterman et al., 2018; Werner et al., 2019). Training was performed two (Cheung 
 10 
et al., 2019; Ho et al., 2012; Nickels et al., 2020), three (Noorimofrad and Ebrahim, 2018; Saki et al., 
2016; Werner et al., 2019), 3–5 (Puterman et al., 2018), five (Duan et al., 2016) or seven (Laye et al., 
2012) times per week at relatively low (Cheung et al., 2019; Duan et al., 2016), moderate (Laye et al., 
2012; Puterman et al., 2018; Saki et al., 2016; Werner et al., 2019) or high intensities (Nickels et al., 
2020; Noorimofrad and Ebrahim, 2018; Werner et al., 2019). One study analysed TERT mRNA in 
whole blood (Nickels et al., 2020), one analysed skeletal muscle and PBMC TERT mRNA and 
telomerase activity (Laye et al., 2012) and seven analysed PBMC telomerase activity (Cheung et al., 
2019; Duan et al., 2016; Ho et al., 2012; Noorimofrad and Ebrahim, 2018; Puterman et al., 2018; Saki 
et al., 2016; Werner et al., 2019) (Table 1). Notably, TERT expression nor telomerase activity were 
detected in human skeletal muscle before or after exercise (Laye et al., 2012). 
 
3.2.2 Rodent experiments 
Twelve studies involving rodents were identified (Table 2). Tert mRNA, protein or telomerase activity 
were investigated in skeletal muscle (tibialis anterior or gastrocnemius) (de Carvalho Cunha et al., 
2018; Ludlow et al., 2012; Radak et al., 2001; Vita et al., 2020), the diaphragm (Vita et al., 2020), 
heart (Booth et al., 2018; Ludlow et al., 2017; Ludlow et al., 2012; Sadeghi-Tabas et al., 2020; 
Saghebjoo et al., 2019; Werner et al., 2008), aorta (Werner et al., 2009), liver (Ludlow et al., 2012), 
brain (prefrontal cortex and hippocampus) (Mychasiuk et al., 2016), hippocampal neural precursor 
cells (Wolf et al., 2011) and PBMCs (Werner et al., 2009) from Wistar rats, Sprague Dawley rats, 
Wistar Kyoto rats, C57/BL6 mice, CAST/Ei J mice and Mdx mice. Six studies used male mice (Booth et 
al., 2018; de Carvalho Cunha et al., 2018; Radak et al., 2001; Sadeghi-Tabas et al., 2020; Werner et 
al., 2009; Werner et al., 2008), two used female (Ludlow et al., 2017; Wolf et al., 2011), three used 
male and female mice (Ludlow et al., 2012; Mychasiuk et al., 2016; Saghebjoo et al., 2019), and one 
was unspecified (Vita et al., 2020). Of the studies that examined the influence of a single bout of 
exercise (30 min, 42 min or one day of training) on Tert mRNA or telomerase activity, two studied 
the heart using treadmill protocols (Ludlow et al., 2017; Saghebjoo et al., 2019) and one studied the 
brain using voluntary wheel running (Mychasiuk et al., 2016). Training studies mainly involved the 
use of treadmill running (n = 5) or voluntary wheel running (n = 5), and two utilised swimming (de 
Carvalho Cunha et al., 2018; Radak et al., 2001). Exercise intensities ranged from self-selected 
(voluntary wheel running) to moderate to high intensity interval training (Table 2). 
 
3.3 Risk of bias 
A summary of the risk of bias appraisal is displayed in Figure 2. Of the 24 eligible studies, two scored 
nine (Cheung et al., 2019; Puterman et al., 2018) and 10 (Booth et al., 2018; Duan et al., 2016), five 
 11 
scored 12 (de Carvalho Cunha et al., 2018; Ho et al., 2012; Mychasiuk et al., 2016; Saghebjoo et al., 
2019; Vita et al., 2020), four scored 13 (Sadeghi-Tabas et al., 2020; Werner et al., 2009; Werner et 
al., 2008; Werner et al., 2019), three scored 14 (Noorimofrad and Ebrahim, 2018; Radak et al., 2001; 
Saki et al., 2016), one scored 15 (Wolf et al., 2011) and 16 (Ludlow et al., 2012), three scored 17 
(Ludlow et al., 2017; Nickels et al., 2020; Zietzer et al., 2017), one scored 18 (Chilton et al., 2014), 19 
(Laye et al., 2012) and 21 (Cluckey et al., 2017) out of a cumulative total of 21 (1–3 in seven 
domains) on the Cochrane Risk of Bias Tool. After pooling the studies, the overall risk of bias score 
was 332 (out of a possible 168–504) indicating a moderate overall risk of bias. 
 
3.4 Meta-analysis 
3.4.1 Meta-analysis on TERT gene expression and telomerase activity after a single bout of exercise 
Five studies involving eleven comparisons provided data on the influence of a single bout of exercise 
on TERT gene and telomerase activity (Chilton et al., 2014; Cluckey et al., 2017; Ludlow et al., 2017; 
Saghebjoo et al., 2019; Zietzer et al., 2017). Three were human trials examining the influence of 
exercise on TERT expression and telomerase activity in whole blood leukocytes, PBMCs or isolated 
leukocyte subsets, whereas Ludlow et al. (2017) analysed heart Tert and telomerase activity in mice 
and Saghebjoo et al. (2019) analysed heart telomerase activity in rats. The meta-analysis found a 
single bout of exercise significantly increased TERT expression and telomerase activity (N = 142, 
overall effect – SMD [95%CI]: 1.19 [0.41 – 1.97], p = 0.003, Figure 3). The studies displayed high 
heterogeneity (87%). 
 
