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Hayashi K et al. Recovery from Strenuous Downhill … Int J Sports Med
Physiology & Biochemistry Thieme
Introduction
Eccentric exercise causes muscle damage that is indicated by re-
ductions in muscular strength and range of motion of the joints, 
increases in muscular pain and soreness, and increased blood cre-
atine kinase activity and myoglobin concentration [1, 2]. Changes 
in such parameters related to muscle damage after eccentric exer-
cise are affected by age [3–6], sex [7, 8], and status of physical train-
ing [9]. There is a well-conceived notion that the recovery from 
strenuous exercise slows with age. Indeed studies using animal 
models have demonstrated that stretching of electrically-activat-
ed skeletal muscle to mimic eccentric muscle contractions of old 
mice results in a greater force decline and slower recovery of mus-
cle force than in young mice [1, 3]. Similarly, in human studies using 
sedentary adults, increasing age has been associated with a slower 
rate of recovery of muscular force [5, 10] and damages [11] from a 
series of eccentric contractions. However, the process of aging is 
often confounded by coexisting diseases and gradual sedentary 
lifestyles that progress with advancing aging. Accordingly, aging 
is difficult to be isolated from these epiphenomenon of aging. Cur-
rently, it is unclear whether older adults who are apparently healthy 
and habitually exercising demonstrate slower rates of recovery 
from unaccustomed eccentric exercise. In a small-scale study, rec-
reationally-active middle-aged adults did not display a slower re-
covery from unaccustomed eccentric exercise of the elbow flexors 
than younger adults [12]. In addition, recreationally resistance-
trained young and middle-aged adults also showed a similar pat-
tern of recovery as assessed by markers of muscle damage follow-
ing high-volume resistance exercise [13].
Hayashi Koichiro et al. Recovery from Strenuous Down- hill … Int J Sports Med 2019; 00: 00–00
Recovery from Strenuous Downhill Running in Young and Older 
Physically Active Adults
 
Authors
Koichiro Hayashi1, 2, Miriam E. Leary1, Stephen J. Roy1, Jitanan Laosiripisan1, Evan P. Pasha1, Hirofumi Tanaka1
Affiliations
1 Cardiovascular Aging Research Lab, Department of 
Kinesiology and Health Education, The University of 
Texas at Austin, Austin, United States
2 Department of Human Development, Kokugakuin 
University, Yokohama, Japan
Key words
muscle damage, aging, exercise
accepted 28.05.2019
Bibliography
DOI https://doi.org/10.1055/a-0951-0017
Published online:2019
Int J Sports Med 
© Georg Thieme Verlag KG Stuttgart · New York 
ISSN 0172-4622
Correspondence
Dr. Koichiro Hayashi, Ph.D.
Department of Human Development, 
Kokugakuin University, 
3–22–1 Shin-Ishikawa,
225–0003 Yokohama,
Japan 
Tel.: + 81/45/904 7658, Fax: + 81/45/904 7658 
k-hayashi@kokugakuin.ac.jp
AbSTR AcT
There is a well-conceived notion that rate of recovery from 
strenuous exercise gets slower with age. However, it is unclear 
whether older adults who exercise habitually demonstrate 
slower rates of recovery. We determined whether older adults 
who are physically active demonstrate slower rates of recovery 
from unaccustomed strenuous exercise compared with young-
er peers. Healthy young sedentary (n = 10, 28 ± 2 years), young 
endurance-trained (n = 15, 27 ± 2 years), and older endurance-
trained (n = 14, 58 ± 2 years) men and women were studied. 
Participants performed 45 min of downhill running at 65 % of 
their maximal oxygen consumption. Visual analog pain scores 
of muscle groups increased at 24, 48, and 72 h in all three 
groups (p < 0.05), and changes in the muscular pain scale of the 
legs was smaller in the older trained group than in the young 
trained group. Maximum isometric strengths at 90 ° decreased 
in all groups at 24 h, but the recovery rates were not different 
at 72 h among the groups. Plasma creatine kinase activity and 
myoglobin concentration increased at 24 h following downhill 
running and returned to baseline at 48 h in both the young and 
older trained groups. The present findings are not consistent 
with the prevailing notion that older trained adults have a 
slower rate of recovery from strenuous exercise.
