Effect of physical activity on long COVID fatigue: an unsolved enigma.

Covid-19 disease is well documented and often the most common symptoms include myalgia and muscle fatigue. Approximately 10% of those infected complain of persistent fatigue even many months after the end of the acute phase of the disease. This gives rise to a condition different from the previous one and commonly known as 'post-acute COVID-19 syndrome' or simply Long-COVID. Although the origin of muscle fatigue is multifactorial, the state of prolonged fatigue observed in the Long-COVID syndrome suggests the existence of a possible state of atrophy or rather acute sarcopenia. Under these conditions, the use of physical activity programs can effectively counteract the state of atrophy underlying the fatigue phenomena observed. If this is also the situation during the Long-COVID, the muscular symptom should be positively influenced by the administration of programmed physical activity cycles. In fact, in patients with Long-COVID, the few published papers seem to indicate that patients who are physically active and who make an effort to engage in physical activity even during the illness have decreased duration and intensity of the illness. However, analysis of the studies in the literature also suggests that a small percentage of people with Long-COVID do not appear to benefit from the application of physical activity programs, so further studies on homogeneous samples are needed to provide a firm answer to the question: can planned physical activity help patients during the pathological course of Long-COVID?

Comments on: Effect of physical activity on long COVID fatigue.

The authors of the Comments on: Effect of physical activity on long COVID fatigue by Daungsupawong F. and Wiwanitkit V. (2023) have highlighted certain aspects of future research that need to be considered before any conclusions can be drawn regarding the effect of previous physical activity and/or fitness on the course of long-COVID. We can only agree with this need, although we hope that the effects of SARS-CoV-2 infection will become less and less burdensome to manage. As we hypothesise in the last part of the article by Coscia et al. (2023), we think it is crucial to identify the molecular mechanism underlying the atrophic effect (if any) of the described disease states, which could originate from a local inflammatory storm induced by Spike binding to the ACE-2 receptor in muscle. When studies on muscle from patients will be available in sufficient numbers, we will be able to try to answer the still open questions.

Physical Activity Effects on Muscle Fatigue in Sport in Active Adults with Long COVID-19: An Observational Study.

Long COVID-19-related changes in physiology includes alterations in performing muscle work as fatigue. Data available do not allow us to define the usefulness of physical activity to attenuate long COVID-19 functional modifications. The present observational study investigates the effects of physical activity on the perception of fatigue, maximum power output, sleep, and cognitive modifications in subjects affected by long COVID-19, distinguishing between active and sedentary subjects. The data demonstrated the following: the perception of fatigue 1 year after the end of virus positivity was significantly reduced with respect to that observed after 6 months by more than 50% more in active subjects compared to sedentary ones; 6 months after the end of virus positivity, the force developed by active subjects was reduced (RM factor: p < 0.001, η2p = 0.527, post hoc: p < 0.001), but the reduction was more pronounced in sedentary ones (mean difference = 38.499 W); poor sleep quality and mild cognitive impairment were assessed in both active and sedentary subjects. In conclusion, the study suggests that the long COVID-19 fatigue was lower in active subjects respect to sedentary ones. A comparative analysis performed due to the overlap of functional alterations between long COVID-19 and ME/CFS showed that in a small percentage of the enrolled subjects (8%), the symptomatology reflected that of ME/CFS and was independent of the individual physical capacities.

Biological Aspects of Selected Myokines in Skeletal Muscle: Focus on Aging.

In the last decade, clear evidence has emerged that the cellular components of skeletal muscle are important sites for the release of proteins and peptides called "myokines", suggesting that skeletal muscle plays the role of a secretory organ. After their secretion by muscles, these factors serve many biological functions, including the exertion of complex autocrine, paracrine and/or endocrine effects. In sum, myokines affect complex multi-organ processes, such as skeletal muscle trophism, metabolism, angiogenesis and immunological response to different physiological (physical activity, aging, etc.) or pathological states (cachexia, dysmetabolic conditions, chronic inflammation, etc.). The aim of this review is to describe in detail a number of myokines that are, to varying degrees, involved in skeletal muscle aging processes and belong to the group of proteins present in the functional environment surrounding the muscle cell known as the "Niche". The particular myokines described are those that, acting both from within the cell and in an autocrine manner, have a defined relationship with the modulation of oxidative stress in muscle cells (mature or stem) involved in the regulatory (metabolic or regenerative) processes of muscle aging. Myostatin, IGF-1, NGF, S100 and irisin are examples of specific myokines that have peculiar features in their mechanisms of action. In particular, the potential role of one of the most recently characterized myokines-irisin, directly linked to an active lifestyle-in reducing if not reversing senescence-induced oxidative damage is discussed in terms of its possible application as an agent able to counteract the deleterious effects of muscle aging.

Sport medicine and safety at work.

As humans become more and more sedentary, physical capacities also become lost along with aerobic fitness, muscular strength, coordination, and action-reaction time. This situation can lead to not only absence from work (back pain is the most common reason in European Union (EU), but especially, workplace accidents. In this article, we want to combine our experience with exercise physiology and physical capacities with our medical work in a critical environment. We tested over ten years, the fitness profile of 1200 Italian Alpine Soldiers, and gave them a scientific training program. We obtained a trained and homogeneous team (homogeneous, in terms of aerobic and anaerobic fitness). Here, we detail changes to aerobic and anaerobic fitness resulting because of soldiers' participation in a training program. We consider this method necessary for safe work in a critical environment.

