Comparison of Physiological Variables Between the Elliptical Bicycle and Run Training in Experienced Runners.

Klein, IE, White, JB, and Rana, SR. Comparison of physiological variables between the elliptical bicycle and run training in experienced runners. J Strength Cond Res 30(11): 2998-3006, 2016-A novel outdoor elliptical bicycle (EBIKE) has been designed to elicit running-similar physiological adaptations while reducing the impact forces that commonly lead to injury. Various cross-training methods have been used to reduce injury risk, restore or maintain fitness, and prevent detraining. The purpose of this study was to compare 4 weeks of EBIKE-only training to run-only training on maximal oxygen consumption, ventilatory threshold, respiratory compensation point, running economy, and 5,000 m time trial times. Twelve experienced runners (age, 22.33 ± 3.33 years; running experience, 9.25 ± 4.53 years) completed 4 weeks of randomly assigned EBIKE or run training. Physiological and performance testing procedures were repeated, and subjects then performed a second matched 4-week training period in a crossover design. Ventilatory threshold was significantly greater after EBIKE (p ≤ 0.05; 41.60 ± 6.15 ml·kg·min) and run training (p ≤ 0.05; 42.33 ± 6.96 ml·kg·min) compared with the initial time point (40.17 ± 6.47 ml·kg·min). There were no significant group differences (p > 0.05) for these variables at any time point. In conclusion, EBIKE-only training yielded similar physiological and performance maintenance or improvements compared with run-only training. These results suggest that EBIKE training can be an effective cross-training method to maintain and improve certain physiological and performance variables in experienced runners over a 4-week period.

Using a practical approach for determining the most effective stretching strategy in female college division I volleyball players.

The purpose of this investigation was to quantify the effects that a practical bout of static stretching (SS) and dynamic stretching (DS) has on maximal countermovement jump (CMJ) height across a time spectrum of 25 minutes in National Collegiate Athletic Association Division I varsity volleyball players. Eleven female varsity volleyball players (mean ± SD; age 20.00 ± 1.55 years; height 1.78 ± 0.08 m; mass 74.55 ± 12.18 kg) volunteered for this investigation. Three days of randomized experimental testing (SS, DS, control) were completed. The SS protocol consisted of stretching 7 muscle groups. The DS protocol consisted of the volleyball team's actual DS routine of equal duration (30 seconds) to SS. Poststretch performance measures of CMJ were determined at 1, 5, 15, and 25 minutes poststretch. Countermovement jump had an acute significant trial-by-time interaction, indicating that DS was found to produce significantly higher scores than the SS and control session at 1 and 5 minutes poststretch, but not at 15 and 25 minutes poststretch. Additionally, there was a timing interaction within trials where SS scores were significantly lower at 1 minute poststretch compared with 5 and 25 minutes poststretch, and DS scores were significantly higher at 1 and 5 minutes poststretch compared with 15 and 25 minutes poststretch. Athletes engaging in competitive power sports should continue to utilize their DS routine but may need to do so within 5 minutes before activity.

METs and accelerometry of walking in older adults: standard versus measured energy cost.

PURPOSE: This study aimed to measure the metabolic cost (METs) of walking activities in older adults, to examine the relationship between accelerometer output and METs across walking activities, and to compare measured MET values in older adults with the MET values in the compendium. METHODS: Twenty older adults (mean age = 75, range = 60-90 yr) completed eight walking activities (five treadmill based, three free living) for 6 min each. Oxygen consumption (V˙O2) and resting metabolic rate (RMR) were measured using a portable metabolic system, and motion was recorded using a waist-mounted ActiGraph accelerometer (GT3X; ActiGraph, Pensicola, FL). Energy expenditure across activities was defined as kilocalories per minute and measured as METs (V˙O2 / RMR) and standard METs (V˙O2 / 3.5 mL·kg-1·min-1). Mixed modeling was used to assess differences in counts per minute and kilocalories per minute by weight status, sex, comorbidity status, and functional status. Linear regression analysis was applied to develop a prediction equation for kilocalories per minute. Energy costs of walking were subsequently compared with METs in the compendium of physical activities. RESULTS: Average measured RMR was 2.6 mL·kg-1·min-1, 31.6% less than the standard RMR of 3.5 mL·kg-1·min-1. On average, standard METs were 71% lower than the measured METs across all walking activities. Measured MET levels differed from previously reported values in the literature and values listed in the compendium, resulting in misclassification of activity intensities for 60% of the walking conditions. Average counts for the walking activities ranged from 809 (treadmill = 1.5 mph) to 4593 counts per minute (treadmill = 3.5 mph). Previous regression equations consistently overestimate all activities compared with the measured energy cost in this sample of older adults. CONCLUSION: This study identifies the need for equations and cut points specific to older adults.

