Catherine M Shepherd

Data reliability from an instrumented vertical jump platform.

Caruso, JF, Daily, JS, Mclagan, JR, Shepherd, CM, Olson, NM, Marshall, MR, and Taylor, ST. Data reliability from an instrumented vertical jump platform. J Strength Cond Res 24(10): 2799-2808, 2010-A Vertec jump measurement and training system measures vertical jump heights but not additional variables that would reveal how the performance was achieved. Technology advances to equipment now include additional variables that elucidate how jump performance is achieved. However, acceptance of new jump-related equipment is predicated on the reliability of the vertical heights it measures in relation to those assessed by the Vertec. Thus, our study compared vertical jump height reliability data from a newly created instrumented platform to those concurrently derived from the Vertec. Methods required subjects (n = 105) to perform 2 jump trials separated by at least 2 days of rest. Trials began with a warm-up, followed by 3 to 5 maximal-effort jumps. The Vertec was placed directly over the platform so, as jumps occurred, subjects took off and landed on the instrumented device. At the jump apex subjects contacted the highest Vertec slapstick possible to assess maximum height attained. Four height measurements were derived from each jump: 3 platform-based calculations (from subjects take-off, hang time, and landing) and 1 Vertec. The platform-based calculations were compared to Vertec data to assess the reliability of the instrumented device. Intraclass correlation coefficient (0.90), coefficient of variation (17.3%), standard error of measurement (0.9 cm), and smallest real difference (3.7 cm) results showed heights calculated from platform take-offs were most reliable to Vertec values. It was concluded take-off from the platform yielded jump heights that are a viable alternative to those derived from the Vertec. Practical applications suggest coaches may use the platform to derive reliable vertical jump data in addition to other variables to better understand the performance of their athletes.

Front Squat Data Reproducibility Collected With a Triple-Axis Accelerometer

Caruso, JF, Olson, NM, Taylor, ST, McLagan, JR, Shepherd, CM, Borgsmiller, JA, Mason, ML, Riner, RR, Gilliland, L, and Griswold, S. Front squat data reproducibility collected with a triple-axis accelerometer. J Strength Cond Res 26(1): 40–46, 2012—The purpose of our study was to assess data reproducibility from 2 consecutive front squat workouts, spaced 1 week apart, performed by American college football players (n = 18) as they prepared for their competitive season. For each workout, our methods entailed the performance of 3–6 front squat repetitions per set at 55, 65, and 75% of subjects 1 repetition maximum (1RM) load. In addition, a fourth set was done at a heavier load, with a resistance equal to 80 and 83% of their 1RM values, for the first and second workouts, respectively. A triple-axis accelerometer was affixed to a barbell to quantify exercise performance. Per load, the accelerometer measures peak values for the following indices: force, velocity, and power. To assess data reproducibility, inter–workout comparisons were made for 12 performance indices with 4 statistical test-retest measures: intraclass correlation coefficients, coefficients of variation (CVs), and the SEM expressed in both absolute and relative terms. Current results show that the majority of performance indices exceeded intraclass correlation (0.75–0.80) and CV (10–15%) values previously deemed as acceptable levels of data reproducibility. The 2 indices with the greatest variability were power and velocity values obtained at 55% of the 1RM load; thus, it was concluded that higher movement rates at the lightest load were the most difficult aspect of front squat performance to repeat successfully over time. Our practical applications imply lighter loads, with inherently higher rates of barbell movement, yield lower data reproducibility values.

Anthropometry as a predictor of front squat performance in American college football players

To assess the extent anthropometry predicts front squat performance, American college football players (n = 18) performed 3-6 repetition sets at 55, 65, 75 and 80% of their 1RM (one repetition maximum) load across two workouts. At the conclusion of sets, an accelerometer (Myotest Inc., Royal Oak MI) measured peak power, force and velocity. Before the first workout, anthropometric data were collected from subjects that emphasized body segment length ratios in an attempt to predict front squat variance. Via multivariate regression, anthropometry attempted to predict the variance from each of 12 criterion variables (peak power, force and velocity at each load). With an α = 0.05, anthropometry predicted significant amounts of variance for six criterion variables, which also had high R (0.647-0.832) and R 2 (0.419-0.720) values. The same variables also yielded moderate standard error of estimates, thus anthropometry accounted for much front squat performance variance. Height/hip width ratio, body weight, body mass index and torso length were the best predictors of front squat performance. Based on current results, it was concluded anthropometry is an important predictor of front squat performance in American college football players.

β2-Adrenergic Agonist Administration and Strength Training

Abstract β2-Adrenergic agonists (β2AA) produce myriad effects throughout the human body. Prescribed concurrently with theophylline for the bronchodilatory effects they offer in the treatment of asthma and chronic obstructive pulmonary disease, β2AA actions include many beneficial and adverse changes when administered to animals at supraphysiological doses. Beneficial changes include improved musculoskeletal health and function, which can be maintained because adverse changes are reduced if oral β2AA are given at therapeutic dosages in humans with concurrent resistive exercise administration. Combined oral β2AA-resistive exercise treatments have been shown to produce gains in musculoskeletal health and function in numerous healthy and disuse atrophy human models. The mechanism(s) by which β2AA exert their effects are a function of multiple factors, not the least of which includes the type of model receiving the drug treatment. Combined oral β2AA-resistive exercise treatments in humans showed that adverse effects were greatly reduced when prudent and safer drug administration practices were employed (eg, screening subjects for tolerance before drug treatment). Results from human research trials suggest that administration of the combined treatment improves musculoskeletal function and performance with minimal health risk if proper precautions are followed. A related issue is administration of the combined treatment as an ergogenic aid to athletic performance. Given the results presented in this article, physicians should be wary of potential drug abuse and administer β2AA only under appropriate circumstances when such a treatment is warranted.

