Aim: To evaluate the reliability of isometric peak force (IPF) in a novel "long-length" 90°Hip:20°Knee (90:20) strength test and to compare the simulated soccer match induced fatigue-recovery profile of IPF in this test with that of an isometric 90°Hip:90°Knee (90:90) position test.
Methods: Twenty semi-professional soccer players volunteered for the study of which 14 participated in the first part of the study which assessed 90:20 reliability (age = 21.3 ± 2.5 years, height = 1.79 ± 0.07 m, body mass = 73.2 ± 8.8 kg), while 17 completed the second part of the study evaluating fatigue-recovery (age 21.2±2.4 yrs., height = 180 ± 0.09 m, body mass 73.8 ± 8.9 kg). We evaluated the inter-session reliability of IPF in two 90:20 test protocols (hands on the wall (HW); and hands on chest (HC)) both performed on two occasions, 7 days apart. We then assessed 90:20 (HC) and 90:90 IPF immediately before (PRE) and after (POST) after a simulated soccer match protocol (BEAST90mod) and 48 (+48 h) and 72 hours (+72 h) later.
Results: Part one: the 90:20 showed moderate to high overall reliability (CV's of 7.3% to 11.0%) across test positions and limbs. CV's were lower in the HW than HC in the dominant (7.3% vs 11.0%) but the opposite happened in the non-dominant limb where CV's were higher in the HW than HC (9.7% vs 7.3%). Based on these results, the HC position was used in part two of the study. Part two: 90:20 and 90:90 IPF was significantly lower POST compared to PRE BEAST90mod across all testing positions (p<0.001). IPF was significantly lower at +48 h compared to PRE in the 90:20 in both limbs (Dominant: p<0.01,Non-dominant: p≤0.05), but not in the 90:90. At +72 h, IPF was not significantly different from PRE in either test.
Conclusions: Simple to implement posterior IPF tests can help to define recovery from competition and training load in football and, potentially, in other multiple sprint athletes. Testing posterior chain IPF in a more knee extended 90:20 position may provide greater sensitivity to fatigue at 48 h post simulated competition than testing in the 90:90 position, but also may require greater degree of familiarization due to more functional testing position.