Acute effects of fatigue on internal and external load variables determining cyclists' power profile.

The aim of the present study was to determine whether fatigue affects internal and external load variables determining power profile in cyclists. Ten cyclists performed outdoor power profile tests (lasting 1-, 5 and 20-min) on two consecutive days, subject either to a fatigued condition or not. Fatigue was induced by undertaking an effort (10-min at 95% of average power output obtained in a 20-min effort followed by 1-min maximum effort) until the power output decreased by 20% compared to the 1-min power output. Fatigued condition decreased power output (p < 0.05, 1-min: 9.0 ± 3.8%; 5-min: 5.9 ± 2.5%; 20-min: 4.1 ± 1.9%) and cadence in all test durations, without differences in torque. Lactate decreased in longer efforts when a fatigue protocol had previously been conducted (e.g., 20-min: 8.6 ± 3.0 vs. 10.9 ± 2.7, p < 0.05). Regression models (r2 ≥ 0.95, p < 0.001) indicated that a lower variation in load variables of 20-min in fatigued condition compared with the non-fatigued state resulted in a lower decrease in critical power after the fatigue protocol. The results suggest that fatigued condition on power was more evident in shorter efforts and seemed to rely more on a decrease in cadence than on torque.

Validity and Reliability of Two Near-infrared Spectroscopy Devices to Measure Resting Hemoglobin in Elite Cyclists.

A new method to monitor internal training load from muscle oxygen saturation using near-infrared spectroscopy could be of practical application for research and training purposes. This technology has been validated in different scientific fields, including sports science, and Humon Hex and Moxy are two leading brands. However, its relationship with hemoglobin has not been studied. Forty-eight professional cyclists, 19 men and 29 women, underwent a blood test to measure hemoglobin in the early morning. Immediately afterwards, hemoglobin and muscle oxygenation were monitored at rest by Moxy and Humon Hex on their right quadriceps (where the skinfold was measured). Venous blood hemoglobin was higher than the measurement for both devices (p<0.001). Both hemoglobin (p<0.001) and muscle oxygen saturation measurements (p<0.05) were higher in Humon Hex than for Moxy, and there was a reasonable reproducibility (ICC=0.35 for hemoglobin and 0.26 for muscle oxygen saturation). Skinfold had an inverse relationship with hemoglobin measurement (r=-0.85 p<0.001 for Humon Hex and r=-0.75 p<0.001 for Moxy). These findings suggest that resting hemoglobin data provided by these devices are not coincident with those of blood sample, and skinfold has an inverse relationship with blood hemoglobin measurement.