Comparative Bilateral Measurements of Vastus Lateralis Muscle Oxygen Desaturation Kinetics during 30 S Sprint Cycling Exercise: Effects of Age and Performance

Abstract

The study assessed vastus lateralis oxygen desaturation kinetics (SmO₂) in 32 male cyclists (16 Seniors, 16 Juniors) during a 30 s sprint, examining effects of age and performance. An incremental test was used to determine ventilatory thresholds (VT1, VT2) and maximal oxygen uptake (VO_2kg), followed by a sprint test to evaluate anaerobic performance. Cyclists' performance phenotype was determined as the ratio of power at VT2 to 5 s peak sprint power. Juniors exhibited sprinter-like traits, excelling in all functional tests except for lactate levels post-sprint. SmO₂ data showed no age-related or bilateral differences across participants. The combined mean response time (MRT) revealed stronger bilateral goodness of fit (R² = 0.64) than individual time delay (TD) and time constant (τ). Higher VO_2kg at VT2, peak power, and maximal uptake were linked to longer TD, while shorter TD correlated with higher lactate production and increased fatigue. Bilaterally averaged SmO₂ kinetics distinguished between sprint and endurance athletes, indicating the potential to reflect the alactic anaerobic system's capacity and depletion. Age did not affect desaturation rates, but younger cyclists showed greater response amplitude, attributed to a higher initial baseline rather than maximal desaturation at the end of the exercise.

Keywords: Moxy Monitor; NIRS; anaerobic capacity; phosphocreatine.

Figure 1

Illustration of 30 s sprint effort and measured and calculated parameters. Baseline (BL), time to achieve peak power (t@Pmax), maximal average 5 s power (Pmax5s), minimal average 5 s power (Pmin5s), baseline power (P_BL), time delay (TD), time constant (τ), mean response time (MRT), minimal oxygen saturation value (End SmO₂), amplitude (A_p), oxygen saturation (SmO₂).

Figure 2

Bilateral power dynamics of non-dominant (ND) (open symbols) and dominant (DO) (closed symbols) leg during sprinting in Juniors (triangles) and Seniors (circles) age groups. Maximal average 30 s power (Pmax30s); power drop (PD); fatigue index (FI). *—significant difference between Juniors and Seniors; (p < 0.05; d > 0.2); #—significant difference between DO and ND leg; (p < 0.05; d > 0.2).

Figure 3

Bilateral agreement between time variables of SmO₂ kinetics during 30 s sprint cycling. Non-dominant leg (ND), dominant leg (DO), time delay (TD) (A), time constant (τ) (B), mean response time (MRT) (C).

Figure 4

Bilateral agreement between SmO₂ amplitude variables of SmO₂ kinetics during 30 s sprint cycling. Non-dominant leg (ND), dominant leg (DO), baseline (BL) (A), minimal oxygen saturation value (End SmO₂) (B), amplitude (A_p) (C).

Figure 5

Relationship of fatigue measures and time variables of SmO₂ kinetics across all participants, considering both dominant (DO) and non-dominant (ND) legs: Fatigue index (FI) and time delay (TD) (A), time constant (τ) (B), mean response time (MRT) (C).