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mailto:k-hayashi@kokugakuin.ac.jp
Hayashi K et al. Recovery from Strenuous Downhill … Int J Sports Med
Physiology & Biochemistry Thieme
Among various protocols to implement strenuous exercise, 
downhill running on a treadmill has been well established as a valid 
and reliable exercise modality to induce delayed onset muscle sore-
ness (DOMS) [14]. Additionally, downhill running is a more general-
izable form of unaccustomed exercise and causes a greater degree of 
DOMS than level running due to the skeletal muscle involved absorb-
ing more force than it produces [15] and a greater proportion of dis-
rupted muscle fibers [16]. Most previous studies in this area [5, 10–12] 
have used localized eccentric muscle contractions to induce DOMS 
in adults varying in age. However, localized eccentric muscle contrac-
tions are experimental conditions created in the laboratory setting 
and may not be translated to practice settings of popularly-practiced 
physical activity and sports. No previous study has addressed the 
rate of recovery in young and older exercise-trained adults using this 
effective and generalizable form of exercise.
With this information as background, the aim of the present 
study was to test the hypothesis that older adults who are healthy 
and physically active would demonstrate slower rates of recovery 
from unaccustomed strenuous exercise of downhill running than 
younger peers.
Materials and Methods
Participants
A total of 39 healthy men and women were studied. They were di-
vided into three groups according to their age and physical activ-
ity status; the young sedentary group (men; n = 6, women; n = 4), 
the young exercise-trained group (men; n = 10, women; n = 5), and 
the older exercise-trained group (men; n = 8, women; n = 6). Young 
and older groups were 19–39 and 50–77 years of age, respective-
ly. Participants in the trained groups had been performing regular 
aerobic exercise (primarily running) at least twice or more a week 
for at least two years. Average weekly frequencies of strenuous en-
durance exercise were 4.4 ± 0.5 days/week in the young trained and 
4.0 ± 0.6 days/week in the older trained groups, and were not dif-
ferent between the groups. The participants in the sedentary group 
had not engaged in a regular exercise program for at least one year. 
Older sedentary participants were not included in the present study 
due to safety concerns associated with downhill running. All par-
ticipants were nonsmokers and were free of overt chronic diseases 
as assessed using medical history and any physical limitations. All 
older women were postmenopausal. Three women in the young 
groups were using oral contraceptives, and other premenopausal 
women had been experiencing regular menstrual cycles. In pre-
menopausal women who did not use oral contraceptives, all meas-
urements were conducted in early follicular phase of their men-
strual cycle, because the phase contains the lowest estrogen lev-
els. All participants gave their written informed consent prior to 
study participation, and the ethics committee of the University of 
Texas at Austin approved all procedures. We confirmed that the 
present study meets the ethical standards of the Journal[17].
Procedures
Participants visited the laboratory on five separate occasions. On 
the first visit, participants filled out the standard health research 
questionnaire. They then underwent a familiarization/measure-
ment session. The familiarization portion was used to introduce the 
participants to actual downhill running on treadmill. Then each 
participant’s maximal oxygen consumption (V̇O2max) were meas-
uredusing a maximum exercise test. On the second visit, the par-
ticipants underwent the baseline measurements, including anthro-
pometry, body composition, markers of muscle damage (plasma 
creatine kinase activity and myoglobin concentration, visual analog 
scale of pain and soreness, and joint range of motion) and maxi-
mum isometric muscular strength of their leg. Following the base-
line measurements, participants performed downhill running. After 
the downhill running protocol, various markers of muscle damage 
and muscular strength were obtained 24 h post (the third visit), 
48 h post (the forth visit) and 72 h post (the fifth visit). There were 
at least 3 days between the first and second visits, with no more 
than 7 days between the two visits. Participants were instructed to 
fast at least 3 h and to avoid any strenuous exercise for the 48 h be-
fore the measurements. Participants were asked to keep their reg-
ular diet throughout the testing sessions.
In the present study, we focused on the impact of downhill run-
ning on muscle damage to quadriceps, because previous observa-
tions showed that the largest muscle damage by downhill running 
was observed in knee extensors [18].
Maximal oxygen consumption
Maximal oxygen consumption (V̇O2max) was measured with an in-
cremental treadmill protocol test as previously described [19]. 