Effects of a vibrational proprioceptive stimulation on recovery phase after maximal incremental cycle test.

Global Proprioceptive Resonance (GPR) is a recently developed approach conceived to solicit the various cutaneous mechanoreceptors, through application of mechanical multifocal vibration at low amplitude and at definite body sites, limiting the stimulation of the profound structures. This interventional study evaluated the effects of GPR on cardiorespiratory function during the post-exertional recovery period. A group of volunteers involved in Triathlon (a multisport discipline consisting of sequential swim, cycle, and run disciplines higly demanding in terms of metabolic engagment), underwent two maximal incremental exercise tests until exhaustion followed alternatively to (a) a 13 minutes section of GPR or (b) a standard low intensity exercise acute trend of the same duration. These effects of these two approaches were compared in terms of recovery of: heart rate (HR), respiratory rate (RR), peripheral oxygen saturation (SpO2) and venous lactate concentration (Lac). The physiological parameters (HR, RR, SpO2 and Lac) recorded in the pre-exertion session showed similar values between the 40 volunteers while several differences were recorded in the post-exertion phase. After 6 min of GPR recovery it was recorded a drop in RR below baseline (19.4±4.15 min-1 vs. 12.2± 0.4 min-1; p<0.001) coupled with an increase in peripheral oxygen saturation above the baseline (GPR: 99.0%±0.16% vs. 96.6%±0.77%, p<0.001). Moreover, the most striking result was the drop in lactate concentration measured after 13 min of GPR recovery: 84.5±3.5% in GPR vs 2.9±7.6% reduction in standard recovery (p<0.001). Notably no differences were recorded recovery of heart rate. GPR has promising effects on post-exercise recovery on RR, SpO2 and lactate level on young athletes.

Effects of a vibrational proprioceptive stimulation on recovery phase after maximal incremental cycle test.

Global Proprioceptive Resonance (GPR) is a recently developed approach conceived to solicit the various cutaneous mechanoreceptors, through application of mechanical multifocal vibration at low amplitude and at definite body sites, limiting the stimulation of the profound structures. This interventional study evaluated the effects of GPR on cardiorespiratory function during the post-exertional recovery period. A group of volunteers involved in Triathlon (a multisport discipline consisting of sequential swim, cycle, and run disciplines higly demanding in terms of metabolic engagment), underwent two maximal incremental exercise tests until exhaustion followed alternatively to (a) a 13 minutes section of GPR or (b) a standard low intensity exercise acute trend of the same duration. These effects of these two approaches were compared in terms of recovery of: heart rate (HR), respiratory rate (RR), peripheral oxygen saturation (SpO2) and venous lactate concentration (Lac). The physiological parameters (HR, RR, SpO2 and Lac) recorded in the pre-exertion session showed similar values between the 40 volunteers while several differences were recorded in the post-exertion phase. After 6 min of GPR recovery it was recorded a drop in RR below baseline (19.4±4.15 min-1 vs. 12.2± 0.4 min-1; p<0.001) coupled with an increase in peripheral oxygen saturation above the baseline (GPR: 99.0%±0.16% vs. 96.6%±0.77%, p<0.001). Moreover, the most striking result was the drop in lactate concentration measured after 13 min of GPR recovery: 84.5±3.5% in GPR vs 2.9±7.6% reduction in standard recovery (p<0.001). Notably no differences were recorded recovery of heart rate. GPR has promising effects on post-exercise recovery on RR, SpO2 and lactate level on young athletes.

Old muscle in young body: an aphorism describing the Chronic Fatigue Syndrome.

The chronic fatigue syndrome (CFS) otherwise known as myalgic encephalomyelitis (ME), is a debilitating syndrome whose identification is very complex due to lack of precise diagnostic criteria. This pathology begins with limitations in duration and intensity of exercise and rapid onset of pain during physical activity. Its etiology is unknown, and symptoms are not limited to the muscles. Epidemiology is rather difficult to delimit, even if it affects mainly young (20-40 years), female subjects. The results of muscular research show some peculiarities that can justify what has been observed in vivo. In particular, 1. presence of oxidative damage of lipid component of biological membranes and DNA not compensated by the increase of the scavenger activity; 2. Excitation-Contraction (E-C) alteration with modification of Ca2+ transport; 3. passage from slow to fast fiber phenotype; 4. inability to increase glucose uptake; 5. presence of mitochondrial dysfunction; and 6. genes expressed differentially (particularly those involved in energy production). The skeletal muscles of CFS / ME patients show a significant alteration of the oxidative balance due to mitochondrial alteration and of the fiber phenotype composition as shown in sarcopenic muscles of the elderly. Vice versa, the muscle catabolism does not appear to be involved in the onset of this syndrome. The data support the hypothesis that patients with CFS are subjected to some of the problems typical for muscle aging, which is probably related to disorders of muscle protein synthesis and biogenesis of mitochondria. Patients with CFS can benefit from an appropriate training program because no evidence suggests that physical exercise worsens symptoms. Type, intensity and duration of any physical activity that activates muscle contraction (including Electrical Stimulation) require further investigation even if it is known that non-exhaustive physical activity decreases painful symptomatology.