Relationships Between Force–Time Characteristics of the Isometric Midthigh Pull and Dynamic Performance in Professional Rugby League Players

Abstract

There is considerable conflict within the literature regarding the relevance of isometric testing for the assessment of neuromuscular function within dynamic sports. The aim of this study was to determine the relationship between isometric measures of force development and dynamic performance. Thirty-nine professional rugby league players participated in this study. Forty-eight hours after trial familiarization, participants performed a maximal isometric midthigh pull, with ∼120-130° bend at the knee, countermovement jump (CMJ), and a 10-m sprint. Force-time data were processed for peak force (PF), force at 100 milliseconds (F100ms), and peak rate of force development (PRFD). Analysis was carried out using Pearson's product moment correlation with significance set at p < 0.05. The PF was not related to dynamic performance; however, when expressed relative to body weight, it was significantly correlated with both 10-m time and CMJ height (r = -0.37 and 0.45, respectively, p < 0.05). The F100ms was inversely related to 10-m time (r = -0.54, p < 0.01); moreover, when expressed relative to body weight, it was significantly related to both 10-m time and CMJ height (r = -0.68 and 0.43, p < 0.01). In addition, significant correlations were found between PRFD and 10-m time (r = -0.66, p < 0.01) and CMJ height (r = 0.387, p < 0.01). In conclusion, this study provides evidence that measures of maximal strength and explosiveness from isometric force-time curves are related to jump and sprint acceleration performance in professional rugby league players.

Relationship between isometric mid-thigh pull variables and sprint and change of direction performance in collegiate athletes

“…In this study IPF was related to 5-and 20-m sprint performance which is in agreement with work by Mero et al 33 , and Cunha et al 34 , but in contrast to West et al 13 . Sprint acceleration is heavily reliant on the acceleration of body mass; therefore, based on findings by West et al 13 , absolute measures of IPF are secondary to relative measures, potentially explaining differences to previous findings.…”

“…These findings are similar to West et al 13 , who found PF at 100 ms to significantly correlate to 10 m sprint performance in rugby players. Harris et al 35 has previously found IP relative to body mass to be an important factor in 30-and 40-m sprint performance, therefore it could be assumed IP to be an important factor in sprint performance.…”

“…Sprint acceleration is heavily reliant on the acceleration of body mass; therefore, based on findings by West et al 13 , absolute measures of IPF are secondary to relative measures, potentially explaining differences to previous findings. This was confirmed by significant relationships (r = −0.37 to −0.68) between relative IPF and relative IPF at 100 ms during IMTP testing, and 10 m sprint performance.…”

“…In agreement with these findings, Requena et al 12 observed no relationship (r = −0.35; p > 0.05) between isometric strength with subjects sat in a custommade dynamometric chair, and 15 m sprint performance. However, West et al 13 found significant correlations between isometric mid-thigh pull (IMTP) RFD, absolute and relative PF at 100 ms, and 10 m sprint performance (r = 0.66, 0.54, and 0.68, respectively). Tillin et al 14 found normalized PF at 100 ms during an isometric back squat to correlate to 5-and 20-m sprint performance in rugby players.…”

The Neuromuscular, Biochemical, and Endocrine Responses to a Single-Session Vs. Double-Session Training Day in Elite Athletes

“…It has previously been reported that CMJ correlates well with dynamic performance (47), making it a relevant marker for the assessment of neuromuscular function. A sample rate of 1,000 Hz, and a vertical force range of 20 kN were used for all trials, in accordance with previous research (33).…”