3.4.2 Meta-analysis on TERT gene expression and telomerase activity after chronic exercise training 
Ten studies, including 16 comparisons, were included in the meta-analysis examining the influence 
of chronic exercise training on TERT expression and telomerase activity. Seven studies were human 
trials analysing leukocyte or PBMC TERT expression or telomerase activity, while the other three 
were rodent studies including analyses involving heart, skeletal muscle and liver samples (de 
Carvalho Cunha et al., 2018; Ludlow et al., 2012; Sadeghi-Tabas et al., 2020). The results from this 
meta-analysis indicated that chronic exercise training increased telomerase activity (N = 337, overall 
effect – SMD [95%CI]: 0.31 [0.03 – 0.60], p = 0.03, Figure 4), albeit to a lesser extent than a single 
bout of exercise training. Studies exhibited moderate heterogeneity (I2 = 55%). 
 
3.5 Publication bias 
The funnel plots from meta-analytical findings on the influence of a single bout of exercise and 
chronic exercise training on TERT expression and telomerase activity are illustrated in Figure 5A and 
 12 
5B, respectively. Although only a modest number (n = 5) of heterogenous trials (I2 = 87%) were 
included making the assessment of publication bias problematic, the funnel plot of acute exercise 
trials was somewhat asymmetrical (Figure 5A). The chronic exercise training interventions did not 
show marked signs of publication bias, as most studies were clustered around the mean (Figure 5B). 
 
3.6 Endurance athletes possess higher leukocyte TERT expression and telomerase activity 
Four cross-sectional studies that analysed TERT and telomerase activity in endurance athletes and 
controls were retrieved and screened, but were excluded from the meta-analysis because they did 
not meet the inclusion criteria (e.g. did not analyse TERT/telomerase after an exercise intervention) 
(Supplementary Table 3). Considering endurance athletes engage in regular exercise training, have 
superior cardiorespiratory fitness and relatively longer leukocyte telomeres compared to inactive 
controls (Abrahin et al., 2019; Denham et al., 2013), leukocyte/PBMC TERT and telomerase activity 
fold-difference data between athletes and controls were extracted from these studies and 
presented in Figure 6. Based on these investigations, endurance athletes, on average, exhibited 
increasedleukocyte TERT expression or PBMC telomerase activity compared to their inactive peers. 
 
