![]() This has been modeled to RSE, and identifies a novel fatigue threshold known as the intermittent critical velocity (iCV) ( 12, 13). A well-known feature of steady-state high-intensity exercise is the curvilinear relationship between running velocity and time to exhaustion, termed critical velocity or critical speed ( 5). RSA provides evidence for the presence of fatigue, but it fails to define a threshold where fatigue increases during RSE ( 11). Resistance to fatigue during RSE is known as repeated-sprint ability (RSA) ( 14), and characterized by a reduction in velocity/power output from a series of short ( 30 sec) ( 7, 11). Many team-sport athletes perform repeated maximal or near-maximal effort sprints interspersed with recovery over 1–4 h, known as repeated sprint exercise (RSE) ( 14). A single dose of caffeine consumed 60 min before repeated-sprints can improve performance at 110% vVO 2max, but not at higher velocities. Caffeine did not improve iCV model parameters. Caffeine ingestion increased running duration at 110% vVO 2max ( p = 0.02), but not at 120 ( p = 0.93) and 130% vVO 2max ( p = 0.14). Total distance and duration were recorded to determine exercise tolerance using the iCV model. Each bout continued until volitional exhaustion and was separated by 20 min of passive rest. ![]() The treadmill grade and velocity at VO 2max (vVO 2max) were used for iCV testing, and consisted of 3 bouts (10 sec running and 10 sec passive rest) at 130, 110 and 120% vVO 2max. Seven physically active men (age = 21.6 ± 1.5 years, body mass = 72.8 ± 5.1 kg, VO 2max = 56.9 ± 9.8 mL/kg/min) ingested caffeine (5 mg/kg) or placebo (crossover design) 60 min prior to an intermittent critical velocity (iCV) test. iCV is a running velocity that distinguishes intermittent running velocities (velocities ≤ iCV) that are sustainable from those resulting in a predictable time to exhaustion (velocities > iCV). This research determined if caffeine improved exercise tolerance during repeated-sprint exercise. Caffeine improves short-to-moderate distance running performance, but the effect of caffeine on repeated sprints are equivocal.
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