ALVES_2022 Autonomic response ktb

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Journal of Bodywork & Movement Therapies xxx (xxxx) 1–10
Contents lists available at ScienceDirect
Journal of Bodywork & Movement Therapies
journal homepage: www.elsevier.com/locate/jbmt
Prevention and Rehabilitation
Cardiac autonomic responses to high-intensity kettlebell training in
untrained young women: A pilot study
Sabrina P. Alves a, *, Carla Zimerer a, Richard D. Leite a, b, Letícia Nascimento Santos Neves a,
Camila Moreira a, Luciana Carletti a, b
a Graduate Program in Physical Education, Brazil
b Department of Physical Education and Sports, Federal University of Espírito Santo, Vitória, Espírito Santo, Brazil
A R T I C L E I N F O
Article history:
Received 19 July 2021
Received in revised form 31 October 2022
Accepted 11 December 2022
Keywords:
Autonomic nervous system
Heart rate
Female
High-intensity interval training
Physical fitness
A B S T R A C T
Background: and purpose: The autonomic recovery after exercise provides information about the cardiovascular
overload employed during the training session. The autonomic response over a training course is unclear in ex-
ercises performed at high intensities, such as kettlebell training. The study aimed to characterize the cardiac
autonomic modulation after exercise in three distinct phases of a high-intensity kettlebell training program in
young women.
Methods: Ten women (25.0 ± 2.9 years; 23.4 ± 3.0 kg/m2) were submitted to 10 weeks of training divided into
three phases (three times a week). The autonomic response was measured in the pre-exercise and at 10, 20, and
30 min of recovery and evaluated temporal and linear analysis of heart rate variability (HRV) indices.
Results: vigorous intensity was performed in the sessions (75–86% HRmax). There was a significant reduction of
HRV measured during post-exercise recovery (p 0.05).
Conclusion: The high-intensity kettlebell training program reduces HRV to 30 min of recovery (phases I and II).
In the last phase (III), HRV components returned in 20 min. In addition, the program promoted improvement in
aerobic fitness.
© 20XX
1. Introduction
In the last decade, kettlebell training has been highlighted due to its
ability to increase muscle strength (Chen et al., 2018; Manocchia et al.,
2013; Lake and Lauder 2012; Otto et al., 2012; Jay et al., 2011) and
aerobic capacity (Vancini et al., 2019; Fusi et al., 2017; Falatic et al.,
2015; Williams and Kraemer 2015; Fortner et al., 2014; Thomas et al.,
2014; Budnar et al., 2014; Hulsey et al., 2012; Farrar et al., 2010)
through the use of only simple equipment (a cast-iron weight similar to
a cannonball with a handle) (O'Hara et al., 2012). Short-term sessions
characterize kettlebell training (≤30 min) (Wong et al., 2017; Fusi et
al., 2017; Williams and Kraemer 2015; Budnar et al., 2014; Fortner et
al., 2014; Thomas et al., 2014; Hulsey et al., 2012; Farrar et al., 2010)
involving multiple muscle group exercises. Kettlebell protocols are
* Corresponding author. Center of Sports and Physical Education, Federal
University of Espírito Santo, Goiabeiras Campus, Fernando Ferrari Avenue, 514,
Goiabeiras, 29075-910, Vitória, Espirito Santo, Brazil.
E-mail address: sabrina.pa18.sa@gmail.com (S.P. Alves).
known to be able to generate high intensities of 73–93% maximum
heart rate (HRmax) (Fusi et al., 2017; Williams and Kraemer 2015;
Budnar et al., 2014; Fortner et al., 2014; Thomas et al., 2014; Hulsey et
al., 2012; Farrar et al., 2010) and 56–75% maximum oxygen consump-
tion ( O2max) (Fusi et al., 2017; Williams and Kraemer 2015; Fortner
et al., 2014; Thomas et al., 2014; Farrar et al., 2010), which allows this
type of training to be used as an alternative for high-intensity interval
training (HIIT) (Williams and Kraemer 2015; Fortner et al., 2014; Jay et
al., 2011).
