The reliability of the intermittent critical velocity test and assessment of critical rest interval in men and women

The purpose of this study was to examine the reliability of the intermittent critical velocity (ICV) test and assess critical rest interval (CRI) during repeated-sprint exercise. The ICV test is used to examine the linear relationship between total distance and time-to-exhaustion during interval exercise, yielding a repeatable, moderate-intensity parameter (ICV), a high-intensity exhaustive parameter (W′), and CRI. CRI is the theoretical rest period needed to complete a series of repeated bouts of exercise without fatigue. Twenty-four healthy college-aged men (mean ± SD; age 22.7 ± 2.9 years; weight 85.8 ± 15.3 kg; VO_2max 50.7 ± 8.8 ml/kg/min) and women (mean ± SD; age 21.4 ± 2.3 years; weight 58.9 ± 5.2 kg; VO_2max 46.4 ± 4.4 ml/kg/min) participants completed two ICV tests (T1 and T2), using 10 s repeated sprints to exhaustion during separate sessions of treadmill running. Linear regression was used to determine ICV and W′, while CRI was calculated using the relationship between the number of intervals completed and a variant of ICV. Intraclass correlation coefficients (ICCs) for ICV, W′, and CRI were 0.89 (T1 4.42 ± 0.55 m/s; T2 4.34 ± 0.67 m/s), 0.80 (T1 125.6 ± 62.7 m; T2 144.6 ± 65.4 m), and 0.59 (T1 23.9 ± 2.0 s; T2 24.5 ± 2.6 s), respectively. These moderate to high ICC values indicate reliable measurements between ICV trials. Additionally, the evaluation of CRI demonstrated the attainment of a steady-state heart rate (94% of maximum) during a separate session of repeated supramaximal treadmill sprints. The ICV test during treadmill running provides reliable ICV and W′ measures, as well as an estimated recovery time via CRI for men and women.