Isometric Squat Assessment Does Not Sensitively Monitor Force Impairments Following Resistance Exercise

PURPOSE: To assess the ability of the isometric squat assessment to monitor force impairments following a bout of high-volume of resistance exercise. METHODS: Ten resistance-trained women [62.4 ± 6.6 kg; 1.26 ± 0.15 relative strength (1-RM, kg/kg body mass)] completed eight sets of 10 repetitions of 70% 1-RM back squat. The ISQT was implemented via a power rack with two inverted J-hooks and a standard barbell. Participants were instructed to hold a quarter-squat, such that the height of the barbell was at 75% of their upright stature and upon a verbal cue, push forcefully into the barbell. They were familiarized with the assessment prior to the experimental trial, which they completed prior to exercise (PRE), as well as immediately (IP), 1-(1H), 24- (24H), and 48-hours (48H) after exercise. ISQT data includes rate of force development (RFD), force, and impulse (IMP) across different time bands. At each timepoint, three assessments were performed and averaged. A mixed-model regression was utilized to observe changes over time. Alpha for significance set at α < 0.05. RESULTS: There were no significant changes over time for RFD at 30 ms (F = 1.411, p = 0.270), 50 ms (F = 1.176, p = 0.365), 90 ms (F = 0.950, p = 0.459), 100 ms (F = 0.961, p = 0.450), 150 ms (F = 0.934, p = 0.461), 200 ms (F = 0.529, p = 0.716), 250 ms (F = 0.360, p = 0.834). Nor were there changes over time for peak force (F = 2.303, p = 0.088), force at 30 ms (F = 2.292, p = 0.090), 50 ms (F = 2.314, p = 0.087), 100 ms (F = 2.304, p = 0.088), 200 ms (F = 2.255, p = 0.094), 500 ms (F = 2.288, p = 0.090), 1000 ms (F = 2.520, p = 0.068), or 5000 ms (F = 2.369, p = 0.056). Similarly, there were no observed changes across time for IMP at 100 ms (F = 0.999, p = 0.437), 200 ms (F = 1.117, p = 0.383), or 300 ms (F = 1.341, p = 0.293). CONCLUSION: The ISQT does not sensitively measure expected decrements of RFD, force, and IMP following resistance exercise. Other performance assessments should be implemented to monitor these force impairments. - Measure Timeband PRE IP 1H 24H 48H RFD (N/ms) 0-30ms 1745.63 (1323.18) 2054.33 (1077.58) 1715.20 (1349.20) 1411.30 (842.91) 1866.78 (1147.73) 30-50ms 1715.13 (1217.17) 1862.89 (891.98) 1580.30 (199.65) 1430.90 (730.77) 2056.78 (1985.84) 50-90ms 1536.00(115.71) 1767.11 (822.51) 1446.4 (1051.42) 1450.30 (703.85) 1634.33 (1026.71) 90-100ms 1507.00 (1152.55) 1749.33 (809.00) 1418.90 (1021.01) 1443.10 (674.67) 1585.00 (905.15) 100-150ms 1506.25 (1078.42) 1679.67(814.44) 1346.3 (828.46) 1401.9(544.38) 1419.67(653.75) 150-200ms 1447.00 (1026.42) 1579.56(743.15) 1335.10(657.78) 1348.80(425.41) 1284.89(551.81) 200-250ms 1325.50(895.10) 1452.22(661.56) 1293.20(543.21) 1277.90(381.44) 1175.22(470.75) Force (N) Peak 807.50(328.63) 760.22(264.61) 779.00(241.40) 835.80(281.45) 792.33(268.66) 0-30ms 805.13(327.73) 758.00(263.99) 775.40(241.25) 833.10(281.10) 788.11(269.23) 30-100ms 800.88(326.43) 752.22(263.14) 769.30(238.76) 826.90(279.77) 781.77(268.22) 100-200ms 798.13(325.04) 749.22 (262.74) 766.50 (238.38) 822.80 (279.94) 777.11 (269.94) 200-500ms 788.50(322.07) 739.11 (261.17) 758.60 (236.32) 813.50 (277.62) 768.44 (266.92) 500-1000ms 770.5 (311.62) 722.78 (257.08) 745.50(232.28) 804.30 (274.64) 753.78 (259.64) 1000-5000ms 663.88(247.57) 610.00(198.11) 650.30(193.59) 659.90(197.60) 642.78(188.88) IMP (N/ms) 0-100ms 23.38 (20.53) 12.56 (5.34) 15.60 (9.47) 12.70 (9.10) 17.00 (11.03) 100-200ms 61.25 (37.88) 40.67 (15.90) 44.70 (20.37) 39.10 (30.41) 46.78 (22.67) 200-300ms 108.50 (55.09) 79.78 (29.55) 84.40 (30.77) 75.50 (31.16) 85.33 (33.82) Data is presented as Mean (SD).