Jessica R. McLagan

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.

Blood lactate responses to exercise performed on a high-speed inertial device

To assess blood lactate and performance variables obtained from high-speed exercise performed on a device (Impulse Training Systems; Newnan GA) that imposes loads without gravitational resistance, subjects (n = 45) completed two tonic and two phasic workouts. Each high-speed workout entailed two 60-second sets of seated knee- and hip-extension repetitions separated by a 90-second rest period. Pre- and five minutes post-exercise, lactate concentration was measured from a fingertip blood drop with a calibrated analyzer (Accusport, Sports Resource Group, Hawthorne, NY). Mean blood lactate values were compared with a 2(contractile mode: tonic, phasic) x 2(time) x 2 (gender) ANOVA, with repeated measures applied to workout mode and time. Resistance exercise performance variables were assessed with 2 (contractile mode: tonic, phasic) x 2 (gender) ANOVAs. With α ≤ 0.05, results showed a time (post > pre) effect for blood lactate. Exercise performance values were impacted by workout mode and gender, yet those independent variables had no impact on blood lactate. Results concur with prior resistance exercise studies that show significant blood lactate increases over time. Additional inquiry is warranted as to why gender and workout mode influenced resistance exercise performance variables, but did not impact blood lactate.

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 resistive exercise training on the relationship between anthropometry and jump-based power indices

Objective: To examine the impact resistive exercise (RE) training has on the ability of anthropometry to predict power output from jump tests. Methods: With a matched-pairs design, subjects (n = 19) were assigned to six weeks of leg and calf press workouts. With no crossover, subjects either performed RE on a traditional seated leg press device to which free weights (FW) were added, or on a flywheel ergometer (FERG). Before and after the intervention, subjects performed jump-based tests and were measured for anthropometric dimensions. Tests included a standing vertical jump, a repetitive four-jump protocol, and a depth jump from a platform; power outputs from each were calculated. Results: The six-week intervention weakened the correlation between anthropometry and jump-based power indices from FERG workouts, while the opposite was true for the FW group. Conclusions: While several reasons may have led to the stark group differences in the ability to account for jump-based power variance, the two most important factors appear to be the degree of workout progression and the rate RE repetitions were performed. FW subjects incurred significantly greater strength gains, as evidenced by the degree of workout progression over the intervention, versus the FERG group. The manner in which the devices operated permitted FW repetitions to occur at faster rates and was more movement-specific to jump-based tests. Thus anthropometry increased the degree of explained variance in jump-based power indices from FW workouts at the conclusion of the six-week intervention.

The effect of flywheel-based resistive exercise workouts on testosterone/cortisol ratios

Toassessthesubsequent testosterone/cortisol ratio(TCr)fromflywheel-basedresistiveexercise, usingawithin-subjects design volunteers (7men, 10 women) performed three seated legpress workouts on an ergometer (YoYoTechnologies, Stockholm Sweden). Comprised of ten-repetition sets, the workouts entailed: a three-set protocol composed of concentric and eccentric actions (CE3), as well as concentric-only paradigms of three (CO3) and six (CO6) sets. Venous blood, collected before bouts and at one and 30 minutes post-exercise, was used to quantify the TCr. Data were examined with ANOVA and multivariate regression. ANOVA yielded a gender x time TCr interaction, as male values declined significantly yet womens data were unchanged. With the TCr at one and 30 minutes post-exercise as separate criterion measures, and data pooled across genders and workouts, multivariate regression revealed significance per dependent variable. Univariate correlations showed the best predictors of the post-exercise TCr in descending order were: body mass, average power and delta lactate. Gender and quadriceps muscle volume may have acted as confounding variables to allow body mass to the best current study predictor. Continued research should examine additional predictor variables, as current results only accounted for roughly 30% of the total criterion measure variance.