A Technique for Assessing the Global Fatigue State During Maximal Cylcing: 1259 Board #52 May 28, 9

Fatigue has been reported to reduce both maximum torque and maximum pedaling rate during maximal cycling. This dual effect alters the shape of the power-pedaling rate curve and may confound evaluation of fatigue because a single fatigue state will exhibit different fatigue at different pedaling rates. Providing a global representation of a specific fatigue state requires data at two or more pedaling rates. Obtaining measures at two pedaling rates that represent the same fatigue state poses unique challenges and requires an isokinetic ergometer capable of rapid rate changes. Indeed, the technique previously used to demonstrate changes in maximum torque and maximum pedaling rate may have been confounded by additional fatigue within the measurement period. PURPOSE: Demonstrate the feasibility of a technique to determine fatigue during maximal cycling at two pedaling rates and use those measured values to quantify the global fatigue state. METHODS: Seven cyclists performed fatiguing maximal isokinetic cycling for 25s. Power was recorded at 2 Hz. For the first 20s, the pedaling rate was controlled at 90 rpm and then changed to 150 rpm. The system stabilized at the new second pedaling rate in ~2s. Linear regression of power-time data was used to estimate the power that would have been produced at a single time point within the transition period for each pedaling rate. Torque was calculated from the two power-pedaling rate values and used to establish torque- and power-pedaling rate relationships. A value to represent the global fatigue state (GFS) was calculated by integrating the power-pedaling rate relationship from zero to maximum pedaling rate. Fatigue index values were calculated from power (Δ power/rested power) at 90 and 150 rpm and from GFS values. Fatigue index values were compared using separate paired Student’s t-tests. RESULTS: Fatigue index was significantly greater when assessed at 150 rpm than at 90 rpm (59±9% vs. 35±5%, p<0.001). Fatigue index calculated from GFS values was 54±6%. CONCLUSION: We have demonstrated a method for evaluating fatigue at two pedaling rates and used the data to produce a value representing a global fatigue state. Because fatigue changes the shape of the power pedaling rate relationship this method provides a more thorough assessment of fatigue than could be obtained using a single pedaling rate. We believe this method will provide novel insight when used in a variety of fatigue protocols.