Millions of people worldwide are infected with COVID-19, and COVID-19 survivors have been found to suffer from functional disabilities and mental disorders such as depression and anxiety. This is a matter of concern because COVID-19 is still not over. Because reinfection is still possible in COVID-19 survivors, decreased physical function and increased stress and anxiety can lower immune function. However, the optimal exercise intensity and volume appear to remain unknown. Therefore, the current systematic review aimed to evaluate the effect of resistance or aerobic exercises in post-COVID-19 patients after hospital discharge. We conducted searches in the Scopus, SciELO, PubMed, Web of Science, Science Direct, and Google Scholar databases. Studies that met the following criteria were included: (i) English language, (ii) patients with COVID-19 involved with resistance or aerobic exercise programs after hospital discharge. Out of 381 studies reviewed, seven studies met the inclusion criteria. Evidence shows that exercise programs composed of resistance exercise (e.g., 1–2 sets of 8–10 repetitions at 30–80% of 1RM) along with aerobic exercise (e.g., 5 to 30 min at moderate intensity) may improve the functional capacity and quality of life (reduce stress and mental disorders) in post-COVID-19 patients. In addition, only one study reported reinfection of three subjects involved with the exercise program, suggesting that exercise programs may be feasible for the rehabilitation of the patients. A meta-analysis was not conducted because the included studies have methodological heterogeneities, and they did not examine a control group. Consequently, the results should be generalized with caution.

In order to verify the effects of heat and exercise acclimation (HA) on resting and exercise-induced expression of plasma and leukocyte heat shock protein 72 (Hsp72) in humans, nine healthy young male volunteers (25.0 ± 0.7 years; 80.5 ± 2.0 kg; 180 ± 2 cm, mean ± SE) exercised for 60 min in a hot, dry environment (40 ± 0°C and 45 ± 0% relative humidity) for 11 days. The protocol consisted of running on a treadmill using a controlled hyperthermia technique in which the work rate was adjusted to elevate the rectal temperature by 1°C in 30 min and maintain it elevated for another 30 min. Before and after the HA, the volunteers performed a heat stress test (HST) at 50% of their individual maximal power output for 90 min in the same environment. Blood was drawn before (REST), immediately after (POST) and 1 h after (1 h POST) HST, and plasma and leukocytes were separated and stored. Subjects showed expected adaptations to HA: reduced exercise rectal and mean skin temperatures and heart rate, and augmented sweat rate and exercise tolerance. In HST1, plasma Hsp72 increased from REST to POST and then returned to resting values 1 h POST (REST: 1.11 ± 0.07, POST: 1.48 ± 0.10, 1 h POST: 1.22 ± 0.11 ng mL⁻¹; p < 0.05). In HST2, there was no change in plasma Hsp72 (REST: 0.94 ± 0.08, POST: 1.20 ± 0.15, 1 h POST: 1.17 ± 0.16 ng mL⁻¹; p > 0.05). HA increased resting levels of intracellular Hsp72 (HST1: 1 ± 0.02 and HST2: 4.2 ± 1.2 density units, p < 0.05). Exercise-induced increased intracellular Hsp72 expression was observed on HST1 (HST1: REST, 1 ± 0.02 vs. POST, 2.9 ± 0.9 density units, mean ± SE, p < 0.05) but was inhibited on HST2 (HST2: REST, 4.2 ± 1.2 vs. POST, 4.4 ± 1.1 density units, p > 0.05). Regression analysis showed that the lower the pre-exercise expression of intracellular Hsp72, the higher the exercise-induced increase (R = −0.85, p < 0.05). In conclusion, HA increased resting leukocyte Hsp72 levels and inhibited exercise-induced expression. This intracellular adaptation probably induces thermotolerance. In addition, the non-increase in plasma Hsp72 after HA may be related to lower stress at the cellular level in the acclimated individuals.

The aim of this study was to investigate the effects of multiple cold-water immersions (CWIs) on muscle function, markers of muscle damage, systemic inflammation and ECM degradation following exercise-induced muscle damage (EIMD). Thirty physically active males were randomly assigned to either a control (n = 15) or cold-water immersion (CWI) group (n = 15). The CWI group performed one immersion (10 °C for 20 min) at post-exercise and every 24 h for the following 72 h, while the control group remained in a seated position during these corresponding periods. Muscle strength, vertical jump height, muscle thickness, delayed-onset muscle soreness (DOMS), systemic creatine kinase (CK), C-reactive protein (CRP), inflammatory cytokines and matrix metalloproteinase-2 (MMP-2) activity were assessed at Pre, Post, 24, 48, 72, 96 and 168 h following EIMD. No significant time × group interaction was obtained for muscle strength, vertical jump height recovery and MMP-2 activity (p > 0.05). At 24 h, muscle thickness from the CWI group returned to baseline and was lower than the control (p = 0.04). DOMS returned to baseline at 168 h for the CWI group (p = 0.109) but not for the control (p = 0.008). At 168 h, CK showed a time-group difference with a greater peak for the control group (p = 0.016). In conclusion, multiple CWIs attenuated muscle damage, but not altered systemic inflammation and muscle function recovery.

The study aimed to evaluate the effects of chemotherapy treatment on muscle strength, quality of life, fatigue, and anxiety in women with breast cancer. Nineteen women who were undergoing a chemotherapy treatment (breast cancer treatment [BCT] group, 52.2 ± 13.1 years) and 18 women without cancer (control [CNT] group, 55.8 ± 8.4 years) answered questionnaires for evaluation of fatigue (Fatigue Scale), quality of life (Short-Form Healthy Survey [SF-36] questionnaire), and anxiety (State-Trait Anxiety Inventory [IDATE]) levels. Muscle strength was also assessed by an isometric grip test and an isokinetic knee extension test. Physical limitations, social and emotional domains of quality of life were lower in the BCT group in comparison to the CNT group (p = 0.002; p = 0.003; p = 0.0003, respectively). The other domains did not differ between groups (p > 0.05). There were no differences in fatigue and anxiety levels between both the BCT and CNT groups (p > 0.05). Additionally, isometric grip strength was higher in the CNT group when compared to the BCT group (p = 0.048). However, there were no differences between the BCT and CNT groups for peak torque and total work at both 60°.s⁻¹ (p = 0.95 and p = 0.61, respectively) and 180°.s⁻¹ (p = 0.94 and p = 0.72, respectively). These results suggest that three cycles of chemotherapy treatment may impair handgrip isometric strength and quality of life in women with breast cancer.

To compare the effects of high-load, low-repetition maximum (LRM) and low-load, high-repetition maximum (HRM) resistance training regimens on muscular fitness in untrained adolescents. Forty-five untrained adolescents of both sexes (13.7±0.8 years; 161.3±7.5 cm, 56.8±13.4 kg) were randomly assigned into one of three groups: 1) LRM (n = 17): volunteers performed three sets of 4-6-repetition maximum (RM); 2) HRM (n = 16): volunteers performed three sets of 12–15 RM; and 3) control (CON, n = 12). Training was performed two times a week for 9 weeks. After training, there were significant increases in 1 RM chest press (LRM = 14.8% and HRM = 14.2%, p<0.05) and squat (LRM = 26.4% and HRM = 25.7%, p0.05). Additionally, muscular endurance increased significantly for the chest press (LRM = 14.5% and HRM = 21.8%, p<0.05) and squat test (LRM = 31.4% and HRM = 32.4%, p0.05). These results suggest that both high-load, low-repetition and moderate-load, high-repetition resistance training can be prescribed to improve muscular fitness in untrained adolescents.