ABSTRACT
Israel; 2Child Health and Sport Center, Pediatric Department, Meir Medical Center, Sackler School of Medicine, Tel-Aviv University, Israel
30.1 INTRODUCTION Previous studies have found that prepubescent boys needed less recovery time to sustain peak power output compared to pubescent boys and to young adults during repeated sprints (Ratel et al., 2006). It was also suggested that high level of aerobic fitness is a prerequisite for increased anaerobic performance during repeated sprints in adults (Taylor et al., 1997; Tomlin and Wenger, 2001). However, correlation analyses between 2 max and performance indices of repeated sprint test (RST) have been inconsistent in this population (Meckel et al., 2009). These relationships were never studied in normal weight and overweight children. Therefore, the aim of the present study was to determine the relationship between RST (i.e., 12 x 20 m) and aerobic fitness (measured by the distance completed during 20 m shuttle run test) in pre-and early-pubertal normal weight and overweight children. 30.2 METHODS 30.2.1 Procedure Eighteen normal weigh (35.9±6.3 kg), and fourteen overweight (52.5±10.0 kg) children (10.3±1.5 yrs) performed two tests: a) Aerobic power test - Twenty-Meter Shuttle Run Test. The test consisted of shuttle running at increasing speeds between two markers placed 20 m apart. A portable compact disc (Sony CFD-V7) dictated the pace of the test by emitting tones at appropriate intervals. A starting speed of 8.5 km/hour was maintained for one minute, and thereafter the speed was increased every minute by 0.5 km/hour. The test was terminated when the child withdrew voluntarily from the exercise, or failed to arrive within 3 meters of the end line on two consecutive tones. The
aerobic fitness of each participant was calculated as the number of laps or total distance achieved during the test. b) 12 X 20 m RST. The protocol consisted of 12 X 20 m runs starting every 20 seconds. A photoelectric cell timing system (Alge-Timing Electronic, Austria) linked to a digital chronoscope was used to record each sprint and rest interval time with an accuracy of 0.001 second. The three measures of the RST were the fastest 20 m sprint time (FS), the total sprint time (TS) of the 12 sprints, and the performance decrement (PD) during the test. Total sprint time was calculated as the sum of all sprints times of the test. Performance decrement was used as an indication of fatigue and was calculated as (TS/FS x 12 x 100) – 100 (Fitzsimons et al., 1993). Heart rate was measured using a Polar heart rate monitor (Polar Accurex Plus, Polar Electro, NY) immediately after completion of each run in the RST. Rate of perceived exertion (RPE) was determined using the modified Borg scale (Borg 1982) at the end of the RST.
