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Dear Editor-in-ChiefThe world has recently experienced one of the hardest pandemics, COVID-19. Clinical signs of this disease include fever, dry cough, and diarrhea, or different symptoms that lead to acute respiratory distress syndrome with a further increase in the severity of the disease. Although the first observations of this disease are the involvement of symptoms and respiratory and heart injuries, various studies have also shown the nerve damage caused by this disease. Common neurological symptoms include headache, dizziness, anosmia, seizures, or paralysis. The elderly and critically ill are in the high-risk group and have shown severe neurological symptoms after COVID-19. Apart from COVID-19-induced cellular and neurological damage, this disease has a profound effect on the mental health of people around the world. Increasing the duration of this disease and staying at home causes social and economic problems and as a result mental health problems (Verma et al., 2020). Neurological and mental illnesses are very common all over the world.Psychological resilience was an important issue during COVID-19 epidemic. In other words, during an epidemic, mental health of people should be consider and cheeked, and entertainment programs should be prevented from causing psychological damage. Research during the COVID-19 epidemic found that because of the psychological pressures to increase psychological resilience, people tended to be more exposed to the outdoors, exercise more, receive more social support from family, friends and important people, sleep better, and pray more, that these factors were effective in mitigating psychological trauma. In most studies, spiritual health affects mental health, because repeated prayers and worships have been more independently associated with psychological resilience (Killgore et al., 2020). In other words, those who actively participate in these spiritual activities and strengthen their relationship with God are found to have the most psychological resilience to the mental health challenges imposed by COVID-19. In addition, the effects of exercise at the cellular level can help improve memory and psyche and be effective in improving psychological resilience. To date, no studies have been performed on secretions due to muscle contraction and its effect on the brain and psychological function, and psychological resilience especially to control the psychological damage caused by an epidemic.Exercise has many beneficial effects on brain health and helps reduce the risks of dementia, depression, and stress, and is involved in restoring and maintaining cognitive function and metabolic control. The fact that exercise is sensed by the brain suggests that environmental factors induced by the muscle allow a direct link between muscle function and the brain. Muscles secrete myokines that help regulate hippocampal function. Evidence is accumulating that myokine cathepsin B crosses the blood-brain barrier to increase brain-derived neurotrophic factor production, resulting in neurogenesis, memory, and learning. In addition, the muscle tissue itself can affect the central nervous system, memory, and psyche in form of endocrine by increasing BDNF expression. Exercise also increases the expression of the neurogenic gene FNDC5 (which encodes myogenic FNDC5-dependent PGC1α), which in turn can help increase levels of brain-derived neurotrophic factor (Pedersen, 2019).Serum levels of myokine, IL-6, increase with exercise and may have beneficial effects on the central nervous system. Exercise also increases PGC1α-dependent muscle expression and the enzymes kynurenine aminotransferase, which beneficially alters the balance between the neurotoxic kynurenine and the neuroprotective Kynurenic acid, thereby reducing depressive symptoms. Signaling myokine and other muscle factors and exercise-induced hepatokines and adipokines play a role in the beneficial effects of exercise on neurogenesis, cognitive function, appetite, and metabolism, thus supporting the existence of a muscle-brain endocrine axis. Also, it can affect psychological resilience which needs more studies.

Purpose: The aim was to perform a meta-analysis of studies examining the effects of β-hydroxy-β-methylbutyrate (HMB) supplementation on hormonal adaptations after resistance training. Methods: PubMed, Directory of Open Access Journals, Google Scholar and Web of Science were systematically searched up to June 2021 and updated in July 2022. The Cochrane Collaboration tool for evaluating the risk of bias was applied for assessing the studies' quality and then eight studies were included in the review. The random effects model was applied to estimate the overall effect. Results: The HMB group showed greater adaptive changes in cortisol levels in comparison to placebo (PL) group after resistance training (ES; − 0.2 vs. 0.08, p = 0.041, ∆%; − 2.5 vs. 1.2, p = 0.1). Similarly, the HMB group indicated greater adaptations in testosterone (ES; 0.44 vs. 0.02, p = 0.02, ∆%; 13.4 vs. 3.2, p = 0.02) and IGF-1 (ES; 0.32 vs. 0.13, p = 0.001, ∆%; 3.75 vs. 1.75, p = 0.01) levels after training intervention. There was no significant difference between the HMB and PL groups in growth hormone changes following resistance training (ES; 0.77 vs. 0.2, p = 0.8, ∆%; 55.3 vs. 11.7, p = 0.43). Conclusions: The results of this meta-analysis demonstrated the efficacy of HMB supplementation (3 g daily HMB for 7 weeks) to provide greater changes compared with placebo supplementation in resting hormonal concentrations (i.e., testosterone, cortisol and IGF-1). [ABSTRACT FROM AUTHOR]

B Correction to: Sport Sciences for Health (2023) b https://doi.org/10.1007/s11332-023-01081-9 The last name of the 3rd author has been incorrectly published in the original publication. Correction to: Effects of HMB supplementation on hormonal adaptations following resistance training: a systematic review and meta-analysis The original article can be found online at https://doi.org/10.1007/s11332-023-01081-9. [Extracted from the article]