4.0 Discussion 
Telomeres are evolutionary conserved guardians of the genome and telomere shortening is one of 
the inevitable hallmarks of ageing somatic cells. Telomerase-based therapies hold enormous 
potential to combat age-related diseases and slow biological ageing, given that their administration 
delays replicative senescence in cultured cells and extends health and lifespan of rodents. Although 
TERT gene therapy trials are currently underway, clinical use of telomerase-based therapies in 
humans is most likely years away. As such, inexpensive and modifiable lifestyle factors that 
modulate telomerase should also be considered to prevent telomere attrition and premature 
biological ageing. The major findings of this systematic review and meta-analysis were that both a 
single bout of exercise training and chronic long-term exercise training increases TERT gene 
expression and telomerase activity. A secondary observation highlighted that endurance athletes 
exhibited increased TERT and telomerase activity in peripheral blood compared to inactive controls, 
which is consistent with the meta-analytical findings from the chronic exercise training studies. 
The influence of exercise training on telomere biology has been scrutinised as early as 2001 (Radak 
et al., 2001). Since then, numerous studies have revealed positive associations between physical 
activity levels, exercise training and athletic status with telomere length and telomere-regulating 
molecules (Abrahin et al., 2019; Denham et al., 2016a; Lin et al., 2019; Mundstock et al., 2015). 
Despite rodent studies offering insight into some of the molecular mechanisms by which exercise 
 13 
maintains telomeres (Werner et al., 2009; Werner et al., 2008), whether exercise training attenuates 
telomere attrition in humans has not yet been comprehensively assessed. Nonetheless, increased 
telomerase activity has been posited as one of the main mechanisms that could underpin the 
observed links between exercise training and telomere length preservation. 
A single bout of exercise induces considerable physiological stress that leads to exercise-induced 
adaptations and enhanced physical performance. This systematic review and meta-analysis 
identified five studies that examined the influence of a single bout of exercise training in human 
peripheral blood cells and in mouse heart tissue. A single bout of exercise significantly increased 
TERT gene expression and telomerase activity in rodent heart tissue and human leukocytes (a large 
effect size: 1.19). Interestingly, telomerase activity was up-regulated immediately after the cessation 
of exercise training in humans (Werner et al., 2019; Zietzer et al., 2017), whereas TERT gene 
expression was only increased one-hour post exercise training (Chilton et al., 2014; Cluckey et al., 
2017) and remained elevated for at least 90 min after (Cluckey et al., 2017). An interpretation of 
these findings is that whilst telomerase activity is rapidly up-regulated by exercise training, the 
increased TERT gene expression that would support telomerase production is delayed to at least one 
hour after training has ceased. All of the acute exercise studies included in this particular analysis 
investigated aerobic exercise training (i.e. treadmill running or cycling). One human investigation 
noted a sex-specific trend in the acute exercise-induced increase in leukocyte TERT expression, such 
that young men displayed significantly up-regulated TERT that was not observed in their female 
peers (Cluckey et al., 2017). Although not statistically significant, an opposite observation was noted 
in one of the rodent studies that indicated telomerase activity tended to increase in the heart from 
exercised females compared to males (Saghebjoo et al., 2019). Therefore, results on sex-specific 
effects on exercise-induced TERT gene expression and telomerase activity are mixed but warrant 
attention in future investigations. Based on the limited evidence, there does not appear to be any 
exercise mode-specific effects on TERT expression, yet according to one study, a single session of 
resistance training does not appear to increase PBMC telomerase activity (Werner et al., 2019). 
Given the importance of resistance training for maintaining skeletal muscle, bone density and 
functionality, further analyses using other exercise prescriptions to determine potential influences 
they may have on TERT/telomerase activity are encouraged. 
Whereas a single exercise session causes considerable cellular stress, repeated exposure to exercise 
training induces a multitude of exercise adaptations that improve performance and reduce the risk 
of age-related chronic disease. Based on findings from the eligible studies including those that 
analysed skeletal muscle, heart, liver, brain and leukocytes (whole blood and PBMCs), chronic 
exercise training also increases TERT gene expression and telomerase activity, albeit to a lesser 
 14 
extent than immediate responses (moderate effect size: 0.31). Notably, the majority of exercise 
training studies encompassed aerobic exercise interventions and the only one that solely focused on 
resistance training utilised a form that has an emphasis on muscular endurance which would also 
stress the aerobic energy system (Nickels et al., 2020). The present study indicated that long-term 
exercise training increases PBMC telomerase activity and leukocyte TERT expression in humans, 
which is further supported by the increased TERT/telomerase activity observed in human athletes 
relative to healthy controls. This long-term adaptation may ultimately delay biological ageing 
through telomere length maintenance. The immediate increase in leukocyte TERT and telomerase 
activity from each exercise session could lead to sustained expression and activity over time. 
Although yet to be experimentally validated, it is reasonable to suggest that habitual exercise 
training is required to maintain TERT expression, telomerase activity and telomere integrity, and that 
sedentarism must be avoided to promote healthy ageing. It should be a priority of future studies to 
identify the optimal exercise prescription (e.g. length of intervention, frequency, intensity, duration 
and modes of exercise [strength versus aerobic training]) that could be conducive to TERT-mediated 
telomere maintenance. 
There are tissue-specific effects of long-term exercise training on telomere length, such that 
telomere shortening is attenuated in the heart, aorta and liver (Ludlow et al., 2012; Werner et al., 
2009; Werner et al., 2008) and leukocyte telomeres tend to be longer in individuals who are 
physically active or athletes compared to inactive counterparts (Denham et al., 2016a; Lin et al., 
2019). Despite the links between relatively long leukocyte telomeres, aerobic fitness and exercise 
training, skeletal muscle telomeres do not appear to be preserved by exercise training in humans 
(Hiam et al., 2020; Ponsot et al., 2008; Rae et al., 2010), although some have shown positive findings 
(Osthus et al., 2012). They are, however, inversely correlated to exercise training volumes in healthy 
athletes and shorter in overtrained athletes (Collins et al., 2003; Kadi et al., 2008; Rae et al., 2010). 
Furthermore, long-term exercise training (voluntary wheel running) accelerates skeletal muscle 
telomere shortening but increases telomerase activity in mice (Ludlow et al., 2012). Increased 
telomerase activity is an established characteristic of small mammals compared to larger species 
with very low or undetectable levels (Gomes et al., 2011; Seluanov et al., 2007). Both TERT gene 
expression and telomerase activity were not detected in human skeletal muscle samples in one 
exercise trial (Laye et al., 2012), whereas some rodent studies have noted changesin response to 
chronic exercise training (de Carvalho Cunha et al., 2018; Ludlow et al., 2012). Considering these 
tissue-specific effects, it would be advantageous to determine the influence of both a single bout 
and chronic exercise on telomerase activity in other tissues (e.g. lung, brain, etc.) and establish the 
telomere dynamics. 
 15 
4.1.3 Endurance athletes 
According to recent meta-analytical findings, endurance athletes possess longer leukocyte 
telomeres, on average, than their non-athletic peers (Abrahin et al., 2019). In addition to our 
primary meta-analyses, the search strategy revealed three investigations that analysed leukocyte 
TERT expression or telomerase activity in endurance athletes compared to healthy controls. 
Collectively, endurance athletes tended to have higher leukocyte TERT or telomerase activity 
compared to controls. These cross-sectional studies further support the premise that exercise 
training up-regulates TERT expression and telomerase activity, considering endurance athletes 
engage in regular exercise training. Furthermore, the increased leukocyte TERT/telomerase activity 
observed in endurance athletes could partly account for their longer leukocyte telomeres compared 
to inactive individuals observed previously (Abrahin et al., 2019). 
There seems to be an effect of ageing on the exercise-related increase in leukocyte TERT and 
telomerase activity. Specifically, young and middle-aged athletes exhibited higher levels of TERT and 
telomerase activity compared to control groups (mean fold-difference: 1.8–4.2-fold) (Denham et al., 
2016b; Hagman et al., 2020; Werner et al., 2009), whereas similar levels were observed in older 
adult athletes and age-matched inactive controls (Hagman et al., 2020). It was not the primary aim 
of the meta-analysis, yet this finding could be explained by the reduced training volumes reported 
by elderly endurance athletes compared to their younger peers (Hagman et al., 2020). Training once 
a week may not be enough to maintain physical fitness and TERT-mediated telomere maintenance, 
rather consistent training closer to frequencies identified in the majority of human exercise trials 
examined in this meta-analysis maybe necessary (i.e. 3–5 days per week). Alternatively, there could 
be age-associated reductions in the response of leukocyte TERT expression and telomerase activity 
to exercise training. This hypothesis should be experimentally tested in future investigations. 
The meta-analyses presented here included data from human and rodent experiments analysing the 
influence of exercise on TERT mRNA and telomerase activity in healthy non-cancerous tissues, which 
is a strength of the work. Due to the relatively modest number of experimental trials in acute (n = 5) 
and long-term exercise training studies (n = 10), subgroup analyses were not performed. It was not 
the intended purpose of the current meta-analysis to perform sub-group analyses. Nonetheless, the 
analyses included all relevant and available literature, which contributed to the scientific rigour and 
ensured the generalisability of the results from our work. We did, however, summarise the 
increased TERT and telomerase activity findings from studies analysing differences between 
endurance athletes and controls, which complemented the meta-analytical findings. Although 
rodent telomeres are much longer than humans’, rodents exhibit accelerated telomere shortening 
over time that coincides with their shorter lifespan (consistent with other mammals) (Whittemore et 
 16 
al., 2019). However, the inclusion of human and rodent experiments did increase the heterogeneity, 
particularly in the acute exercise trials (I2 = 87%). Telomerase activity was quantified in numerous 
rodent tissues unlike human investigations that almost exclusively analysed whole blood or isolated 
leukocyte subtypes. The only exception was from Laye et al. (2012), where PBMC and skeletal 
muscle TERT and telomerase activity were examined in response to exercise. There seems to be 
tissue-specific effects of exercise on telomerase activity. For instance, it is up-regulated in PBMCs 
after a seven-day ultra-marathon but is not detectable in human skeletal muscle (Laye et al., 2012). 
Therefore, tissue specific meta-analyses would have been beneficial, but this was not the main 
objective of the project and would be restricted to a very limited number of studies. Although the 
researchers made a reasonable effort to retrieve all data from others to include all eligible studies in 
the meta-analyses, data were not obtained from eight papers. Despite this limitation, six of the eight 
studies showed positive findings (exercise increased TERT mRNA/telomerase activity) (summarised 
in Supplementary Table 2). Therefore, it is unlikely that their inclusion would have significantly 
impacted the major findings of our meta-analyses. 
In conclusion, the meta-analytical findings from the present study indicate that both a single bout of 
exercise and chronic exercise training increases TERT expression and telomerase activity in tissues 
where they are detectable. Future work should examine tissue-specificity of exercise-induced 
telomerase activity, the optimal exercise mode and prescription that modulates telomerase activity, 
and the time-course of changes in context with ageing. These findings will help refine physical 
activity guidelines and recommendations for healthy biological ageing through telomerase-mediated 
telomere maintenance. 
 
