Acute exposure to vibration has been suggested to produce transient increases in muscular strength (1,2,8), vertical jump displacement (4,8), and power output (2,6,7) recorded while performing various tasks. It has been hypothesized that the reported acute vibration induced increases in performance occur as a result of alterations in neuromuscular stimulation (1,3,4). Specifically, most studies have ascribed the observed improvements to the likeliness of Whole Body Vibration (WBV) in producing a “tonic vibration reflex” (TVR) in which the primary nerve endings of the Ia afferents of the muscle spindle are activated. This is thought to result in the excitation of the alpha-motor neurons and activation of the extrafusal fibers (4) which likely leads to a greater synchronization of motor units as a result of homonymous motor unit contraction. However, not all investigations report improvements in muscular strength (4), vertical jump (7), and power production in response to acute vibration (4). While the current body of scientific knowledge offers conflicting evidence on the effectiveness of WBV in augmenting neuromuscular performance it is possible that WBV may result in alterations to specific aspects of the force-time curve during the performance of a maximal isometric contraction. Therefore, the primary purpose of this investigation was to examine the effects of WBV performed using 30 Hz frequency and 2-4 mm amplitude on the force-time curves of an isometric mid-thigh pull.

Abstract available in the Medicine and Science in Sports and Exercise.

Currently, multi-joint, position-specific isometric tests (MJIT) are commonly used as part of the monitoring of an athlete’s progress. Strong associations between isometric force-time curve parameters have been found. Perhaps the most commonly used test is the isometric mid-thigh pull (IMTP): the IMTP was created in the early 1990s and its use has grown considerably since that time. One sport in which it has been used extensively from the early 1990s to the present, particularly by the authors, is weightlifting. The relationships between weightlifting performance and IMTP force-time characteristics are quite strong, particularly for RFD. The IMTP is not only useful in assessing a weightlifter’s performance but can also be used for monitoring fatigue.

The purposes of this study were to examine the relationships between dynamic strength index (DSI) and other strength-power performance characteristics and to contextualize DSI scores using case study comparisons. 88 male and 67 female NCAA division I collegiate athletes performed countermovement jumps (CMJ) and isometric mid-thigh pulls (IMTP) during a pre-season testing session as part of a long-term athlete monitoring program. Spearman's correlations were used to assess the relationships between DSI and CMJ peak force, height, modified reactive strength index, peak power and IMTP peak force and rate of force development (RFD). Very large relationships existed between DSI and IMTP peak force (r = -0.848 and -0.746), while small-moderate relationships existed between DSI and CMJ peak force (r = 0.297 and 0.313), height (r = 0.108 and 0.167), modified reactive strength index (r = 0.174 and 0.274), and IMTP RFD (r = -0.341 and -0.338) for men and women, respectively. Finally, relationships between DSI and CMJ peak power were trivial-small for male (r = 0.008) and female athletes (r = 0.191). Case study analyses revealed that despite similar DSI scores, each athlete's percentile rankings for each variable and CMJ force-time characteristics were unique, which may suggest different training emphases are needed. Based on the explained variance, an athlete's IMTP performance may have a larger influence on their DSI score compared to the CMJ. DSI scores should be contextualized using additional performance data to ensure each individual athlete receives the appropriate training stimulus during different training phases throughout the year.

The purpose of this study was to investigate the kinetic and morphological adaptations that occur during distinct phases of a block periodized training cycle in weightlifters. Athlete monitoring data from nine experienced collegiate weightlifters was used. Isometric mid-thigh pull (IMTP) and ultrasonography (US) results were compared to examine the effects of three specific phases of a training cycle leading up to a competition. During the high volume strength-endurance phase (SE) small depressions in rate of force development (RFD) but statistically significant (p ≤ 0.05) increases in vastus lateralis cross-sectional area (CSA), and body mass (BM) were observed. The lower volume higher intensity strength-power phase (SP) caused RFD to rebound above pre-training cycle values despite statistically significant reductions in CSA. Small to moderate increases only in the earlier RFD time bands (ms) occurred during the peak/taper phase (PT) while CSA and BM were maintained. Changes in IMTP RFD and CSA from US reflected the expected adaptations of block periodized training phases. Changes in early (ms) and late (≥150 ms) RFD time bands may not occur proportionally throughout different training phases. Small increases in RFD and CSA can be expected in well-trained weightlifters throughout a single block periodized training cycle.

