Rates of Recovery From Strenuous Exercise in Physically Active Older Adults
Phase: NA
Conditions: Muscles
Sponsor: University of Texas at Austin

Rate of Recovery from Strenuous Exercise in Physically Active Older Adults 
 
NCT02899650 
 
August 22, 2016 
 
 
 

Study Protocol 
Subjects.  A total of 39 healthy men and women were studied. They were 
divided into three groups according to their age and physical activity status; the young 
sedentary group, the young exercise-trained group, and the older exercise-trained 
group. Young and older groups were 19-39 and 50-77 years of age, respectively.  
Subjects in the trained groups had been performing regular aerobic exercise (primarily 
running) at least twice or more a week for at least two years. The subjects in the 
sedentary group had not participated in a regular exercise program for at least one year. 
Older sedentary subjects were not included in the present study due to safety concerns 
associated with downhill running. All subjects were nonsmokers. Subjects were free of 
overt chronic diseases as assessed using medical history. All subjects were free of 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 premenopausal women who did not use oral 
contraceptives, all measurements were conducted in early follicular phase of their 
menstrual cycle because the phase contains the lowest estrogen levels. All subjects 
gave their written informed consent prior to study participation, and the ethics committee 
of the University of Texas at Austin approved all procedures. 
Procedures. Subjects visited the laboratory on five separate occasions. On the 
first visit, subjects filled out the standard health research questionnaire. They then 
underwent a familiarization/measurement session. The familiarization portion was used 
to introduce the subjects to downhill running on treadmill. Then each subject’s maximal 
oxygen consumption (V
．
O2max) were measured using a maximum exercise test. On the 

second visit, the subjects underwent the baseline measurements, including 
anthropometry, body composition, markers of muscle damage (plasma concentrations 
of creatine kinase and myoglobin, visual analog scale of pain and soreness, and joint 
range of motion) and muscular strength of their leg (maximum isometric contraction). 
Following the measurements, subjects performed downhill running. After the downhill 
running protocol, various markers of muscle damage and muscular strength were 
obtained 24 hours post (the third visit), 48 hours post (the forth visit) and 72 hours 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. Subjects were instructed to fast at least 3 hour 
and to avoid any strenuous exercise for the 48 hours before the measurements. 
Subjects were asked to keep their regular diet throughout the testing sessions. 
Maximal oxygen consumption.  Maximal oxygen consumption (V
．
O2max) was 
measured with an incremental treadmill protocol test as previously described [32]. After 
a 5-min warm-up period, the subject ran at a speed that corresponded to 70–80% of 
age-predicted maximal heart rate [31]. Treadmill speed remained constant throughout 
the test, while the grade was increased by 2% every 2 minutes until volitional 
exhaustion. A mouthpiece and heart rate monitor (Polar Electro Inc, Lake Success, NY) 
were worn to collect expired gas and obtain heart rate. The rating of perceived exertion 
(RPE) scale was obtained every minute. A metabolic cart 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 [31]. V
．
O2max was determined by the highest values 

of oxygen uptake that were sampled every 20 s. The V
．
O2max values were used to set 
the speed of treadmill during the downhill running.  
Downhill running.  Subjects performed downhill running at -16% of slope at a 
speed that corresponded with 65% of their V
．
O2max [26]. Subjects warmed up on 
treadmill on a level grade at the same speed as downhill running for 5 min. Following 
the warming up period, subjects 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 recorded every 5 minutes. Similar protocols have been 
successfully utilized to induce DOMS in young and older adults [7,11,27].  
Anthropometric assessment.  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 [19,20] . 
Joint range of motions.  A goniometer was used to assess the range of 
motions of knee (extension) and hip (extension and flexion) joints as indices of muscle 
stiffness. Each measurement was repeated twice and averaged 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 assessed 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 femoral lateral 
condyle.  
Knee extension was measured with the subject laying supine, with both knee 
and hip flexed. The opposite leg lied 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 [9]. The scale was on a 10-point scale (0 being 
absence of soreness, 10 being worst imaginable soreness). Subjects 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 
extension (VAS-hip extension), and knee extension (VAS-knee extension) were 
measured. 
Muscular strength.  Maximum voluntary isometric forces of the dominant knee 
extensors were measured using the isokinetic dynamometry system (Cybex II, Cybex, 
Inc, Ronkonkoma, NY). Subjects were seated on the machine, fixed by belts for waist, 

shoulders, and thigh. Maximum isometric muscular strength was measured by 
determining peak torque during knee extension contractions at 90° and 45° of knee 
angles. Subjects 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 minutes. All 
plasma samples stored at -80°C until biochemical analyses at a later date. Creatine 
kinase activity and myoglobin concentration, as indices of muscle damage, were 
analyzed using commercially available ELISA assay kits. 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 repeated measures (time x groups). 
Scheffe’s post-hoc analyses were performed when significance was achieved. P-values 
less than 0.05 were considered significant. Numeric data are expressed as 
means±SEM. All statistical analyses were performed using StatView (5.0; SAS Institute, 
Tokyo, Japan) software.