Acknowledgements 
The authors thank the researchers who shared their data to support the meta-analyses in the 
present study. 
 
Funding 
This research did not receive any specific grant from funding agencies in the public, commercial, or 
not-for-profit sectors. 
 
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Werner, C., Hanhoun, M., Widmann, T., Kazakov, A., Semenov, A., Pöss, J., Bauersachs, J., Thum, T., 
Pfreundschuh, M., Müller, P., Haendeler, J., Böhm, M., Laufs, U., 2008. Effects of physical 
exercise on myocardial telomere-regulating proteins, survival pathways, and apoptosis. J Am 
Coll Cardiol 52, 470-482. 
Werner, C.M., Hecksteden, A., Morsch, A., Zundler, J., Wegmann, M., Kratzsch, J., Thiery, J., Hohl, M., 
Bittenbring, J.T., Neumann, F., Böhm, M., Meyer, T., Laufs, U., 2019. Differential effects of 
endurance, interval, and resistance training on telomerase activity and telomere length in a 
randomized, controlled study. Eur Heart J 40, 34-46. 
Whittemore, K., Vera, E., Martinez-Nevado, E., Sanpera, C., Blasco, M.A., 2019. Telomere shortening 
rate predicts species life span. Proc Natl Acad Sci U S A 116, 15122-15127. 
 22 
Wolf, S.A., Melnik, A., Kempermann, G., 2011. Physical exercise increases adult neurogenesis and 
telomerase activity, and improves behavioral deficits in a mouse model of schizophrenia. 
Brain Behav Immun 25, 971-980. 
Zhang, J.M., Zou, L., 2020. Alternative lengthening of telomeres: from molecular mechanisms to 
therapeutic outlooks. Cell Biosci 10, 30. 
Zhu, J., Wang, H., Bishop, J.M., Blackburn, E.H., 1999. Telomerase extends the lifespan of virus-
transformed human cells without net telomere lengthening. Proc Natl Acad Sci U S A 96, 
3723-3728. 
Zietzer, A., Buschmann, E.E., Janke, D., Li, L., Brix, M., Meyborg, H., Stawowy, P., Jungk, C., 
Buschmann, I., Hillmeister, P., 2017. Acute physical exercise and long-term individual shear 
rate therapy increase telomerase activity in human peripheral blood mononuclear cells. Acta 
Physiol (Oxf) 220, 251-262. 
 