After a 5-min warm-up period, the subject ran at a speed that cor-
responded to 70–80 % of age-predicted maximal heart rate [20]. 
Treadmill speed remained constant throughout the test, while the 
grade was increased by 2 % every 2 min until volitional exhaustion. 
A mouthpiece and heart rate monitor (Polar Electro Inc, Lake Suc-
cess, NY) were worn to collect expired air and obtain heart rate. The 
original Borg’s rating of perceived exertion (RPE) scale was obtained 
every minute. A metabolic cart (MAX-1, Physio-Dyne, Quogue, NY) 
was used to measure flow and gas composition from expired air 
collected by the mouthpiece. At least two of the following three 
criteria were met by each subject: 1) a plateau in oxygen uptake 
with increasing exercise intensity, 2) a respiratory exchange 
ratio ≥ 1.1, and 3) achievement of age-predicted maximal heart 
rate [20]. V̇O2max was determined by the highest values of oxygen 
uptake that were sampled every 20 s. The V̇O2max values were used 
to set the speed of treadmill during the downhill running.
Downhill running
Participants performed downhill running at − 16 % of slope and at 
a treadmill speed that corresponded with 65 % of their V̇O2max [21]. 
Participants warmed up on treadmill on a level grade at the same 
speed as downhill running for 5 min. Following the warming up pe-
riod, participants began downhill running. The downhill protocol 
consisted of three 15-minute sessions with 5-minute rest intervals 
in seated position. Heart rate (using Polar heart rate monitor), and 
RPE (for cardiorespiratory and lower limbs, separately) were record-
ed every 5 min. Similar protocols have been successfully utilized to 
induce DOMS in young and older adults [14, 22].
Anthropometric assessment
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Hayashi K et al. Recovery from Strenuous Downhill … Int J Sports Med
Height ( ± 0.1 cm) and body weight ( ± 0.1 kg) were measured using 
a physician’s balance scale. Body composition was assessed using 
the 7-site skinfold thickness technique [23, 24].
Joint range of motions
A goniometer was used to assess the active range of motions of 
knee (extension) and hip (extension and flexion) joints as indices 
of muscle stiffness. Each measurement was repeated twice and av-
eraged for both left and right sides. The sites of goniometer were 
marked with a semi-permanent-ink pen to ensure good day-to-day 
repeatability. Hip flexion was tested while the subject was placed 
in the supine position with their knees bent over the edge of the 
treatment table. The subject was instructed to flex the knee to the 
chest, and hip flexion angle was assessed. The stationary arm of the 
goniometer was placed along the lateral midline of the pelvis; the 
axis of movement placed at the lateral aspect of hip aligned with 
the greater trochanter, and the moving arm was placed along the 
lateral midline of the femoral lateral condyle. Hip extension was as-
sessed while the subject was placed in the prone position. While 
the pelvis is stabilized, the subject raised their leg off the table. The 
stationary arm of the goniometer was aligned the lateral midline 
of the pelvis; the axis of movement was placed on the lateral aspect 
of the hip aligned with the greater trochanter and the moving arm 
placed along the lateral midline of the femur aligned with the fem-
oral lateral condyle.
Knee extension was measured with the subject laying supine, 
with both knee and hip flexed. The opposite leg lay flat on the table 
throughout the examination. The subject actively extended the 
knee through the full range of motion until resistance was felt, 
while the hip was maintained at 90 ° flexion. The stationary arm of 
the goniometer was aligned along the femoral greater trochanter; 
the axis of movement placed at the lateral femoral condyle at the 
knee joint and the moving arm aligned with the lateral malleolus.
Visual analog pain scale
A validated visual pain scale (VAS) was used to determine the level 
of muscle soreness [25]. The scale was on a 10-point scale (0 being 
absence of soreness, 10 being worst imaginable soreness). Partic-
ipants were asked to rate the VAS at their quadriceps, calves, and 
glutes during walking in daily life. In addition, VAS of subject’s legs 
was obtained when angles of hip flexion (VAS-hip flexion), hip ex-
tension (VAS-hip extension), and knee extension (VAS-knee exten-
sion) were measured.
