Physiologic effects of directional changes in intermittent exercise in soccer players.

The aim of the present study was to compare the physiologic impact of intermittent exercise in specific shuttle running (IS), which requires 180° directional changes, and traditional in-line (IL) running. Ten elite male adult soccer players performed different intermittent exercises according to their maximal aerobic velocity (ν&OV0312;O2max): 30-30 seconds at 100% (30 s of runs at 100% of ν&OV0312;O2max alternated with 30-s recovery period), 105%, and 110% of ν&OV0312;O2max with active recovery, 15-15 seconds at 105%, 110%, and 115% of ν&OV0312;O2max, and 10-10 seconds at 110%, 115%, and 120% of ν&OV0312;O2max with passive recovery. Each exercise was performed in the IL and IS format in a randomized order. Heart rate (HR) expressed in percentage of HR reserve (HRres), postexercise blood lactate concentration [La], and ratings of perceived exertion (RPE) were recorded. The different 30-30 seconds showed significantly higher HRres responses in IS compared with IL (p < 0.01). The [La] and RPE results indicated higher values in IS. In conclusion, the physiologic impact of specific IS is substantially higher than in traditional IL. The changes of direction induce an increase in the anaerobic metabolism solicitation and consequently create different responses compared with traditional IL running. This information can aid coaches in the design of intermittent training programs using classical (IL) or a specific form (IS) of running to induce different physiologic responses.