In this context, the acute responses reported in the literature pre-
dominantly explore cardiovascular parameters (HR, O2) to character-
ize the intensity of the sessions (Fusi et al., 2017; Williams and
Kraemer 2015; Fortner et al., 2014; Thomas et al., 2014; Hulsey et
al., 2012; Farrar et al., 2010). However, data on the impact of kettle-
bell training protocols on the autonomic nervous system (ANS) re-
garding the assessment of cardiac autonomic recovery are scarce
(Wong et al., 2017). The evaluation of the post-exercise recovery pe-
riod allows the identification of changes in autonomous cardiac activ-
ity in response to the impact of exercise and monitoring the reestab-
https://doi.org/10.1016/j.jbmt.2022.12.001
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lishment to basal levels, thus revealing the magnitude of the cardiac
stress (e.g., increased HR) caused by exercise (Schaun and Del
Vecchio 2018; Kliszczewicz et al., 2018; Hoshi et al., 2017). There-
fore, the post-exercise period becomes an essential tool for the stud-
ies.
Cardiac autonomic recovery can be measured through heart rate
variability (HRV). The HRV represents the successive oscillations of in-
tervals between consecutive heartbeats in the cardiac cycle (Task Force
1996). The HRV allows for the indirect and non-invasive measurement
of cardiovascular overload caused by exercise (Peçanha et al., 2017,
Task Force 1996). Delayed recovery of cardiac autonomic activity to
baseline reflects a higher sympathetic activity and higher risk and expo-
sure to cardiovascular events (ventricular arrhythmias, sudden cardiac
deaths) (Peçanha et al., 2017; Albert et al., 2000). This risk may dis-
courage the prescription of high-intensity exercises for untrained sub-
jects (Gladwell et al., 2010).
Although studies show that in kettlebell training sessions, the use of
higher loads leads to greater mechanical demand when compared to
lower loads (Levine et al., 2020; Lake and Lauder 2012), the impact of
kettlebell load manipulation on autonomic activity is not yet well estab-
lished. Wong et al. (2017) investigated the acute autonomic response to
kettlebell training in physically active individuals with a predetermined
fixed kettlebell load for beginners (8 kg women and 16 kg men). The
authors reported a reduction in the high-frequency index (HF- parasym-
pathetic activity) and increased low-frequency index (LF- sympathetic
and parasympathetic activities) for 30 min after an exercise session (12
rounds/30:30[s] work-to-rest ratio; 80–90% HR predicted). Addition-
ally, the sympathovagal balance ratio (LF/HF) was increased. However,
there was no recovery of the autonomic activity at baseline levels in
this period.
In this context, information about the autonomic response to kettle-
bell training programs in which the load is individually prescribed has
not yet been reported. Furthermore, one does not know how individual-
ized kettlebell load progression during a training program can impact
the recovery of the autonomic system. Therefore, with progressive
loads, characterization of the cardiac autonomicresponse to this kind of
training can help understand questions about the organization, pre-
scription, and safety of training that may support subsequent studies for
the clinical population.
Additionally, studies on responses to kettlebell training show a
higher proportion of the male population as the sample (45%), followed
by studies with both genders (40%), a smaller percentage only with the
female public (11%) and some studies did not report gender (4%)
(Meigh et al., 2019). This scenario emphasizes the broad context of re-
search in sports science where women are underrepresented (Costello
et al., 2014). Furthermore, given the physiological distinctions between
men and women (e.g., women show lower sympathetic hyperactivity)
(Carere et al., 2022; Koenig and Thayer 2016), the generalization of
studies conducted with an exclusively male sample represents a gap,
suggesting the importance of developing studies at the female public.
Therefore, this study aimed to characterize the cardiac autonomic re-
sponse after exercise in different phases of a high-Intensity kettlebell
training program in untrained young women.
2. Material and methods
2.1. Design
The present study was an experimental design with an interven-
tional period of 10 weeks. The training and data collection were per-
formed in the Center for Research and Extension in Body Movement
Sciences (NUPEM), located at the Federal University of Espírito Santo
(UFES). The procedures started after being approved by the Legal repre-
sentative Research Ethics Committee of the UFES (Approval number:
90506418.7.0000.5542), following the Declaration of Helsinki. The
data collection period occurred in the second half of 2019, from July to
December. Participants were informed about the study's procedures,
aims and were asked to read and sign a consent form. The study had
three assessment moments (before, during, and after the training pro-
gram). In the first week, participants performed pre-training assess-
ments during two visits to the laboratory, with at least 48 h between
tests. Questionnaires, resting blood pressure measures, and aerobic fit-
ness test were performed on the first day. Anthropometric measure-
ments followed on the second day of evaluation. Following a familiar-
ization period, the 10-week training program was initiated. During the
training period, HRV assessments were carried out. At the end of the
program, the participants were re-evaluated in another two days, in the
same order as the beginning (48 h between visits) (Fig. 1).