Maximum muscular strength
Maximum voluntary isometric forces of the dominant knee exten-
sors were measured using the isokinetic dynamometry system 
(Cybex II, Cybex, Inc, Ronkonkoma, NY). Participants were seated 
on the isokinetic machine, fixed by belts for waist, shoulders, and 
thigh. Maximum isometric muscular strength was measured by de-
termining peak torque during knee extension contractions at 45 ° 
and 90 ° of knee angles. Participants performed three maximum 
knee extension contraction each for knee angles with 60-second 
rests between trials. The average peak torque of the three trials was 
used for further analyses.
Blood samples
Blood samples (5 ml) were drawn from the antecubital vein by a 
certified phlebotomist. Plasma was separated by centrifugation for 
15 min. All plasma samples stored at − 80 °C for biochemical anal-
yses at a later date. Creatine kinase activity and myoglobin concen-
tration, as indices of muscle damage, were analyzed using com-
mercially available ELISA assay kits (Creatine kinase; POINTE SCI-
ENTIFIC #OC922–300, Myoglobin; CALBIOTECH #MG017C). Due 
to the budget constraints, these measurements were measured 
only in the older trained and young trained groups.
Statistical analyses
Changes in dependent variables of muscular damages over time 
were compared among three groups by a two-way ANOVA with re-
peated measures (time × groups). In the subgroup analyses that 
we conducted, we did not observe significant sex differences in 
any parameters following downhill running. Thus, the data of male 
and female participants were combined and analyzed together. 
Scheffe’s post-hoc analyses were performed when significance was 
achieved. Pearson correlation coefficient were used for correlation 
analyses between variables of interest. P-values less than 0.05 were 
considered significant. Numeric data are expressed as means ± SEM 
as the overall sample sizes are relatively small in the present study. 
All statistical analyses were performed using StatView software 
(5.0; SAS Institute, Tokyo, Japan).
Results
Selected participant characteristics
Participants’ anthropometric characteristicsand V̇O2max are shown 
in ▶Table 1. Height, body weight, and BMI did not differ among 
the three groups. Percent body fat was greater in the older trained 
group than in the young trained group (p < 0.05). V̇O2max in the 
young trained group was higher than those in the young sedentary 
and older trained groups (p < 0.05).
Downhill running
Relative exercise intensity as measured by relative heart rate, RPEs 
for cardiorespiratory function and lower legs, and treadmill speeds 
during the downhill running shown in ▶Table 2. Relative heart rate 
and RPE for cardiorespiratory function did not differ between the 
three groups at any time during the downhill running. RPE for lower 
limbs in the older trained group were significantly lower than those 
in the young groups at 30-minute during the downhill running.
Range of motion
In ▶Table 3, changes in ranges of motion of knee and hip joints are 
shown. Before downhill running, there were no significant differences 
in knee and hip range of motion among the three groups. The range 
of motion for knee extension did not change in the older trained and 
the young sedentary group. In the young trained group, the range of 
motion for knee extension decreased at 24 hour. The range of motion 
for hip flexion decreased significantly after downhill running in the 
young trained group, but did not decrease in the young sedentary and 
the older trained group. The range of motion for hip extension de-
creased significantly after downhill running in the young sedentary 
group but not in the young trained and the older trained groups.
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Hayashi K et al. Recovery from Strenuous Downhill … Int J Sports Med
Physiology & Biochemistry Thieme
Pain scale
Changes in pain scales of quadriceps, calf, and glutes are shown in 
▶Table 4. No significant group × time interaction effects were ob-
served for each pain scale. A significant main effect for time in each 
muscle was observed in all groups combined. Pain scores of quadri-
ceps and calves were greater at 24, 48 and 72 hour than baseline in 
all three groups (p < 0.05). Pain scores of glutes were greater at 24 
and 48 hour than baseline in all three groups (p < 0.05).
Pain scales of legs during knee extension, hip flexion and hip ex-
tension are shown in ▶Fig. 1. In the young sedentary and young 
trained groups, pain scale during knee extension increased signifi-
cantly at 24 and 48 h. In contrast, the pain scale was elevated mild-
ly only at 48 h in the older trained group. The pain scale during hip 
flexion increased significantly at 24 h in the young sedentary and 
trained groups. However, the pain scale did not change in the older 
trained group. The pain scales during hip extension increased sig-
nificantly at 24 h in all three groups.
