Gross Efficiency During Flat and Uphill Cycling in Field Conditions

PURPOSE

Whilst a number of studies investigated gross efficiency (GE) in laboratory conditions, few studies have analyzed GE in field conditions. Therefore, the aim of this study was to analyze the effect of gradient and cadence on GE in field conditions.

METHODS

Thirteen trained cyclists (mean ± SD age: 23.3 ± 4.1 years; stature: 177.0 ± 5.5 cm; body mass: 69.0 ± 7.2 kg; VO2max 68.4 ± 5.1 mL·min-1·kg-1) completed an incremental graded exercise test to determine the ventilatory threshold (VT) and 4 field trials of 6 min duration at 90% of VT on flat (1.1%) and uphill terrain (5.1%) with two different cadences (60 and 90 rev·min-1). Oxygen uptake was measured with a portable gas analyzer and power output was controlled with a mobile power crank, which was mounted on a 26-inch mountain bike.

RESULTS

GE was significantly affected by cadence (20.6 ± 1.7% vs. 18.1 ± 1.3% at 60 and 90 rev·min-1, respectively; P<0.001) and terrain (20.0 ± 1.5% vs. 18.7 ± 1.7% at flat and uphill cycling, respectively; P=0.029). The end-exercise oxygen uptake was 2536 ± 352 mL·min-1 and 2594 ± 329 mL·min-1 for flat and uphill cycling, respectively (P=0.489). There was a significant difference in end-exercise oxygen uptake between the 60 (2352 ± 193 mL·min-1) and the 90 rev·min-1 (2778 ± 431 mL·min-1) (P<0.001).

CONCLUSION

This findings support previous laboratory based studies demonstrating reductions in GE with increasing cadence and gradient that might be attributed to changes in muscle activity pattern.