2.2. Subjects
The participants were selected using a method of convenience sam-
pling. The recruitment of volunteers was announced through posters on
the university campus, institutional email and social media. The enroll-
ment was made through the online form. Initially, 20 healthy young
women (24.5 ± 2.7 years) academic students at the federal university
of Espirito Santo were eligible for intervention. All participants had not
performed regular physical activity or strength training in the previous
three months. The inclusion criteria required subjects to be female,
18–30 years old, have at least three months of previous experience in
resistance training, sufficient physical condition to perform the proto-
col with the cardiologist's medical certificate, normotensive (i.e., rest-
ing systolic blood pressure (SBP)/diastolic blood pressure
(DBP)kg); squat in front of
the wall with shoulder flexion; front squat (8 kg) (Fig. 2). The partici-
pants performed a set of 15 repetitions (rep), with 1-min rest for each
exercise. The length of the sessions was approximately 25 min (total
time). Then, the ten weeks of training began; sessions were distributed
over three weekdays, divided into 3 phases: Phase I (2 weeks), Phase II
(4 weeks), and Phase III (4 weeks) (Fig. 1).
The training sessions were divided into three parts: warm-up, main
part, and cool-down. The 5-min warm-up was composed of whole-body
movements involving the large muscle groups required in the main part
of the session. The exercises used were lunges, hip elevation with
unipodal support, lateral trunk flexion, trunk rotation (15-rep for each
side), trunk extension and flexion (15-rep), the 20-s Farmer's Walk with
two kettlebells (8 and 12 kg). The exercises were performed continu-
ously (i.e., without rest). The 5-min cool-down was composed of the fol-
lowing exercises: seated trunk flexion, seated trunk flexion with the
knee (90°), lying hip flexion, and lying hip rotation. They performed
unilaterally for a duration of 30 s. Both warm-up and cool-down were
performed in the same way during all phases.
During the first phase of the program (Phase I), the main part was
comprised of 2 exercise bouts: a 5-sets kettlebell swing (Fig. 2 E) and a
3-sets front squat (Fig. 2G). Each set lasted the 30s of work followed by
30s of passive rest interval (30:30). The rest interval between bouts was
2min. The total session time was approximately 21min (9 min of proto-
col time). Phase II was started from the 5th week, the main part consist-
ing of 3 bouts of 5-sets. Kettlebell swing and front squat were inter-
spersed, maintaining the 30:30 work rate with a 2-min rest between
bouts. The session lasted approximately 30min (15.55min of protocol
time). Phase III started from the 9th week, and the main part differs
from phase II only on the interval between the bouts, which became
1 min. The total session time was approximately 28min (14.5min of
protocol time). In all phases, participants were encouraged to perform
as many repetitions as a possible per set, both for swing and front squat,
with proper technique maintenance.
Due to a lack of experience with the technique, the participants
started the training with a kettlebell of 8 kg (Tsatsouline 2006). How-
ever, to prescribe the intensity of training in an individualized way, a
standard was adopted, from which the weight of the kettlebell was in-
creased by 4 kg at the same time: assessment of rating of perceived ex-
ertion (RPE), a scale of 0–10 (Borg 1982), ≤5; pace ≥23 rep in all swing
sets (Fusi et al., 2017) and maintenance of the proper technique. Thus,
the kettlebell used, which initially was 8 kg, as suggested for beginners
(Tsatsouline 2006), was increased by 4 kg each time the criteria were
reached (i.e., 8, 12, 16 kg and so it goes on).
2.3.5. Autonomic modulation
HRV was monitored in the last session of each training phase to
avoid the bias of the participants' difficulty in assimilating the tech-
nique during the first sessions of each phase (e.g., slow or incorrect exe-
cution of the exercises). In total, three sessions were monitored during
the training program, before (rest) and after exercise (recovery). The
volunteers were advised to avoid coffee, alcohol and sleep for at least
8 h on the day before the assessment. In a quiet, dimly lit room at a tem-
perature of 22 °C, data collection was conducted, always between 1:00
and 5:00 p.m. Initially, the HRV of rest was registered for 5 min, being
volunteers sat in a chair and relaxed. After the exercise session, the
30 min post-exercise was recorded. HRV records were obtained through
the belt Polar® H10 HR monitor (Polar Electro OY, Kempele, Finland)
(Gilgen-Ammann et al., 2019) with a sampling rate of 500 Hz. In addi-
tion, the sign of HRV was captured via Bluetooth by a smartphone
through the Elite HRV (Elite HRV app, Asheville NC) (Perrotta et al.,
2017).