Muscular strength
Mean muscular strength (peak torque) during isometric knee ex-
tension at 45 ° (Young Sedentary; 93 ± 9, Young Trained; 108 ± 9, 
Older Trained; 97 ± 9 Nm) and 90 ° (Young Sedentary; 139 ± 21, 
▶Table 1 Selected characteristics of the subjects.
Young Sedentary Young Trained Older Trained ANOVA P-value
N 10 15 14
Sex, M/F 6/4 10/5 8/6
Age, yrs 27.5 ± 2.2 26.8 ± 1.8 57.5 ± 2.3*† P < 0.05
Height, cm 169.5 ± 3.3 173.9 ± 1.3 171.4 ± 1.4 N.S.
Body weight, kg 64.4 ± 5.6 70.8 ± 3.0 72.9 ± 4.3 N.S.
BMI, kg/m2 22.1 ± 1.1 23.3 ± 0.9 24.6 ± 1.2 N.S.
Body fat, % 20.4 ± 1.7 17.7 ± 1.1 22.6 ± 4.5† P < 0.05
V̇O2max, ml/kg/min 39.9 ± 1.6 51.4 ± 1.4* 40.8 ± 3.2† P < 0.05
Data are expressed as Means ± SEM: BMI = Body mass index, V̇O2max = Maximum oxygen uptake: * P < 0.05 vs. Young Sedentary Group, † p < 0.05 vs. 
Young Trained Group.
▶Table 2 Exercise intensity and PRE and running speeds during downhill running.
Young Sedentary Young Trained Older Trained
Relative HRmax, % 15 min 71.3 ± 1.6 66.5 ± 2.7 63.7 ± 2.4
30 min 77.2 ± 2.1 70.1 ± 2.9 67.6 ± 1.9
45 min 77.2 ± 2.1 72.1 ± 2.9 69.7 ± 1.9
RPE cardiorespiratory 15 min 10.2 ± 0.8 9.6 ± 0.7 8.0 ± 0.4
30 min 11.6 ± 0.8 10.2 ± 0.8 8.9 ± 0.7
45 min 12.2 ± 0.9 10.7 ± 0.9 9.7 ± 0.9
RPE lower limbs 15 min 12.3 ± 0.8 11.6 ± 1.0 10.3 ± 0.6
30 min 14.9 ± 0.7 13.6 ± 0.6 11.1 ± 0.6** 
45 min 16.0 ± 0.9 14.3 ± 0.9 12.3 ± 0.7* 
Running speed, km·h − 1 6.8 ± 0.3 9.0 ± 0.3** 6.9 ± 0.6
Data are expressed as Means ± SEM: HRmax = heart rate maximum, RPE = rating perceived exhaustion: * p < 0.05 vs. Young Sedentary Group, 
 ** P < 0.05 vs. other two groups.
▶Table 3 Range of motion of knee and hip joints at baseline and following downhill running.
baseline 24 h 48 h 72 h Interaction effects
Knee extension, degree Young Sedentary 103 ± 4 99 ± 4 101 ± 4 101 ± 4 N.S.
Young Trained 107 ± 3 103 ± 3* 104 ± 3 107 ± 3
Older Trained 104 ± 3 101 ± 3 101 ± 3 101 ± 3
Hip flexion, degree Young Sedentary 108 ± 4 106 ± 4 106 ± 5 105 ± 4 P < 0.05
Young Trained 102 ± 3 97 ± 3* 100 ± 2 102 ± 2
Older Trained 100 ± 2 100 ± 3 103 ± 3 103 ± 2
Hip extension, degree Young Sedentary 22 ± 2 17 ± 2* 18 ± 1* 17 ± 1* P < 0.05
Young Trained 20 ± 1 18 ± 1 18 ± 1 20 ± 1
Older Trained 19 ± 1 18 ± 2 20 ± 2 20 ± 2
Data are expressed as Means ± SEM: * P < 0.05 vs. Baseline within the same group.