 23 
Table 1. The influence of exercise on TERT and telomerase activity in non-cancerous tissues (humans). 
Reference Populationa,b,c Training 
status 
VO2max 
(ml.kg-1.min1) 
Tissue Analysis Method Exercise triald,e,f,g 
(Nickels et al., 
2020) 
23 Healthy individuals, 
F (16)/M (7), 
51.5 ± 4.9 y 
Untrained ? Whole blood TERT mRNA qPCR Chronic resistance 
exercise (group) 
training, 
12 weeks, 
Low (high 
repetitions), 
2 
(Werner et al., 
2019) 
15 Healthy individuals, 
F (7)/M (8), 
24.5 ± 1.3 y 
untrained 41.4 ± 6.3 PBMC Telomerase 
activity 
TRAP assay Acute treadmill 
running, 
45-min, 
maximum. 
(Werner et al., 
2019) 
15 Healthy individuals, 
F (7)/M (8), 
untrained 41.4 ± 6.3 CD14+ leukocytes Telomerase 
activity 
TRAP assay Acute treadmill 
running, 
 24 
24.5 ± 1.3 y 45-min, 
maximum. 
(Werner et al., 
2019) 
15 Healthy individuals, 
F (7)/M (8), 
24.5 ± 1.3 y 
untrained 41.4 ± 6.3 CD34+ leukocytes Telomerase 
activity 
TRAP assay Acute treadmill 
running, 
45-min, 
maximum. 
(Werner et al., 
2019) 
15 Healthy individuals, 
F (7)/M (8), 
24.5 ± 1.3 y 
untrained 41.4 ± 6.3 PBMC Telomerase 
activity 
TRAP assay Acute circuit 
resistance exercise 
training (strength 
endurance), 
45 min, 
high-intensity (16 
– 20 reps with 
20RM) 
(Werner et al., 
2019) 
15 Healthy individuals, 
F (7)/M (8), 
untrained 41.4 ± 6.3 CD14+ leukocytes Telomerase 
activity 
TRAP assay Acute circuit 
resistance exercise 
 25 
24.5 ± 1.3 y training (strength 
endurance), 
45 min, 
high-intensity (16 
– 20 reps with 
20RM) 
(Werner et al., 
2019) 
15 Healthy individuals, 
F (7)/M (8), 
24.5 ± 1.3 y 
untrained 41.4 ± 6.3 CD34+ leukocytes Telomerase 
activity 
TRAP assay Acute circuit 
resistance exercise 
training (strength 
endurance), 
45 min, 
high-intensity (16 
– 20 reps with 
20RM) 
(Werner et al., 
2019) 
26 Healthy individuals, 
F (17)/M (9), 
50.2 ± 7.4 y 
untrained 35.3 ± 6.3 PBMC Telomerase 
activity 
TRAP assay Chronic aerobic 
endurance 
training, 
6 months, 
 26 
45 min @ 40–60% 
HRR, 
3 
(Werner et al., 
2019) 
29 Healthy individuals, 
F (19)/M (10), 
48.4 ± 6.5 y 
untrained 35.1 ± 5.0 PBMC Telomerase 
activity 
TRAP assay Chronic aerobic 
endurance 
training, 
6 months, 
45 min @ 40–60% 
HRR, 
3 
(Werner et al., 
2019) 
34 Healthy individuals, 
F (20)/M (14), 
48.1 ± 7.5 y 
untrained 35.3 ± 5.3 PBMC Telomerase 
activity 
TRAP assay Chronic aerobic 
endurance 
training, 
6 months, 
45 min @ 40–60% 
HRR, 
3 
 27 
(Cheung et al., 
2019) 
136 Chinese women 
survivors of domestic 
abuse from their intimate 
partner, 
F, 
42 ± 8.7 y 
? ? PBMC Telomerase 
activity 
TeloTAGGG 
Telomerase 
PRC ELISAPLUS 
Chronic Qigong 
training, 
22 weeks, 
low, 
2 
(Puterman et al., 
2018) 
34 Family caregivers, 
F (30)/M (4), 
59.3 ± 5.7 y 
untrained 23.7 ± 5.8 PBMC Telomerase 
activity 
Digital 
Droplet PCR 
Chronic aerobic 
training, 
24 weeks, 
20–30 min @ low–
moderate, 
3–5 
(Noorimofrad and 
Ebrahim, 2018) 
15 Healthy student 
volunteers, 
M, 
19.5 ± 1.1 y 
untrained ? PBMC Telomerase 
activity 
Quantitative 
Telomerase 
Detection 
(QTD) 
Chronic aerobic 
training (cycling), 
9 weeks, 
high intensity 
interval training, 
 28 
3 
(Zietzer et al., 
2017) 
26 Healthy volunteers, 
F (13)/M (13), 
23.37 ± 1.85 y 
? ? PBMC Telomerase 
activity 
TRAPezeTelomerase 
detection kit 
Acute treadmill 
exercise, 
35 min, 
low–moderate 
(Cluckey et al., 
2017) 
Recreationally active 
healthy individuals (11 
young and 8 older), 
F (10)/M 9, 
Young: 22 ± 2 y; older: 60 ± 
2 y 
untrained Young: 38.1 
± 6.3 
Old: 29.2 ± 
6.1 
PBMC TERT mRNA qPCR Acute cycling, 
30 min, 
high intensity 
interval training 
(Saki et al., 2016) 10 Outpatients with a 
history of myocardial 
infarction, 
M, 
57.3 ± 5.56 y 
? ? PBMC Telomerase 
activity 
Quantitative 
Telomerase 
Detection Kit 
(qPCR) 
Chronic aerobic 
and resistance 
training, 
8 weeks, 
Moderate 
intensity, 
 29 
3 
(Duan et al., 2016) 43 Healthy individuals, 
F (27)/M (16), 
59.58 ± 5.56 y 
untrained ? PBMC Telomerase 
activity 
Human 
telomerase 
ELISA 
Chronic, 
Tai Chi training, 
6 months, 
low, 
5 
(Chilton et al., 
2014) 
22 Healthy individuals, 
M, 
24 ± 7.3 y 
? 49.3 ± 4.7 Whole blood 
CD4+CD45RO+ T cell 
CD8+CD45RA+ T cell 
TERT mRNA Microarray 
and qPCR 
Acute treadmill 
running, 
30-min, 
80% of VO2max 
(ml.kg-1.min-1) 
(Laye et al., 2012) 9 Ultramarathon runners, 
F (1)/M (8), 
44 ± 2 y 
trained 58.2 ± 3.1 PBMC Tert mRNA 
Telomerase 
qPCR 
TRAPeze RT 
Telomerase 
Detection Kit 
Chronic aerobic 
exercise, 
7 days, 
moderate, 
 30 
7 
(Ho et al., 2012) 27 Individuals with chronic 
fatigue, 
F(25)/M (2), 
42.1 ± 7.3 y 
? ? PBMC Telomerase 
activity 
TeloTAGGG 
Telomerase 
PCR ELISA 
Chronic Qigong 
training, 
4 months, 
low, 
2 
Legend: n/a, not available; VO2max, maximum oxygen uptake; 1RM, one repetition maximum; HRR, heart rate reserve; ?, unknown or not reported. 
a N and participant attributes 
b Sex (M/F) 
c Age at the beginning of the exercise intervention 
d Mode of exercise 
e length of intervention 
f intensity 
g frequency per week (chronic training studies only) 
 