The data were transferred to the software Kubios HRV Standard 3.0
(Tarvainen et al., 2014) to calculate the HRV indices. The segments
were extracted: pre-exercise (rest before a session - 5min), recovery
(rec) to the 5–10, 15–20, and 25–30 min (last 5 min of each segment)
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Fig. 2. Kettlebell training exercises. Familiarization: (A) Free hip flexion and extension; (B) deadlift; (C) first part of the swing kettlebell; (D) first attempts of kettle-
bell swing movement (pass a towel between the kettlebell handle and hold it with both hands); (E) kettlebell swing; (F) free squat facing wall with hands over head;
(G) front squat kettlebell facing wall.
(Schamne et al., 2019). The intervals between consecutive heartbeats
derived from an electrocardiogram (RR interval series) were analyzed
to remove artifacts, and filtering was used, following an acceptable
limit for artifact correction of a maximum of 5% (Kubios HRV Standard
3.0). The RMSSD index (Root Mean Square of the Successive Differ-
ences) was chosen to represent parasympathetic activity in the time do-
main (Shaffer and Ginsberg 2017, Task Force 1996). The frequency do-
main was based on the Fast Fourier transformation (300s window with
50% overlap). The indices of HF (high frequency – 0.15 a 0.4 Hz) were
used in normalized units (HF n.u. = HF/total power - VLF x 100),
which indicates the respiratory modulation and marker of the action of
the vagus nerve on the heart and LF (low frequency – 0.04 e 0.15 Hz)
(LF n.u. = LF/total power - VLF x 100) to influenced by sympathetic
and parasympathetic activities (Shaffer and Ginsberg 2017, Task Force
1996). The LF/HF ratio was also used to determine sympathovagal bal-
ance (Piccirillo et al., 2009).
2.4. Training load
Considering that kettlebell training studies bring minor details
about the programs and the influence of training load on the cardiac au-
tonomic recovery response after exercise (Michael et al., 2017a;
Manocchia et al., 2013; Lake and Lauder 2012; Otto et al., 2012) infor-
mation about training load was evaluated. The total volume (TV), per-
centage of maximum HR (%HRmáx), the weight of the kettlebell lifted
relative to body mass (%BM), and RPE were assessed. The TV repre-
sents the product between the number of reps, set number, and weight
of the kettlebell used (kg) (reps x sets x load [kg]) (Steele et al., 2016).
The %HRmax was calculated based on the maximum values reached in
maximum aerobic testing. The training load was measured from all last
sessions of each of the program's three phases from which the HRV data
was collected. The RPE data were assessed 10 min after the end session.
2.5. Statistical analysis
Data collected are presented by descriptive statistics (mean and
standard deviation). The normality was checked by Shapiro–Wilk test.
Data were skewed, a natural logarithmic transformation was performed
on the RMSSD and LF/HF for parametric analysis. After this, the One-
way analysis of variance (ANOVA) for repeated measurements was con-
ducted with a Sidak post hoc adjustment to compare the measures over
the time of sessions (pre-exercise × recovery) for all HRV indices
(lnRMSSD, LFn.u, HFn.u, and lnLF/HF) and the training load variables.
The Mauchly test was performed to analyze the sphericity of the data,
being adjusted through the correction of Greenhouse-Geisser in cases of
sphericity violation. Additional statistical analyses were performed us-
ing paired t-tests to compare characteristics of participants pre and
post-training programs. The level of significance was set at 5%
(p(xxxx) 1–10 5
3. Results
The study included all volunteers who completed the training proto-
col and maintained an adherence of above 85% based on a previous
study about kettlebell training in young women (Rufo-Tavares et al.,
2020). Twenty-nine women attended the anamnesis session at the first
moment. Nine volunteers were excluded, being the three factors for
obesity, incompatibility of time for training, and level of physical activ-
ity. Another 6 participants have dropped out for unreported personal
reasons. Of the 20 participants selected, three were unable to attend the
training and 1 exceeded the number of absences (>15%), totaling four
exclusions. Sixteen volunteers have completed the training program;
however, one participant met one of the exclusion criteria (participa-
tion in another routine exercise) and 5 participants presented low-
quality data (artifacts in the RR series). Therefore, 10 participants were
included in the final analysis (Fig. 3). For this sample, the statistical
power found was 80% (effect size f: 0.4 - equivalent to a large Cohen's d
found in the present study for O2; alpha: 5%), calculated by G*Power
3.1. The participant's characteristics are detailed in Table 1.
3.1. Training load
The one-way ANOVA repeated measures revealed a significant main
effect of phases from total volume (TV) during the three sessions
(p 0.05), except for lnRMSSD (Fig. 6A). The lnRMSSD indice re-
mained depressed until 30 min of the recovery period (pof kettlebell protocols to
promote improved physical fitness.