Early-phase muscular adaptations in response to slow-speed versus traditional resistance-training regimens.

Thirty-four untrained women participated in a 6-week program to investigate slow-speed versus "normal" speed resistance-training protocols. Subjects were divided into: slow-speed (SS), normal-speed/traditional-strength (TS), normal-speed/traditional muscular endurance (TE), and non-exercising control (C) groups. Leg press, squats, and knee extensions were performed 2 days/week for the first week and 3 days/week for the remaining 5 weeks (~2 min rest). The SS group performed 6-10 repetitions maximum (6-10RM) for each set with 10 s concentric (con) and 4 s eccentric (ecc) contractions. The TS and TE groups performed sets of 6-10RM and 20-30RM, respectively, at "normal" speed (1-2 s/con and ecc contractions). TE and SS trained at the same relative intensity (~40-60% 1RM), whereas TS trained at ~80-85% 1RM. Pre- and post-training muscle biopsies were analyzed for fiber-type composition, cross-sectional area (CSA), and myosin heavy chain (MHC) content. The percentage of type IIX fibers decreased and IIAX increased in all three training groups. However, only TS showed an increase in percentage of type IIA fibers. CSA of fiber types I, IIA, and IIX increased in TS. In SS, only the CSA of IIA and IIX fibers increased. These changes were supported by MHC data. No significant changes for any parameters were found for the C group. In conclusion, slow-speed strength training induced a greater adaptive response compared to training with a similar resistance at "normal" speed. However, training with a higher intensity at "normal" speed resulted in the greatest overall muscle fiber response in each of the variables assessed.

Comparison of mechanomyographic sensors during incremental cycle ergometry for the quadriceps femoris.

The purpose of this study was to examine the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus power output relationships for the vastus lateralis and rectus femoris muscles during incremental cycle ergometry between the piezoelectric contact sensor (HP) and the accelerometer (ACC) sensor. Nine men performed an incremental cycle ergometry test to voluntary exhaustion. Polynomial regression analyses on a subject-by-subject basis indicated that the relationship between the normalized MMG amplitude versus normalized power output was best fit with either a linear, quadratic, or cubic model. These patterns were consistent between sensors for each muscle for each subject. No consistent relationship was found for MMG MPF within subjects and between muscle groups. In addition, there were no significant sensor x power output interactions for normalized MMG amplitude or MPF. These results suggest that, for cycle ergometry, the HP and ACC sensors provide similar information for the interpretation of motor control strategies during continuous exercise.

Physiological profile of women's Lacrosse players.

Increasing participation rates for women's lacrosse necessitate a clear understanding of fitness parameters for this athlete group. However, limited sport-specific information is available. We described the physiological profile of an NCAA Division I women's lacrosse team to provide current data for this specific athlete group. A descriptive analysis was used to assess physiologic variables. Twenty-four members (age 20.0 +/- 1.4 years, mass 64.7 +/- 9.6 kg, height 163.2 +/- 25.6 cm) of an NCAA Division I women's lacrosse team volunteered and provided consent. Fitness tests were conducted by the same researcher and were selected from standard physical fitness assessments. Tests included cardiovascular endurance (Bruce Protocol VO2max test and 1-mile run), flexibility (sit-and-reach test), muscular endurance (push-ups, sit-ups, and 60% of 1RM back squat), muscular strength (one-repetition maximum [1RM] back squat and 1RM bench press), body composition (BOD POD), muscle torque (quadriceps maximal voluntary isometric contraction), grip strength (hand dynamometer), vertical jump (Vertec vertical column), endurance strength (100- and 200-yard sprints), and Q-angle. Our results indicate that our sample of lacrosse players exhibited similar fitness characteristics to basketball, soccer, and track athletes. However, we found only average flexibility and a higher percentage of body fat, indicating possible areas for improvement in lacrosse training programs.