 
 31 
Table 2. The influence of exercise on TERT and telomerase activity in non-cancerous tissues (rodents). 
Reference Populationa,b,c,d Tissue Analysis Method Exercise triale,f,g,h 
(Vita et al., 2020) Mdx and WT mice, 
20, 
?, 
4–5 weeks 
Skeletal muscle 
(gastrocnemius and 
tibialis anterior) 
Diaphragm 
TERT protein 
Telomerase 
activity 
Immunoblot 
Telo TAGGG 
Telomerase 
PCR ELISA Kit 
Chronic treadmill 
training, 
8–10 weeks, 
12 m.min-1, 
2 
(Sadeghi-Tabas et al., 2020) Wistar rats, 
18, 
M, 
12 weeks 
Heart Telomerase 
activity 
Telo TAGGG 
Telomerase 
PCR ELISA Kit 
Chronic treadmill 
training, 
8 weeks, 
40–95% of VO2max 
(ml.kg-1.min-1), 
5 
(Saghebjoo et al., 2019) Wistar rats, 
28, 
Heart Telomerase 
activity 
Telo TAGGG 
PCR ELISA Kit 
Acute treadmill 
training, 
42 min, 
 32 
M (14)/F (14), 
8 weeks 
high-intensity 
interval training 
(long or short 
intervals) 
(de Carvalho Cunha et al., 
2018) 
C57BL/6 mice, 
8, 
M, 
12 months 
Skeletal muscle Tert mRNA qPCR Chronic aerobic 
training, 
12 weeks, 
low to high 
intensity, 
3 
(Booth et al., 2018) Wistar Kyoto rats, 
22–24 in each group (control, 
restricted and reduced – growth in 
utero), 
M, 
5–20 weeks 
Heart Tert mRNA qPCR Chronic treadmill 
training, 
4 weeks, 
15 m.sec-1, 
5 
 33 
(Ludlow et al., 2017) C47BL/6J mice, 
10, 
F, 
6 weeks 
Heart Tert mRNA 
Telomerase 
activity 
qPCR 
TRAP 
Quantitative 
Telomerase 
Detection kit 
Acute treadmill, 
30 min, 
70% of peak speed 
reached during 
incremental 
treadmill testing 
(Mychasiuk et al., 2016) Sprague Dawley rats, 
38, 
M+F, 
1 month 
Prefrontal cortex 
Hippocampus 
Tert mRNA qPCR Acute/Chronic 
aerobic exercise, 
1 – 7 days, 
?, 
VWR 
(Ludlow et al., 2012) CAST/Ei J mice, 
21, 
M+F, 
7–10 weeks 
Heart 
Liver 
Skeletal muscle 
Tert mRNA 
Telomerase 
qPCR 
Quantitative 
Telomerase 
Detection Kit 
Chronic aerobic 
exercise, 
1 year, 
?, 
VWR 
 34 
(Wolf et al., 2011) C57BL/6 mice (control and those who 
received 
polyriboinosinicpolyribocytidylic acid 
[Polyl:C]), 
18 per group, 
F, 
50 days 
Hippocampal neural 
precursor cell 
Telomerase 
activity 
TRAP ELISA Kit Chronic aerobic 
training, 
10 days, 
?, 
VWR 
(Werner et al., 2009) C57/BL6 mice, 
8 per group, 
M, 
8 weeks 
Aorta Telomerase 
activity 
TERT protein 
Quantitative 
repeat 
amplification 
Western Blot 
Chronic aerobic 
training, 
21 days, 
?, 
VWR 
(Werner et al., 2009) C57/BL6 mice, 
6 per group, 
M, 
8 weeks 
PBMC Telomerase 
activity 
TERT protein 
Quantitative 
repeat 
amplification 
Western Blot 
Chronic aerobic 
training, 
21 days, 
?, 
 35 
VWR 
(Werner et al., 2008) C57/BL6 mice, 
8 per group, 
M, 
8 weeks 
Left ventricle Telomerase 
activity 
TERT protein 
Quantitative 
repeat 
amplification 
Western Blot 
Chronic aerobic 
training, 
21 days, 
?, 
VWR 
(Radak et al., 2001) Wistar rats, 
12, 
M, 
12 weeks 
Skeletal muscle Telomerase 
activity 
Telomerase 
PCR ELISA Kit 
Chronic aerobic 
training 
(swimming), 
8 weeks, 
?, 
5 
Legend: n/a, not available; VO2max, maximum oxygen uptake; 1RM, one repetition maximum; HRR, heart rate reserve; VWR, voluntary wheel running; ?, 
unknown or not reported. 
a Animal (rat/mouse) 
b Number in the exercise arm of the trial 
 36 
c Sex (M/F) 
d Age at the beginning of the exercise intervention 
e Type of exercise 
f Length of intervention 
g Intensity 
h Frequency per week (chronic training studies only)
 37 
Figure 1. Prisma diagram. 
 