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Upon cessation of exercise, vagal activity is reactivated and with-
drawal of sympathetic activity occurs, progressively increasing HRV
(Peçanha et al., 2014). Thus, parasympathetic activity gradually re-
sumes predominance in cardiac modulation in a coordinated manner.
Studies applying HIIT protocols (treadmill and bicycle) with intensities
between 85 and 97%HRmax have shown that the reduction in HRV can
persist up to 24 h after cessation of exercise (Burma et al., 2020; Schaun
and Del Vecchio 2018; Cipryan et al., 2016; Kaikkonen et al., 2008;
Buchheit et al., 2007; Niewiadomski et al., 2007; Seiler et al., 2007;
Furlan et al., 1993). In this study, the same behavior was observed up to
30 min post-exercise in the first two phases of the program (between
the 3rd and 8th week).The parasympathetic indices lnRMSSD and HFnu
(Araújo et al., 2020; Dupuy et al., 2012) demonstrated a reduction con-
cerning the pre-exercise values and, conversely, the indices LFnu and
lnLF/HF (sympathetic predominance) (Task Force 1996) increased sig-
nificantly.
The complete resumption of parasympathetic activity is known to
occur after the conclusion of the sympathetic clearance, i.e., reduction
of stimulus to the sympathetic pathway through the metaborreflex (i.e.,
reducing muscle acidosis and removing blood lactate) (Hoshi et al.,
2017). The short-term restoration (60–90 min) of HRV indices seems to
be influenced by some factors, such as the intensity (Hoshi et al., 2017;
Michael et al., 2017b; Stanley et al., 2013). High-intensity exercise ses-
sions are associated with a more significant imbalance of the sympatho-
vagal relationship in the post-exercise period, with delayed resetting of
HRV indices (Casonatto et al., 2011; Gladwell et al., 2010; Buchheit et
al., 2007; Parekh and Lee 2005).
Similarly, the literature indicates that a 12-min high-intensity ket-
tlebell session (30:30s work-to-rest ratio) between 80 and 90% of pre-
dicted HRmax and controlled pace (15 swings each series) reduced the
indices HF and RMSSD (∼40%) and significantly increased the indices
LF and LF/HF (∼40 and ∼50%, respectively) up to 30 min of recovery
(Wong et al., 2017). These findings support this study when considering
the first two phases of the program. In this case, 30 min does not seem
to be enough for complete recovery of HRV.
Furthermore, another factor influencing the late resumption of HRV
is the kind of exercise employed. Similar protocols to those used in ket-
tlebell training (i.e., composed of whole-body exercises) demonstrate
sympathetic overactivity for a longer time than more traditional proto-
cols when evaluating short-term recovery (Kliszczewicz et al., 2016).
Kliszczewicz et al. (2016) in comparison a traditional treadmill running
session (continuous aerobic) (∼93%HRmax) with a whole-body exer-
cise protocol ("Cindy" - CrossFit®) (∼95%FCmax), both lasting 20 min,
observed that parasympathetic indices (RMSSD and HF) had a more ex-
pressive reduction until 60 min post whole body exercise session.
On the other hand, Schaun and Del Vecchio (2018), by applying two
HIIT protocols (Tabata et al., 1997) –one on the cycle ergometer
(88%HRpeak) (8x20:10s at 170%Pmax) and another of bodyweight ex-
ercises (87%HRpeak) (8x20:10s all-out), found a similarity in the reduc-
tion of HRV (high parasympathetic inhibition) and recovery from both
subsequent sessions when autonomic activity was assessed after 24 h.
In this case, the literature shows isolated high-intensity training ses-
sions involving whole-body exercises, and autonomic recovery can be
achieved within 1–24 h (Kliszczewicz et al., 2016, 2018; Schaun and
Del Vecchio 2018).
This study corroborates the literature about the delayed recovery of
parasympathetic indices and sympathetic hyperactivity after sessions in
the early phases of high-intensity kettlebell training (phases I and II).
However, this research differs when evaluating the autonomic response
throughout a training program with individualized load progression.