Comparison of early phase adaptations for traditional strength and endurance, and low velocity resistance training programs in college-aged women.

The purpose of this study was to investigate the effects of a six-week (16-17 training sessions) low velocity resistance training program (LV) on various performance measures as compared to a traditional strength (TS) and a traditional muscular endurance (TE) resistance training program. Thirty-four healthy adult females (21.1 +/- 2.7 y) were randomly divided into 4 groups: control (C), TS, TE, and LV. Workouts consisted of 3 exercises: leg press (LP), back squat (SQ), and knee extension (KE). Each subject was pre- and posttested for 1 repetition maximum (1RM), muscular endurance, maximal oxygen consumption (VO2max), muscular power, and body composition. After the pretesting, TS, TE, and LV groups attended a minimum of 16 out of 17 training sessions in which the LP, SQ, and KE were performed to fatigue for each of 3 sets. For each training session, TS trained at 6-10 RM and TE trained at 20-30 RM both with 1-2 second concentric/1-2 second eccentric; and LV trained at 6-10 RM, with 10 second concentric/4 s eccentric. Statistical significance was determined at an alpha level of 0.05. LV increased relative LP and KE 1 RM, but the percent increase was smaller than TS, and not different from C in the SQ. For muscular endurance, LV improved similarly to TE for LP and less than TS and TE for KE. Body composition improved for all groups including C (significant main effect). In conclusion, muscular strength improved with LV training however, TS showed a larger improvement. Muscular endurance improved with LV training, but not above what TE or TS demonstrated. For all other variables, there were no significant improvements for LV beyond what C demonstrated.

Physiological responses at five estimates of critical velocity.

The purpose of this study was to compare critical velocity (CV) estimates from five mathematical models, and to examine the oxygen uptake (VO(2)) and heart rate (HR) responses during treadmill runs at the five estimates of CV. Ten subjects (six males and four females) performed one incremental test to determine maximal oxygen consumption (VO(2max)) and four or five randomly ordered constant-velocity trials on a treadmill for the estimation of CV. Five mathematical models were used to estimate CV for each subject including two linear, two nonlinear, and an exponential model. Up to five randomly ordered runs to exhaustion were performed by each subject at treadmill velocities that corresponded to the five CV estimates, and VO(2) and HR responses were monitored throughout each trial. The 3-parameter, nonlinear (Non-3) model produced CV estimates that were significantly (P < 0.05) less than the other four models. During runs at CV estimates, five subjects did not complete 60 min at the their estimate from the Non-3 model, nine did not complete 60 min at their estimate from the Non-2 model, and no subjects completed 60 min at any estimate from the other three models. The mean HR value (179 +/- 18 beats min(-1), HR(peak)) at the end of runs at CV using the Non-3 model was significantly less than the maximal HR (195 +/- 7 beats min(-1), HR(max)) achieved during the incremental trial to exhaustion. However, mean HR(peak) values from runs at all other CV estimates were not significantly different from HR(max). Furthermore, data indicated that mean HR(peak) values increased during runs at CV estimates from the third minute to the end of exercise for all models, and that these increases in VO(2) (range = 367-458 ml min(-1)) were significantly greater than that typically associated with O(2) drift ( approximately 200 ml min(-1)) for all but the exponential model, indicating a VO(2) slow component associated with CV estimates from four of the five models. However, the mean VO(2) values at the end of exercise during the runs at CV estimates for all five mathematical models were significantly less than the mean VO(2max) value. These results suggest that, in most cases, CV estimated from the five models does not represent a fatigueless task. In addition, the mean CV estimates from the five models varied by 18%, and four of the five mean CV estimates were within the heavy exercise domain. Therefore, CV would not represent the demarcation point between heavy and severe exercise domains.

Effect of the Wingate test on mechanomyography and electromyography.

