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 (DeltaSmO2min) 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 DeltaSmO2min 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 (VO2peak), and DeltaSmO2min. 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 DeltaSmO2min 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 DeltaSmO2min, with no effect for VO2peak and DeltaSmO2min. 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.
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