 
 
From: Moher D, Liberati A, Tetzlaff J, Altman DG, The PRISMA Group (2009). Preferred Reporting Items for Systematic Reviews and Meta-
Analyses: The PRISMA Statement. PLoS Med 6(7): e1000097. doi:10.1371/journal.pmed1000097 
 
For more information, visit www.prisma-statement.org. 
 
PRISMA 2009 Flow Diagram 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Records identified through 
database searching 
(n = 1700) 
Sc
re
en
in
g 
In
clu
de
d 
El
ig
ib
ili
ty
 
Id
en
tif
ica
tio
n 
Additional records identified 
through other sources 
(n = 1) reference list 
Records after duplicates removed 
(n = 530) 
Records screened 
(n = 530) 
Records excluded 
(n = 489) 
 
Full-text articles assessed 
for eligibility 
(n = 41) 
Full-text articles excluded, with 
reasons 
(n = 17) 
• 8 – Did not analyse TERT or 
telomerase after exercise. 
• 4 – Included another lifestyle 
modification in addition to 
exercise 
• 1 – in vitro experiment 
• 1 – Cancerous tissue analysed 
• 1 – Full-text not written in 
English 
• 1 – An RCT protocol (no data) 
• 1 – did not assess cellular 
telomerase activity 
Studies included in 
qualitative synthesis 
(n = 24) 
Studies included in 
quantitative synthesis 
(meta-analysis) 
(n = 15) 
 38 
 
 
 
 
 
 
 
Figure 2. Risk of bias appraisal. Studies were ranked from low (1), moderate (2) or high (3) risk of 
bias in seven domains using the Cochrane risk of bias tool. 
 
 
 
 
 
 
 
 
 
 39 
 
Figure 3. The influence of a single bout of exercise on telomerase reverse transcriptase gene 
expression and telomerase activity. Chi2 = 74.70, df = 10 (p < 0.00001); I2 = 87%; overall effect: Z = 
3.00 (p = 0.003). Data are presented as the standardised mean difference (SMD) with 95% 
confidence intervals (CI). The crossed diamond indicates the overall effect (SMD). Minor ticks on the 
x axis are at -1.4, -0.8, -0.5, -0.2, 0, 0.2, 0.5, 0.8, 1.4, respectively. 
 
 40 
 
Figure 4. The influence of chronic exercise training on telomerase reverse transcriptase gene 
expression and telomerase activity. Chi2 = 33.01, df = 15 (p = 0.005); I2 = 55%; overall effect: Z = 2.19 
(p = 0.03). Data are presented as the standardised mean difference (SMD) with 95% confidence 
intervals (CI). The crossed diamond indicates the overalleffect (SMD). Minor ticks on the x axis are at 
-1.4, -0.8, -0.5, -0.2, 0, 0.2, 0.5, 0.8, 1.4, respectively. 
 
 41 
 
Figure 5. Funnel plots. The funnel plots are from studies investigating a single bout of exercise (A) 
and chronic exercise training (B) on telomerase reverse transcriptase gene expression and 
telomerase activity. Data are presented as the standard error of the standardised mean difference 
(SMD) over the SMD. 
 42 
 
Figure 6. Increased TERT gene expression and telomerase activity in endurance athletes. Data are 
expressed as mean fold-difference of leukocyte TERT mRNA or PBMC telomerase activity between 
endurance athletes and controls. The mean ± SD age of athletes in each study are shown under the 
reference with the n annotated to the bar graphs. Gene expression or telomerase activity is 
expressed as the mean fold difference (FD). 
 
 
 
 
 
 
 
 
 
 43 
Appendices 
Supplementary Table 1. Search strategy and results. 
Databases Search Search terms Results 
PubMed* 
Science Direct 
(Elsevier) 
Scopus 
Embase 
 
1 (Exercise OR “physical exercise” OR “physical activity” OR 
exercise[MeSH Terms]) AND (hTERT OR TERT OR telomerase 
OR “telomerase reverse transcriptase”) 
279^ 
2 (Exercise OR “physical exercise” OR “physical activity” OR 
exercise[MeSH Terms] OR “aerobic training” OR “endurance 
training”) AND (hTERT OR TERT OR telomerase OR 
“telomerase) 
625 
3 ("resistance training" OR "strength training" OR "power 
training") AND (hTERT OR TERT OR telomerase OR 
"telomerase reverse transcriptase") 
190 
4 (Exercise OR “physical exercise” OR “physical activity” OR 
exercise[MeSH Terms] OR “aerobic training” OR “endurance 
training” OR “resistance training” OR “strength training” OR 
“power training”) AND (hTERT OR TERT OR telomerase OR 
“telomerase reverse transcriptase”) 
606 
PubMed and Scopus searches restricted to work written in English. Title and abstract searches were 
conducted for PubMed, Scopus (journal source) and Embase (article – publication type). Science 
Direct search was conducted with title, abstract and keyword, and restricted to ‘research articles’ 
and ‘short communications’. Parentheses for entire search term were not used for the Scopus 
database search. 
*MeSH Terms used only in PubMed database search. 
^Scopus database was excluded from ‘search 1’ due to retrieval of excessive journals that were 
inappropriate. 
 
 
 
 
 
 
 
 
 
 
 
 
 44 
Supplementary Table 2. Studies that were eligible for inclusion but the necessary data was not 
retrieved. 
Reference Tissue Main finding/s 
Booth, S. A., Wadley, G. D., Marques, F. Z., Wlodek, 
M. E., & Charchar, F. J. (2018). Fetal growth 
restriction shortens cardiac telomere length, but this 
is attenuated by exercise in early life. Physiological 
genomics, 50(11), 956-963. 
 
