THE EFFECTS OF MOUNTAIN BIKE SUSPENSION SYSTEMS ON ENERGY-EXPENDITURE, PHYSICAL EXERTION, AND TIME TRIAL PERFORMANCE DURING MOUNTAIN BICYCLING

The purpose of this 3-Phase study was to investigate the effects of su spension systems on muscular stress, energy expenditure, and time tria l performance during mountain biking. Three suspension systems were te sted, a rigid frame bike (RIG), a suspension fork bike (FS), and a fro nt and rear suspension bike (FSR). Phase I and II consisted of cycling at 16.1 km.hr(-1) over a flat, bumpy course for 63 min. Phase III con sisted of ascending (ATT), descending (DTT), and cross country (XTT) t ime trials. Phase I assessed muscular stress by 24 h change in CK, Pha se II assessed HR, (V) overdot O-2, (V) overdot (E), and Phase III ass essed performance responses to the suspension systems. The 24 hr chang e in CK was greater for RIG than FS and FSR (+ 91.9 +/- 79.5 IU vs +8. 6 +/- 17.5 IU and + 9.7 +/- 21.8 IU). Mean HR was greater for RlG than FS and FSR (153.7 +/- 15.6 bpm vs 146.7 +/- 15.4 bpm, 146.3 +/- 16.2 bpm). Subjects rode significantly faster on FS than FSR and RIG during the XTT (30.9 +/- 2.0 min vs 32.3 +/- 3.6 min, 32.3 +/- 3.2 min). Sub jects RPE was lower for FSR than FS and RIG, however, no differences w ere observed for (V) overdot O-2, (V) overdot (E), ATT, or DTT. Cyclis ts incurred less muscular stress, indicated by CK and HR, when riding the FS and FSR. Although the FS and FSR weigh from 0.7 to 2.2 kg more than RIG, no differences were observed for energy expenditure and that riding the FS in a XTT resulted in a faster finishing time than FSR O F RlG.