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Hayashi K et al. Recovery from Strenuous Downhill … Int J Sports Med
Young Trained; 156 ± 10, Older Trained; 119 ± 13 Nm) did not differ 
among the three groups at baseline (▶Fig. 2). Two-way ANOVA 
have revealed that the pattern of the changes in muscular strength 
during isometric knee extension at 45 ° and 90 ° did not differ 
among the three groups (P values for interaction = 0.35 and 0.91, 
respectively). Isometric strength during knee extension at 45 ° did 
not decrease significantly in the young trained group, but the 
strength decreased at 24 h significantly in the other two groups. 
Isometric strength during knee extension at 90 ° decreased signif-
icantly at 24 h in all groups. In young sedentary and older trained 
groups, the strength at 48 h remained lower than baseline values.
There were no significant relationships between age and de-
clines in muscular strength after downhill running (r = 0.08~0.30, 
p = 0.67~0.11). There were no significant associations between 
baseline muscular strength during knee extension (at 90 °and 45 °of 
knee angles) and magnitudes of pain or decreases in range of mo-
tion during knee extension or muscle strength after downhill run-
ning. However, there was a significant negative correlation between 
age and increases in pain scale during knee extension (r = − 0.44, 
p < 0.05).
Blood samples
Changes in plasma creatine kinase activity and myoglobin concen-
tration are shown in ▶Fig. 3. Two-way ANOVA revealed no signifi-
cant group x time interaction effects for changes in creatine kinase 
activity and myoglobin concentration. Plasma creatine kinase ac-
tivity and myoglobin concentration increased significantly at 24 h 
and returned to baseline at 48 h in both the young and older trained 
groups.
Rates of recovery of muscle damage
We calculated the slopes or rates of recovery between 24 h and 72 h 
in pain scales, isometric muscular strengths, and range of motions. 
There were no significant differences in the slope of these param-
eters among the three groups except for the slope of pain scale 
during knee extension to be smallest in older trained group 
(p < 0.05).
Discussion
In the present study, we determined whether older adults who are 
healthy and engage habitually in regular exercise would demon-
strate slower rates of recovery than younger peers from the unac-
customed exercise of downhill running. The rates of recovery of 
muscular strength, range of motion, plasma creatine kinase activ-
ity and myoglobin concentration following downhill running were 
not affected by age. Interestingly, changes in levels of muscular 
pain of the legs duringknee extension and hip flexion were signifi-
cantly smaller in the older trained group than in their young peers. 
These results indicate that recovery rates from downhill running 
are not influenced by age in habitually exercising adults, proving 
inconsistent with the prevailing notion that recovery rates get slow-
er as one gets older.
Muscle mass and strength decline gradually with advancing age, 
and satellite cells, major players in repairing muscle damage, de-
crease in number gradually and progressively with advancing age 
[26, 27]. Accordingly, musculoskeletal tissues in older adults are 
thought to be more susceptible to injury [28]. Indeed, in animal 
studies, recovery from electrically-induced muscular damage was 
slower in old vs. young rodents [1, 3]. It is difficult, however, to ex-
trapolate the results of manually-induced forced muscle damage 
in animal models to those induced by voluntary exercise in exercis-
ing humans. In fact, the available studies in humans are highly con-
troversial with some studies reporting an age-related slower recov-
ery from exercise [5, 10, 11] while others report no age-associated 
differences [4, 12, 13]. We reasoned that the exercise training sta-
tus and/or health status of study participants may have contribut-
ed to these contradictory results as the influence of aging is often 
compounded by the concomitant sedentary lifestyles and coexist-
ing cardiovascular and other degenerative diseases. These factors 
are often difficult to tease out from the influence of aging per se. 
Considering the fact that there has been a marked increase in the 
number of masters athletes in recent years [29], the investigation 
of the recovery rates in older exercise-trained adults would be time-
ly. In the present study, we compared recovery rates from strenu-
ous downhill running in apparently healthy young and older exer-
cise-trained adults. There were no significant age-related differ-
ences in the recovery from strenuous exercises in the present study.
These results were consistent with the results of previous stud-
ies conducted in recreationally active [4, 12] and resistance-trained 
individuals [13]. Previous studies in masters athletes, including en-
▶Table 4 Pain scale values at baseline and following downhill running.
baseline 24 h 48 h 72 h Interaction 
effects
Pain Quadriceps, points Young Sedentary 0.1 ± 0.1 4.7 ± 0.6* 4.9 ± 0.7* 3.2 ± 0.8* N.S.
