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Original articles  EXERCISE PHYSIOLOGY AND BIOMECHANICS


The Journal of Sports Medicine and Physical Fitness 2008 September;48(3):311-9

language: English

Physiological, biochemical and functional changes induced by a simulated 30 min off-road competitive motocross heat

Ascensão A. 1, 2, Azevedo V. 2, Ferreira R. 1, Oliveira E. 2, Marques F. 3, 4, Magalhães J. 1, 2

1 Research Centre in Physical Activity, Health and Leisure University of Porto, Porto, Portugal
2 Department of Sports Biology Faculty of Sport Sciences, University of Porto, Porto, Portugal
3 Department of Clinical Analysis Faculty of Pharmacy, University of Porto, Porto, Portugal
4 Institute for Molecular and Cell Biology University of Porto, Porto, Portugal


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Aim. Up to now, few studies regarding the impact of motocross heats on functional and physiological variables have been addressed so far. The aim of the present study was to analyze physiological and functional changes induced by a simulated off-road motocross heat.
Methods. Fifteen motocross riders (28.3±7.9 yrs; 71.1±7.0 kg; 169.0±4.0 cm; 53.5±3.7 mL·kg-1·min-1; 14.9±3.3% fat) performed one treadmill running to exhaustion to determine maximal heart rate (HRmax) and maximal oxygen consumption. Thereafter, simulated 30 min competitive off-road motocross heats were performed to measure biochemical (blood lactate and urine catecholamine concentrations) and functional (upper-limb power and fatigue – Wingate and Handgrip) alterations induced by the race. Exercise intensity through HR monitoring, rating of perceived exertion and upper-limb pain were also accomplished.
Results. During the 30 min heats, the riders spent 87% of time above 90% of their HRmax. Significant impairments were observed on maximal isometric handgrip as well as on Wingate variables after the race. Blood lactate concentrations significantly increased from rest vs 10 min, 20 min and final time of analysis (P<0.05). However, a significant decrease was observed between 10 min vs 20 min and final of the race. A significant increase in the 24-h urine catecholamine levels was observed after the race.
Conclusion. The present data suggest that motocross heats are performed at high exercise intensity. Motocross specific effort induces significant functional alterations that may reflect muscle fatigue with consequent decrement on physical performance.

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