The purpose of this investigation was to examine mechanomyographic (MMG) and electromyographic (EMG) amplitude responses of the superficial quadriceps femoris muscles during the Wingate Anaerobic Test (WAnT). Ten healthy adults (age 21 +/- 1.2 years) volunteered to perform the WAnT on a calibrated Monark 894E cycle ergometer while the EMG and MMG signals were recorded. The EMG and MMG amplitude and power output (W) values per 5-second segments of the test were averaged and normalized to the highest value found during the test, respectively. The statistical analysis indicated that EMG amplitude did not change significantly over the 30-second test, but W and MMG amplitude decreased significantly. There is dissociation between EMG and MMG amplitude over the 30-second anaerobic test, providing evidence that MMG amplitude could be used as a monitor of W during such a task. MMG amplitude could potentially be used as a direct monitor of mechanical activity, which could be of benefit to those who train athletes when a direct assessment of mechanical contribution from a given muscle to a fatiguing activity is desired (such as when monitoring an injury), but it must be studied under various conditions, such as the current study, before such applications are made.

Accuracy of near-infrared interactance instruments and population-specific equations for estimating body composition in young wrestlers.

The purpose of this investigation was to determine the accuracy of near-infrared interactance (NIR) instruments and population-specific NIR equations for estimating percent body fat (% fat) in young wrestlers. Forty-four white male youth wrestlers (mean age +/- SD = 11.0 +/- 2.1 years) volunteered for this study. Thirteen NIR % fat estimates were cross-validated against the criterion % fat from underwater weighing. The results of this study indicated that the total error (TE) values associated with the NIR instrument generated % fat estimates as well as % fat estimates from population-specific NIR equations developed for high school wrestlers or adult men were too large (TE = 5.7-27.3% fat) to be used with young wrestlers. Based on the present findings, it is recommended that new NIR equations be developed and validated specifically for use in young male athletes.

MMG and EMG responses during 25 maximal, eccentric, isokinetic muscle actions.

PURPOSE: The purpose of this study was to examine the patterns of the mechanomyographic (MMG) and electromyographic (EMG) amplitude responses of the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) during 25 maximal, eccentric, isokinetic muscle actions. METHODS: Seven healthy adult females (22.1 +/- 2.4 yr) completed 25 maximal, eccentric muscle actions on a calibrated Cybex 6000 isokinetic dynamometer. EMG and MMG signals were obtained from the VL, RF, and VM during this test, and polynomial regression models were used to examine the relationships for normalized torque, EMG amplitude, and MMG amplitude versus repetition number. RESULTS: There was a cubic relationship (P < 0.05) between torque and repetition number. EMG amplitude demonstrated a positive linear relationship (P < 0.05) for the VL, a quadratic relationship (P < 0.05) for the RF, and no relationship (P > 0.05) for the VM over the 25 repetitions. MMG amplitude demonstrated a negative linear relationship (P < 0.05) for both the VL and VM, and a cubic relationship (P < 0.05) for the RF over the 25 repetitions. CONCLUSION: The results of the present study demonstrated differences between the VL, RF, and VM muscles for the patterns of EMG and MMG responses across the 25 maximal, eccentric muscle actions. These findings suggested that there are muscle-specific motor control strategies during repeated eccentric, isokinetic muscle actions.

MMG and EMG responses during fatiguing isokinetic muscle contractions at different velocities.

The purpose of this study was to determine mechanomyographic (MMG) and electromyographic (EMG) responses of the superficial quadriceps muscles during repeated isokinetic contractions in order to provide information about motor control strategies during such activity, and to assess uniformity in mechanical activity (MMG) between the investigated muscles. Ten adults performed 50 maximal concentric muscle contractions at three randomly selected contraction velocities (60, 180, and 300 degrees.s(-1)) on different days. Surface electrodes and an MMG sensor were placed on the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM). EMG and MMG amplitude and peak torque (PT) were calculated for each contraction, normalized, and averaged across all subjects. The results demonstrated that MMG amplitude more closely tracked the fatigue-induced decline in torque production at each velocity than did EMG amplitude. This indicates that MMG amplitude may be useful for estimating force production during fatiguing dynamic contractions when a direct measure is not available, such as during certain rehabilitative exercises. MMG amplitude responses of the VL, RF, and VM were not uniform for each velocity or across velocities, indicating that it may be possible to detect the individual contribution of each muscle to force production during repeated dynamic contractions. Therefore, MMG amplitude may be clinically useful for detecting abnormal force contributions of individual muscles during dynamic contractions, and determining whether various treatments are successful at correcting such abnormalities.