Relationships Between Tests of Strength, Power, and Speed and the 75-Yard Pursuit Run.

ABSTRACT: Post, BK, Dawes, JJ, and Lockie, RG. Relationships between tests of strength, power, and speed and the 75-yard pursuit run. J Strength Cond Res 36(1): 99-105, 2022-The 75-yard pursuit run (75 PR) was designed to simulate a foot pursuit for law enforcement officers (LEOs). Currently, there has been no analysis of contributing physiological factors to performance in this test. The study purpose was to determine the relationships between the 75 PR and tests of linear speed, change-of-direction (COD) speed, and lower-body power and strength. Forty-three subjects (21 men and 22 women) completed 2 testing days. Day 1 consisted of the 75 PR, and linear speed (5- and 20-m sprint intervals) and lower-body power (standing broad jump, best lateral jump regardless of leg) tests. Day 2 included the COD speed (Illinois agility test [IAT], best 505 regardless of leg), lower-body power (vertical jump [VJ]), and strength (isometric mid-thigh pull: peak force, normalized peak force [nPF]) tests. Pearson's (men and women) and partial (combined controlling for sex) correlations (p < 0.05) determined relationships between the 75 PR and the performance tests. Significant relationships were found between the 75 PR and the jump tests (r = -0.53 to -0.68), 20-m sprint interval, IAT, and 505 (r = 0.55-0.82) in men, and between the 75 PR and the jump tests, nPF (r = -0.56 to -0.79), sprint intervals, IAT, and 505 in women (r = 0.54-0.84). When sexes were combined, significant relationships were observed between the 75 PR and the jump tests, nPF (r = -0.41 to -0.67), sprint intervals, IAT, and 505 (r = 0.43-0.78). Prospective LEOs should develop linear and COD speed, lower-body power, and relative strength to improve foot pursuit ability.

Physical Qualities Pertaining to Shorter and Longer Change-of-Direction Speed Test Performance in Men and Women.

This study investigated relationships between shorter (505, change-of-direction (COD) deficit as a derived physical quality) and longer (Illinois agility test; IAT) COD tests with linear speed, lower-body power (multidirectional jumping), and strength in recreationally-trained individuals. Twenty-one males and 22 females (similar to collegiate club-sport and tactical athletes) were assessed in: 505 and COD deficit from each leg; IAT; 20 m sprint; vertical jump (VJ height, peak anaerobic power measured in watts (PAPw), power-to-body mass ratio); standing broad jump; lateral jump (LJ) from each leg; and absolute and relative isometric midthigh pull (IMTP) strength. Partial correlations calculated sex-determined relationships between the COD and performance tests, with regression equations calculated (p < 0.05). The 505 and IAT correlated with all tests except PAPw and absolute IMTP (r = ±0.43⁻0.71). COD deficit correlated with the LJ (r = -0.34⁻0.60). Left- and right-leg 505 was predicted by sex, 20 m sprint, and left-leg LJ (70⁻77% explained variance). Right-leg COD deficit was predicted by sex and left-leg LJ (27% explained variance). IAT was predicted by sex, 20 m sprint, right-leg LJ, and relative IMTP (84% explained variance). For individuals with limited training time, improving linear speed, and relative lower-body power and strength, could enhance shorter and longer COD performance.

Quadriceps Impairment Is Associated with Gait Mechanics in Young Adults with Obesity.

PURPOSE: Obesity influences gait and muscle function, which may contribute to knee osteoarthritis. This study aimed 1) to compare gait biomechanics and quadriceps function between individuals with and without obesity and 2) to examine the association between quadriceps function and gait biomechanics. METHODS: Forty-eight individuals with and 48 without obesity participated and were matched on age and sex. Gait biomechanics at standardized and self-selected speeds were used to assess peak vertical ground reaction force (vGRF), vertical loading rate (vLR), internal knee extension moment (KEM), peak knee flexion angle (KFA), knee flexion excursion (KFE), and knee joint stiffness. Quadriceps function was assessed using peak isometric strength (peak torque), early (RTD100) and late (RTD200) rate of torque development (RTD), and vastus lateralis cross-sectional area (CSA) and echo intensity (EI). RESULTS: When normalized to fat-free mass, individuals with obesity had lower RTD100 (P = 0.04) and RTD200 (P = 0.02) but higher vastus lateralis CSA (P < 0.01) and EI (P < 0.01) compared with normal weight controls. The group-speed interaction was significant for normalized vGRF (P < 0.01), normalized vLR (P = 0.02), normalized KEM (P = 0.03), and normalized knee joint stiffness (P = 0.02). Post hoc analyses indicate a smaller normalized vGRF and normalized KEM, and lower knee joint stiffness in individuals with obesity compared with normal weight controls at self-selected speed. There were main effects of speed for all kinematic and kinetic variables, and body mass index group for all absolute kinetic variables as well as normalized vGRF (all P < 0.001). A lower vastus lateralis EI (P = 0.04) and greater RTD100 (P < 0.01) were associated with a larger KEM in individuals with obesity. CONCLUSION: Individuals with obesity have quadriceps dysfunction that is weakly associated with KEM during walking. Exercise interventions that improve quadriceps function may improve walking mechanics.