Young Trained 0.2 ± 0.1 3.7 ± 0.5* 4.2 ± 0.6* 2.7 ± 0.5* 
Older Trained 0.0 ± 0.0 2.4 ± 0.6* 2.7 ± 0.6* 1.5 ± 0.4* 
Pain Calves, points Young Sedentary 0.1 ± 0.1 4.1 ± 0.9* 5.0 ± 1.1* 3.2 ± 0.9* N.S.
Young Trained 0.1 ± 0.1 3.3 ± 0.6* 3.9 ± 0.7* 2.2 ± 0.5* 
Older Trained 0.0 ± 0.0 2.3 ± 0.5* 4.1 ± 0.8* 2.1 ± 0.6* 
Pain Glutes, points Young Sedentary 0.1 ± 0.1 3.6 ± 0.7* 2.6 ± 0.6* 1.5 ± 0.7 N.S.
Young Trained 0.1 ± 0.1 3.1 ± 0.5* 2.6 ± 0.6* 1.4 ± 0.5
Older Trained 0.1 ± 0.1 2.9 ± 0.6* 2.8 ± 0.5* 1.0 ± 0.3
Data are expressed as Means ± SEM: * P < 0.05 vs. Baseline within the same group.
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Hayashi K et al. Recovery from Strenuous Downhill … Int J Sports Med
Physiology & Biochemistry Thieme
durance runners [30] and cyclists [31, 32], have also reported that 
recovery of muscular voluntary contraction was not different be-
tween masters athletes and young athletes. In one study that re-
ported a slower recovery of maximal voluntary contractions after 
55 km trail run, close examination of the data indicates that the 
pattern of recovery was very similar between young and older ath-
letes [33]. Aforementioned studies reporting slower recovery of 
muscular damage after eccentric exercise in older vs. young adults 
were conducted in sedentary individuals as participants [5, 10, 11]. 
Taken together, these results do not support the notion that older 
exercise-trained adults demonstrate a slower recovery from eccen-
tric exercise.
Increased blood creatine kinase and myoglobin concentrations 
indicate increased myocellular membrane permeability resulting 
from eccentric exercise-induced muscular damage. The effects of 
aging on blood markers of muscular damage following eccentric 
exercise remain controversial. In one study, inflammatory cytokine 
responses in human muscle and plasma creatine kinase activity 
after downhill running were smaller in the older male participants 
compared with those responses in young male participants [34]. 
In contrast, there were no differences in increase in the creatine ki-
nase activity and myoglobin concentration following eccentric ex-
ercise of elbow flexors between the young and middle-aged adults 
[12]. Additionally, plasma creatine kinase activities were not differ-
ent between young and older (masters) triathletes after three con-
secutive days of intense endurance training that included downhill 
running [35]. In the present study, plasma creatine kinase activity 
and myoglobin concentration were elevated at 24 h after the down-
hill running and returned gradually and similarly to the baseline 
values at 72 h after the exercise in both young and older trained 
participants. Collectively, these results suggest that the blood 
5
4
3
2
1
0
Baseline
Pa
in
 s
ca
le
s 
du
rin
g 
kn
ee
 e
xt
en
si
on
(p
oi
nt
s)
Group effect: p < 0.05
Time effect: p < 0.05
Interaction effects: p < 0.05
24 H
*
*
*
*
*
*
48 H 72 H
5
4
3
2
1
0
Pa
in
 s
ca
le
s 
du
rin
g 
hi
p 
fle
xi
on
(p
oi
nt
s)
Group effect: p < 0.05
Time effect: p < 0.05
Interaction effects: p < 0.05
* *
*
Baseline 24 H 48 H 72 H
5
4
3
2
1
0P
ai
n 
sc
al
es
 d
ur
in
g 
hi
p 
ex
te
ns
io
n
(p
oi
nt
s)
Group effect: p = 0.06
Time effect: p < 0.05
Interaction effects: p = 0.35
*
*
*
*
Baseline 24 H 48 H 72 H
Young Sedentary Young Trained Older Trained
▶Fig. 1 Pain scales of legs during knee extension, hip flexion and 
hip extension at baseline and following downhill running in the three 
groups.* P < 0.05 vs. Baseline within the same group.
