The effects of endurance training on muscle oxygen desaturation during incremental exercise tests: a systematic review and meta-analysis.

Objective: Minimum muscle oxygen saturation (SmO₂min) measured via near-infrared spectroscopy (NIRS) is a common measure during incremental exercise testing (IET). Our objective was to determine the effects of pre-to-post endurance training on SmO₂min (ΔSmO₂min) during an IET, using a meta-analysis.

Data sources: MEDLINE, EMBASE, and SPORTDiscus.

Study selection: Studies including healthy individuals had to meet the following criteria: (1) endurance training intervention; (2) peripheral muscle NIRS; (3) incremental exercise test pre/post training; (4) SmO₂ or analogous saturation parameter measured.

Analysis: A PEDro scale was used for risk of bias analysis. A random effect meta-analysis model was used to synthesize the effect of training on ΔSmO₂min in individual studies. Statistical heterogeneity was quantified using I² statistic. A meta-regression was used to estimate the effect of training on the relationship between peak cycling power output (Wpeak), peak pulmonary oxygen uptake (V˙O₂peak), and ΔSmO₂min. A mixed-effect model was used to estimate categorical variables.

Results: Five studies met the inclusion criteria. No difference in SmO₂min was detected following training pre- and post-intervention IETs. A trend for an effect of training on the relationship between Wpeak and ΔSmO₂min was observed (p = 0.06).

Conclusion: This meta-analysis showed no effects of endurance training on SmO₂min during an IET. Our results showed a trend for an effect of training on the relationship between Wpeak and ΔSmO₂min, with no effect for V˙O₂peak and ΔSmO₂min. It is possible that SmO₂min is not affected by endurance training, and may be used as a physiological marker for improvements in submaximal performance rather than at peak.