Heart No statistically significant 
changes in Tert gene 
expression after chronic 
exercise training in mice. 
Mychasiuk, R., Hehar, H., Ma, I., Candy, S., & 
Esser, M. J. (2016). Reducing the time interval 
between concussion and voluntary exercise restores 
motor impairment, short-term memory, and 
alterations to gene expression. European journal of 
neuroscience, 44(7), 2407-2417. 
 
Prefrontal 
cortex & 
Hippocampus 
Chronic exercise increased Tert 
gene expression in mice. 
Saki, B., Bahrami, A., Ebrahim, K., Abedi-Yekta, A., & 
Hedayati, M. (2016). Effect of concurrent training 
on telomere length in patients with myocardial 
infarction: Randomised clinical trial of cardiac 
rehabilitation. Gene Reports, 4, 264-268. 
 
PBMC Chronic concurrent training 
increased telomerase activity 
in patients with a history of 
myocardial infarction. 
Vita, G. L., Aguennouz, M. H., Sframeli, M., Sanarica, 
F., Mantuano, P., Oteri, R., ... & La Rosa, M. (2020). 
Effect of exercise on telomere length and telomere 
proteins expression in mdx mice. Molecular and 
Cellular Biochemistry. 
 
Skeletal 
muscle 
 
 
Diaphragm 
Chronic exercise training 
decreases TERT protein in wild 
type mice. 
 
Chronic exercise training 
increased TERT protein and 
telomerase activity in Mdx 
mice, and telomerase activity 
in wild types. 
 
Werner, C., Fürster, T., Widman, T., Pöss, J., Roggia, 
C., Hanhoun, M., ... & Haendeler, J. (2009). Physical 
Exercise Prevents Cellular Senescence in Circulating 
Leukocytes and in the Vessel 
Wall. Circulation, 120(24), 2438-2447. 
Aorta Chronic exercise training 
increases TERT protein and 
telomerase activity in mice. 
 45 
 
 
Werner, C., Hanhoun, M., Widman, T., Kazakov, A., 
Semenov, A., Pöss, J., ... & Haendeler, J. (2008). 
Effects of physical exercise on myocardial telomere-
regulating proteins, survival pathways, and 
apoptosis. Journal of the American College of 
Cardiology, 52(6), 470-482. 
 
Heart Chronic exercise training 
increases TERT protein and 
telomerase activity in mice. 
Werner, C. M., Hecksteden, A., Morsch, A., Zundler, 
J., Wegmann, M., Kratzsch, J., ... & Böhm, M. 
(2019). Differential effects of endurance, interval, 
and resistance training on telomerase activity and 
telomere length in a randomized, controlled 
study. European heart journal, 40(1), 34-46. 
 
PBMC, 
CD14+ and 
CD34+ 
leukocytes. 
 
PBMC 
A single bout of aerobic 
exercise training increase 
telomerases activity. 
 
 
Chronic aerobic exercise 
(endurance; and interval) 
training increases telomerase 
activity. 
Radak, Z., Taylor, A. W., Sasvari, M., Ohno, H., 
Horkay, B., Furesz, J., ... & Kanel, T. (2001). 
Telomerase activity is not altered by regular 
strenuous exercise in skeletal muscle or by sarcoma 
in liver of rats. Redox Report, 6(2), 99-103. 
 
Skeletal 
muscle 
Chronic exercise training did 
not alter telomerase activity. 
 
 
 
 
 
 
 46 
Supplementary Table 3. Summary of studies examining TERT or telomerase activity in endurance athletes compared to controls. 
Endurance athletesa,b,c,d Controlsa,b,c,d Tissue Reference 
Young: 32, 20.4±0.6, 25/7, ? 
 
Middle-aged: 25, 51.1±1.6, 19/6, ? 
Young: 26, 21.8±2.8, 15/11, ? 
 
Middle-aged: 21, 50.9±7.6, 14/7, ? 
PBMC Werner, C., Fürster, T., Widman, T., Pöss, J., 
Roggia, C., Hanhoun, M., ... & Haendeler, J. 
(2009). Physical Exercise Prevents Cellular 
Senescence in Circulating Leukocytes and in the 
Vessel Wall. Circulation, 120(24), 2438-2447. 
61, 33.7±11.0, 46/15, 58.8±7.6 61, 28.7±10.6, 47/14, 43.7±7.0 Whole 
blood 
leukocytes 
Denham, J., O'Brien, B. J., Prestes, P. R., Brown, 
N. J., & Charchar, F. J. (2016). Increased 
expression of telomere-regulating genes in 
endurance athletes with long leukocyte 
telomeres. Journal of applied 
physiology, 120(2), 148-158. 
Young: 35, 21.6±3.0, 35/0, ? 
 
Older adult: 35, 71.9±3.0, 35/0, ? 
Young: 35, 24.3±3.5, 35/0, ? 
 
Older adult: 35, 70.1±4.1, 35/0, ? 
PBMC Hagman, M., Werner, C., Kamp, K., Fristrup, B., 
Hornstrup, T., Meyer, T., ... & Krustrup, P. 
(2020). Reduced telomere shortening in lifelong 
trained male football players compared to age-
matched inactive controls. Progress in 
Cardiovascular Diseases. 
mean±SD are presented. ?, unknown or not reported. 
a number of participants 
b age (years) 
c sex (M/F) 
 47 
d maximal oxygen uptake (VO2max) 
 
 
 
 
 
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