Data reproducibility from an inertial kinetic exercise machine.

Caruso, JF, Kucera, SC, Hari, PK, Mc Lagan, JR, Olson, NM, Shepherd, CM, and Marshall, MR. Data reproducibility from an inertial kinetic exercise machine. J Strength Cond Res 24(11): 3081-3087, 2010-An inertial kinetic exercise (IKE, Oconomowoc, WI, USA) machine was created that permits high-velocity workouts suited for injury rehabilitation and speed development in athletes. In addition, its design does not entail the movement of resistance against Earths gravitational pull. Thus, the design and operation associated with the IKE may be incorporated into novel environments such as space flight. Yet before it can be used for such reasons, IKE data reproducibility must first be ascertained, which serves as the present studys purpose. Methods to assess data reproducibility required subjects (n = 42) to perform 2 IKE elbow flexor trials, each comprising two 60-second sets separated by a 90-second rest. Preceded by a familiarization session on the IKE, subjects were instructed to perform high-speed elbow flexor trial repetitions in good form. Instrumentation entailed an accelerometer and a computer interfaced with software. Maximum and average forces (MF, AF), as well as work (W), were examined for reproducibility with several test-retest measures. Results showed high reproducibility, yet intertrial variability was greater due in part to the length of time between exercise sessions. It was concluded that MF reproducibility was inherently less partly due to the nature of the variable, which entailed a single instantaneous expression over each 60-second set. In contrast, AF and W denoted a cumulative, and thus better overall, representation of total exercise performance. Based on our high reproducibility values, present IKE instrumentation methods appear to be appropriate. Practical applications suggest that coaches and therapists may want to employ an IKE as instrumented in the present study to derive reproducible performance data on people who may use the device under their supervision.

Reproducibility of vertical jump data from an instrumented platform

To assess the reproducibility of data collected from a newly created instrumented platform that measures vertical jump performance, healthy college-age subjects (n = 178) made three visits to our laboratory. Per jump, the platform offered six performance-related variables: static weight, time to takeoff, peak takeoff force, and maximum jump heights as they ascended, remained in the air and landed. Per subject, the two highest jumps from the final two visits were used to assess data reproducibility. Prior to the reproducibility assessment, Z-scores identified statistical outliers that were removed from subsequent analyses. Paired intra- and inter-jump session data per variable were assessed with the following statistical test-retest tools: intraclass correlation coefficients, coefficient of variation, standard error of measurement, smallest real difference and critical difference. Current results show most data had a high level of reproducibility with few exceptions. Since the platform also has potential applicability in the rehabilitation of disabled persons, future research should assess the data reproducibility associated with gait, balance and mobility collected from the device.

The impact of contractile mode and work volume on the prediction of cortisol concentrations from flywheel-based resistive exercise workouts

To assess cortisol concentrations (CC) from flywheel ergom eter resistive exercise, subjects performed three differe nt leg press workouts on the device. Comprised of ten-repetition sets, the workouts entailed 1): a three-set protocol composed of concentric and eccentric actions (CE3), as well as concentric-only paradigms comprised of 2): three (CO3) and 3): six (CO6) sets. Venous blood draws, collected before workouts and at one and 30 minutes post-exercise, measured CC. ANOVA yielded CC results similar to studies that employed standard resist ive exercise equipment. However multivariate regression revealed body mass, peak angular velocity and average power were strong predictors of post-exercise CC. Separate multivariate analyses of the CE3 and pooled concentric-only (CO3 and CO6 combined) data show differences in level of explained (r 2 ) variance, which was likely due to the ergometers operation. Constant torque ex ertion throughout the CE3 bout meant performance was continual only for that workout and evoked more explained variance versus the concentric-only trials. The current ergometer was originally intended for use aboard manned spacecraft and is a prototype to newer flywheel-based resistive exercise devices. Future research should assess responses to workouts in a bed rest model to determine which protocol best abates CC to further aid future in-flight exercise.

Electromyography and high-speed elbow flexor exercise

Our study assessed motor unit behavior and muscle function from high-speed unilateral elbow flexor workouts. Electromyography and performance data were obtained from subjects who completed three workouts on an Impulse (Impulse Training Systems; Newnan, GA) exercise machine. Comprised of both tonic and phasic repetitions, workouts were done with three different loads (1.13, 3.4 and 6.8 kg) added to the machine. Electromyography was measured from three muscles (biceps brachii, triceps brachii, brachioradialis). Dependent variable means, obtained as the elbow flexed and extended, were compared with 2 (tonic, phasic) x2 (men, women) x3 (1.13, 3.4 and 6.8 kg) ANOVAs, with repeated measures for repetition and load. Bonferronis adjustment preserved family-wise error rates and t-tests served as a post-hoc. With α = 0.05, several dependent variables displayed intra-repetition and -load effects. However triceps root mean square (RMS) values displayed repetition x load interactionsforboth elbowflexion andextension. Thetriceps, an elbowflexionantagonist, may actas animportant joint stabilizer, particularly at faster velocities and more extended joint angles. Unlike isometric or standard low-velocity paradigms performed against heavy loads, high-speed exercise may entail a more equitable distribution among factors (motor unit recruitment, rate coding, reflex potentiation, antagonist co-contraction) responsible for current triceps RMS values.