The Effects Of Strap Selection On Pain And Force Production During An Isoinertial Device MVIC

Our laboratory’s isoinertial training device has previously been shown to be a reliable and valid instrument for assessing squat maximal voluntary isometric contraction (IMVIC) force using a standard issued waist belt (WB). However, pain associated with tissue compression of the anterior portion of the hips by the WB was prevalent among several participants during WB IMVICs. The IMVIC can also be performed with a full-body harness (FBH), which may disperse the pressure of the strap and make it more tolerable to wear during an IMVIC. Nevertheless, the influence of strap selection on pain and subsequent IMVIC performance is unknown. PURPOSE: To examine differences in participant pain and force production during an FBH and WB squat IMVICs and to examine the reliability and concurrent validity of a FBH IMVIC. METHODS: Twenty (22.40 ± 3.41 yrs, 165.99 ± 7.45 cm, 73.50 ± 17.27 kg, 22.09 ± 9.81BF%) recreationally active men (8) and women (12) completed FBH and WB squat IMVIC assessments followed by a traditional squat MVIC (TMVIC) on two separate occasions. Two-way treatment x time repeated measures ANOVAs were conducted to compare force outputs and pain between treatments (FBH vs. WB) across time. Test-retest reliability was assessed using intraclass correlation coefficients and associations between outcomes were determined using Pearson’s correlation coefficients and stepwise regression. Significance was set at an alpha level of (p ≤ 0.05). RESULTS: FBH and WB IMVIC exhibited excellent test-retest reliability (ICC2,1 = .954 & .967, p = 0.609 & 0.875, respectively) and strong validity (r = 0.813 & 0.821, p < 0.001 & 0.001, respectively) when compared to TMVIC. No significant treatment x time interaction (p = 0.672, ηp2 = 0.010), main effect for treatment (p = 0.243, ηp2 = 0.071), or main effect for time (F1,19 = 0.102, p = 0.753, ηp2 = 0.005) were observed for pain. FBH IMVIC force was significantly higher than WB IMVIC (p = 0.049, ηp2 = 0.189). Nevertheless, WB IMVIC was the only significant predictor of TMVIC (R2 = 0.674, SEE = 46.694). CONCLUSION: Both the FBH and WB IMVIC were shown to be reliable and valid means of assessing squat MVIC. However, considering pain between straps was not significantly different and only WB IMVIC significantly predicted TMVIC, our findings support the use of the WB when assessing squat IMVIC.