This fact may explain the distinct response presented in the last training
phase. Return to pre-exercise values of the frequency domain indices
was observed at 20 min of recovery in the program's third phase. The
reduction in sympathetic activity seems to reflect in the indices lnLF
and lnLF/HF values, which showed a return, in parallel with the HFnu
indice (vagal activity), to pre-exercise values. Although the time do-
main response (lnRMSSD) did not return to the initial values, the auto-
nomic responses in the frequency domain allow us to view the recovery
of vagal activity and sympathetic withdrawal within 30 min in the last
phase of the program.
The third phase of high-intensity kettlebell training is characterized
by higher volume (TV) and intensity (kettlebell weight - %BM) when
compared to the previous phases (I and II). Untrained people with
lower aerobic fitness tend to recover later vagal activity to basal levels
(Stanley et al., 2013; Gladwell et al., 2010). In this case, when observ-
ing the increased aerobic fitness (>10%) and the change in training
status (untrained to trained), one notices an adaptation of the auto-
nomic response since in Phase III, even with higher volume and inten-
sity employed, the recovery to pre-exercise levels occurs earlier than in
previous phases. In parallel, another measure that corroborates the
premise of an adaptation is found in the RPE values. Participants’ RPE
did not show any significant change throughout the training phases,
even with the increasing intensity of the sessions. Repeated exposure to
training can lead to adaptive responses associated with improved per-
formance (Borresen and Lambert 2008).
In this context, Yamamoto et al. (2001) demonstrated an increase in
the autonomic recovery response over six weeks of cycle-endurance
training with simultaneous improvement in aerobic fitness. In this
study, seven young men (21 ± 1 years) were submitted to sessions at
80% O2peak (4 d wk). In addition to the 12% increase in aerobic ca-
pacity, the lnLF/HF measured 20 min after exercise session were sig-
nificantly decreased and lnHF power increased, demonstrating im-
proved post-exercise recovery capacity.
It is known that 12-week HIIT programs between 85-95% HRmaxpeak
can promote adaptations in O2 and increase resting vagal activity
(Ramírez-Vélez et al., 2020; Boutcher et al., 2013). However, it
should be noted that, in this study, after ten weeks of training, there
were no increases in resting HRV measurements. According to
Yamamoto et al. (2001), the adaptations of the post-exercise recovery
response are achieved faster than the HRV responses at rest. In this
sense, study designs ≥12 weeks need to be developed to evaluate
adaptations in resting HRV.
In this study, it is essential to consider the following limitation: it
was not possible to perform a control session. Therefore, it is important
to consider assessing autonomic activity on a non-exercising day for fu-
ture studies.
5. Conclusions
After high-intensity kettlebell training sessions, the cardiac auto-
nomic modulation shows reduced HRV compared to pre-exercise val-
ues. The increased intensity does not impose an additional autonomic
overload throughout successive sessions and may even offer a faster re-
covery for most of the variability components studied. When the kettle-
bell load is prescribed according to individual progression criteria
(RPE, number of repetitions, and exercise performance techniques)
throughout training, the progressive increase in load did not impair car-
diac autonomic regulation.
CRediT authorship contribution statement
Sabrina P. Alves : Conceptualization, Methodology, Formal
analysis, Investigation, Writing – original draft. Carla Zimerer :
Conceptualization, Methodology, Investigation, Writing – review &
editing, Supervision. Richard D.Leite : Conceptualization, Re-
sources, Writing – review & editing. Letícia Nascimento Santos
Neves : Formal analysis, Writing – review & editing. Camila Mor-
eira : Investigation, Writing – review & editing. Luciana Carletti :
Conceptualization, Methodology, Formal analysis, Resources, Writ-
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S.P. Alves et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) 1–10 9
ing – review & editing, Supervision, Project administration, Fund-
ing acquisition.
Declaration of competing interest
None of the authors declares competing for financial interests.
Acknowledgment
We would like to thank the Coordination for Improvement of Higher
Education Personnel – CAPES, for their financial support, and all volun-
teers who participated in this study for their dedication.
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	Cardiac autonomic responses to high-intensity kettlebell training in untrained young women: A pilot study
	1. Introduction
	2. Material and methods
	2.1. Design
	2.2. Subjects
	2.3. Procedures
	2.3.1. Questionaries, physical activity, and resting blood pressure
	2.3.2. Anthropometry
	2.3.3. Maximum aerobic fitness
	2.3.4. Training program2.3.5. Autonomic modulation
	2.4. Training load
	2.5. Statistical analysis
	3. Results
	3.1. Training load
	3.2. Heart rate variability
	4. Discussion
	5. Conclusions
	
	Acknowledgment
	References
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