DISCUSSION
hypoxia, musculoskeletal PASC, LE musculoskeletal PASC, muscle perfusion impairment
HYPOXIA, HANSEN
This study investigated the efficacy of daily self‐administered E‐Stim in promoting LE muscle recovery and improving muscle perfusion and endurance in individuals with LE musculoskeletal PASC. This study utilized NIRS and sEMG assessments and found that after a 4 week intervention period of daily 1 h E‐Stim sessions, participants demonstrated a significant increase in both muscle perfusion and endurance. The findings of this study suggest that self‐administered E‐Stim is a safe and effective therapeutic option for individuals with LE musculoskeletal PASC seeking to improve muscle recovery.During dynamic muscle‐stress (e.g., exercise), NIRS signals from the muscle tissue reflect myoglobin (Mb) (Bendahan et al., In healthy individuals, muscle tissue typically shows an immediate recovery of oxygen levels after cessation of exercise‐induced stress (healthy HR2S) (Barron et al., One important consideration is the heterogeneous composition of slow‐ and fast‐twitch fibers in the GNM, which have different oxygen metabolizing capabilities dependent on their levels of Mb and mitochondria (Edgerton et al., The evidence on post‐COVID‐19 exercise‐induced hypoxia in previously hospitalized patients is compelling. A recent cohort study of 26 hospitalized patients found a 50% incidence of hypoxia during a 6 min walking test prior to discharge (Fuglebjerg et al., To investigate the possible role of peripheral oxygen as a marker of muscle perfusion impairment or improvement in individuals with musculoskeletal PASC, we reexamined HR2S at 4 weeks for both groups. Consistent with previous findings (Hansen et al., An additional objective measure to assess the improvement in muscle endurance is through iEMG analysis (Zulbaran‐Rojas et al., Recent studies suggest that endurance training may lead to an increase in capillary density (Hirai et al., While this study used NIRS imaging of the plantar foot muscles rather than the gastrocnemius, it is important to note that this design does not necessarily introduce a confounding factor. Many exercises that involve the calf muscle, such as running, cycling, and calf raises, also involve muscular contribution from the foot muscles. However, since E‐Stim precludes muscular contributions outside the gastrocnemius, it is reasonable to assume that most changes observed pre‐ versus post‐E‐Stim therapy are attributable to the gastrocnemius itself. Nonetheless, it should be acknowledged that a limitation of this study is the lack of NIRS imaging specifically targeting the gastrocnemius muscle.