10
5
0
– 5
– 10
– 15
– 20
10
5
0
– 5
– 10
– 15
– 20
Baseline
Ch
an
ge
s 
in
 M
ax
im
um
 Is
om
et
ric
 S
tr
en
gt
h
at
 9
0 
de
gr
ee
 (%
)
Ch
an
ge
s 
in
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ax
im
um
 Is
om
et
ric
 S
tr
en
gt
h
at
 4
5 
de
gr
ee
 (%
)
Group effect: p = 0.78
Time effect: p < 0.05
Interaction effects: p = 0.92
Group effect: p = 0.25
Time effect: p < 0.05
Interaction effects: p = 0.35
24 H
*
*
*
*
*
*
*
48 H 72 H
Baseline 24 H 48 H 72 H
Young Sedentary Young Trained Older Trained
▶Fig. 2 Maximum isometric muscular strength during knee exten-
sion at 45 ° and 90 ° degree at baseline and following downhill run-
ning in the three groups.* P < 0.05 vs. Baseline within the same 
group.
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Hayashi K et al. Recovery from Strenuous Downhill … Int J Sports Med
markers of recovery from muscle damage induced by eccentric ex-
ercise may not be associated with aging. Further studies are need-
ed to elucidate the impact of aging on muscle damage and inflam-
matory response induced by eccentric exercise.
In spite of the facts that strenuous exercise was performed at 
the same relative intensity and that objective biomarkers of mus-
cle soreness were similar among the groups studied, subjective 
pain scales were significantly lower in the older exercise-trained 
group than those of young groups, indicating that older adults may 
be less likely to express a greater pain scale after strenuous exer-
cise. The results of this study coincide with the previous studies 
comparing muscle soreness of middle-aged and young men fol-
lowing eccentric exercise of the elbow flexors [12, 36]. Pain percep-
tion associated with musculoskeletal conditions and pressure-re-
lated tenderness of cephalic muscle has been reported to decrease 
with advancing age[37, 38]. These results could explain the lower 
pain scales following downhill running in the older, exercise-trained 
group than in the young groups.
It has been reported that exercise training, in particular resist-
ance training, can enhance the rate of recovery of muscle damage 
following eccentric exercise [25, 39]. In the present study, howev-
er, we could not observe exercise training-related advantage for in 
muscular strength and range of motion of the knee joints after 
downhill running in young adults. The reason for this discrepancy 
may be that resistance-trained adults were assessed in the mode 
of resistance exercise in previous studies [25, 39] while exercise-
trained adults in the present study were evaluated in the unfamil-
iar mode of exercise (downhill running). Repeated bouts of the 
same unfamiliar exercises have been shown to considerably reduce 
the magnitude of muscle damage [16]. It will be interesting to de-
termine whether the time course and the magnitude of this re-
sponse/adaptation would be different between young and older 
exercise-trained adults.
One important limitation of the present study that should be 
emphasized is a lack of older sedentary participants. Accordingly, 
we cannot establish the influence of sedentary aging in the present 
study. This absence was due to safety concerns associated with 
downhill running. Secondly, we focused on the impact of downhill 
running on muscle damages involving quadriceps, gluteus maxi-
mus and biceps femoris. Therefore, we cannot clarify the effect of 
downhill running on other muscles (e. g., knee flexor and plantar 
flexor muscles). This selection was based on the previous observa-
tion that the largest muscle damage is often observed in knee ex-
tensors. In one previous study, for example, a decrease in maximum 
torque is substantially greater in knee extensors (14–17 %) than in 
plantar flexors (6–8 %) after downhill running [18].
In conclusion, we demonstrated that the rates of recovery from 
downhill running did not differ between young and older exercise-
trained adults. These findings are not consistent with the common-
ly-believed notion that aging increases the susceptibility of muscle 
damage and delays the recovery rate from exercise-induced mus-
cle damage.
Acknowledgements
Authors would like to thank Dr. Hsin-Fu Lin, Stephanie Lapierre and 
Brett Baker for their technical expertise and assistance.
Conflict of Interest
The authors declare no conflict of interest.
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