This study examines the relationship between inspiratory muscle performance (IMP) using the Test of Incremental Respiratory Endurance (TIRE), knee extension (EXT) and flexion (FLEX) acceleration (ACCEL) and deceleration (DECEL) times on an isokinetic dynamometer (ID), and performance of the Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1) among thirteen Division I collegiate women soccer players (D1CWSP). Knee EXT and FLEX were tested at three velocities (60°/s, 180°/s, and 300°/s) using ID, while IMP was measured using maximal inspiratory pressure (MIP) and sustained maximal inspiratory pressure (SMIP). Significant negative correlations were found between MIP and the ACCEL time of FLEX at 60°/s and 300°/s, as well as between MIP and the DECEL time of EXT at 180°/s. Additionally, SMIP was negatively correlated with ACCEL times of FLEX at 180°/s and 300°/s and with DECEL times for both EXT and FLEX at 300°/s. These results suggest that greater IMP is linked to faster ACCEL and DECEL times in knee EXT and FLEX, indicating a role of IMP in enhancing muscle recruitment and performance. The only significant correlation with the YYIRT1 performance was observed between the YYIRT accumulated distance and the ACCEL time of FLEX at 180°/s. These findings highlight a physiological mechanism whereby IMP may contribute to improved dynamic muscle performance, though further research is needed to explore its implications for overall athletic performance.

Background: Evidence describing position-related physical characteristics in women’s soccer is growing, but positional differences in laboratory measures are inconsistent, and inspiratory muscle performance has rarely been examined alongside lower-extremity dynamometry. This exploratory pilot study compared dominant-leg knee isokinetic and inspiratory muscle outcomes in Division I collegiate women’s soccer midfielders and non-midfielders. Methods: Eleven players (5 midfielders, 6 non-midfielders) completed concentric knee extension/flexion testing at 60, 180, and 300 deg/s and the Test of Incremental Respiratory Endurance assessment. Because of the small sample and number of outcomes, exact two-sided Mann–Whitney U tests were used, rank-biserial correlations described effect magnitude, and Holm-adjusted p-values were examined within exploratory outcome families defined for this revision. Results: Several unadjusted isokinetic comparisons favored non-midfielders. Extension maximal-repetition total work (MRTW) at 60 deg/s was the only comparison with a within-family Holm-adjusted p < 0.05 (exact p = 0.004; Holm-adjusted p = 0.043). A sensitivity analysis using the alternative archived 60-deg/s set preserved the direction and large effect magnitude (U = 1, exact p = 0.009, r_rb = 0.93), supporting consistency of the exploratory signal across sets. Inspiratory outcomes were not statistically different; SMIP was 380.8 +/− 148.1 PTU in midfielders and 495.0 +/− 92.9 PTU in non-midfielders (U = 5, exact p = 0.082; r_rb = 0.67). Conclusions: In this small exploratory sample, non-midfielders tended to demonstrate higher absolute values across selected knee isokinetic outcomes, but most findings did not remain below 0.05 after within-family multiplicity adjustment, and inspiratory outcomes were inconclusive. These results are hypothesis-generating and require confirmation in larger, position-specific cohorts under standardized testing conditions.