RESUMEN
OBJECTIVES: Neuromuscular efficiency (NME) is impaired in fibromyalgia (FM). Hyperbaric oxygen therapy (HBOT) is a medical treatment using 100% of oxygen through an oxygen mask. HBOT in FM induces changes in cortical excitability and a secondary reduction in pain and muscle fatigue. However, there are still no direct data indicating changes in muscle fatigue. The aim of this study was to assess whether the reduction in muscle fatigue so far attributed to a central effect of HBOT can be directly detected by means of non-invasive sEMG as a change in NME. METHODS: The study was an observational longitudinal study on changes in NME induced by 20 sessions of HBOT at 2.4 atmosphere, in 22 patients with FM (3M; 19F) (age 49.8±9.5; height 164.7±7.5; weight 63.8±12.7). sEMG was recorded in single differential configuration from the biceps brachii muscle during the 30-second fatiguing contractions using linear arrays of eight adhesive electrodes. RESULTS: Evaluations made before and immediately after the first session showed that maximal strength did not change (T0 49±20 N, T1 49±19 N, p=0.792), thus suggesting that HBOT did not induce muscle fatigue or potentiation. After 20 sessions of HBOT, NME increased from 1.6±1.1 to 2.1±0.8 (p=0.050), whereas maximal strength, EMG amplitude and muscle fibre CV did not change. CONCLUSIONS: HBOT did not improve muscle strength or change muscle fibre content, but improved the ability of the central motor command to generate the same effort (MVC) with fewer recruited fibres. Our sEMG findings underlined a modified central mechanism related to fibre type recruitment order, thus suggesting that muscle fatigue is not primarily a muscular problem, as also demonstrated by other authors with different methods.