This dissertation aimed to explore the usefulness of using force derivatives for onset detection in the isometric mid-thigh pull test. First, we examined applications of three differential calculus principles, first and second derivative, and curvature using visual detection as a reference under different baseline conditions. Second, we compared the best derivative method to a threshold-based method using visual detection as a reference. Results of our first investigation showed trivial differences between many differential calculus methods and visual detection. However, statistical differences exceeding a trivial effect was observed when instantaneous force and rate of force develop were examined. Through the first investigation, first and second derivative emerged as possible viable methods for baseline with a countermovement and for all other baseline conditions, respectively. Results of the second investigation showed similarities to the first investigation with respect to onset time. However, examination of instantaneous force and rate of force development indicated that a threshold-based method tended to overestimate compared to visual detection and a first and second derivative combined method. In fact, the difference between visual detection and the first and second derivative combined method ranged from trivial to moderate under all baseline conditions while the threshold-based method often reached a large difference. Overestimation by the threshold-method was more pronounced for rate of force development. In conclusion, while not perfect, the first and second derivative 3 combined method appears to hold possible practical potential and may be used as an assistant method for entry-level sport scientist plus using visual detection for obvious erroneous values.

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Objectives: To determine if force differences exist between isometric pulling positions corresponding to key positions of the deadlift. Design: Cross-sectional evaluation of isometric strength Methods: 14 powerlifters performed isometric pulls on a force plate at 3 key positions related to the deadlift (at the floor, just above the patella, and 5-6 cm short of lockout) and in the mid thigh pull position (MTP). A 1x4 repeated measures ANOVA was used to ascertain differences between the various pulling positions tested. Bonferroni-adjusted paired samples t-tests were used post-hoc. Results: Forces generated at each bar height were significantly different (F(3,39) = 51.058, p2=0.80). Paired samples t-tests showed significant differences between positions, revealing a trend of greater force generation at increasing heights for positions corresponding to the deadlift. Force generated in the mid thigh pull position was significantly higher than any other position. Conclusion: In positions corresponding to the deadlift, force generation increases at higher bar heights.

Monitoring tests are commonly used to assess weightlifter’s preparedness for competition. Although various monitoring tests have been used, it is not clear which test is the strongest indicator of weightlifting performance. Therefore, the purpose of this study was to (1) determine the relationships between vertical jump, isometric mid-thigh pull (IMTP) and weightlifting performance; and (2) compare vertical jumps to IMTP as monitoring tests of weightlifting performance in a large cohort of male and female weightlifters. Methods: Fifty-two competitive weightlifters (31 males, 21 females) participated in squat and countermovement jump testing (SJ, CMJ), and IMTP testing performed on force plates. All laboratory testing data was correlated to a recent competition where the athletes had attempted to peak. Results: Squat jump height (SJH) was the strongest correlate for men and women with the Sinclair Total (r = 0.686, p ≤ 0.01; r = 0.487, p ≤ 0.05, respectively) compared to countermovement jump height (r = 0.642, p ≤ 0.01; r = 0.413, p = 0.063), IMTP peak force allometrically scaled to body mass (r = 0.542, p ≤ 0.01; r = −0.044, p = 0.851) and rate of force development at 200 ms (r = 0.066, p = 0.723; r = 0.086, p = 0.711), respectively. Further, SJH was a stronger correlate of relative weightlifting performance compared to IMTP peak force in females (p = 0.042), but not male weightlifters (p = 0.191). Conclusions: Although CMJ and IMTP are still considered strong indicators of weightlifting performance, SJH appears to be the most indicative measure of weightlifting performance across a wide-range of performance levels. Thus, SJH can be used as a reliable measure to monitor weightlifting performance in male and female weightlifters.

Repeat sprint ability has been investigated thoroughly, however optimal training methodology to improve RSA remains elusive. Both kinetic and physiological viewpoints have been used to scrutinize aspects of RSA including, initial sprint performance (anaerobic power), maximal cardiorespiratory fitness (VO2max), lactate threshold, anaerobic capacity (mean power), muscle activation (EMG), and local muscle oxygenation kinetics. To our knowledge no study has utilized maximal strength levels as a separate factor among a homogenous group of cardiorespiratory fitness individuals (as determined by peak VO2 during RSA). The purpose of this study was to better understand the relationship between maximal strength, muscular characteristics, and cycling RSA- respective to muscle oxygenation responses. Fifteen participants completed fifteen 10-second maximal effort sprints on a cycle ergometer interspersed with 30-seconds passive recovery. Respiratory, muscle oxygenation, and kinetic responses were monitored continuously and evaluated relationships with maximal strength and muscular architecture as determined by isometric mid-thigh pull and ultrasonography respectively. A series of 2 x 15 mixed design, group x time, ANOVA’s were used to evaluate the effects of group and or sprint on muscle oxygenation kinetics. Strong individuals were found to have significantly greater levels of muscle oxygenation usage, recovery and the respective rates; p = 0.01, p = 0.02, p