The single stranded RNA virus SARS-CoV-2 has caused a massive addition to the already leading global cause of mortality, viral respiratory tract infections. Characterized by and associated with early and deleteriously enhanced production of pro-inflammatory cytokines by respiratory epithelial cells, severe COVID-19 illness has the potential to inflict acute respiratory distress syndrome and even death. Due to the fast spreading nature of COVID-19 and the current lack of a vaccine or specific pharmaceutical treatments, understanding of viral pathogenesis, behavioral prophylaxis, and mitigation tactics are of great public health concern. This review article outlines the immune response to viral pathogens, and due to the novelty of COVID-19 and the large body of evidence suggesting the respiratory and immune benefits from regular moderate intensity exercise, provides observational and mechanistic evidence from research on other viral infections that suggests strategically planned exercise regimens may help reduce susceptibility to infection, while also mitigating severe immune responses to infection commonly associated with poor COVID-19 prognosis. We propose that regular moderate intensity exercise should be considered as part of a combinatorial approach including widespread hygiene initiatives, properly planned and well-executed social distancing policies, and use of efficacious facial coverings like N95 respirators. Studies discerning COVID-19 pathogenesis mechanisms, transfer dynamics, and individual responses to pharmaceutical and adjunct treatments are needed to reduce viral transmission and bring an end to the COVID-19 pandemic.
Broadly accepted is that most knee injuries result from increased vertical forces, usually induced by an incidental ski fall, collision, or a high jump. We present a new non-contact knee injury mechanism that can happen during a ski turn. Such an injury is governed by a sudden inward turn of the inner ski and consequent swing of the inner leg followed by a nearly instant stop when locked by hip and knee joints. The model provides predictive results for a lateral tibial plateau compression fracture because several simplifications have been made. We confirmed that the modelled compression stresses at typical skiing conditions and with typical skiing equipment can provoke serious knee injuries. The awareness of skiers and skiing equipment industry of the described knee injury mechanism can act as an important injury-prevention factor.
Exercise training (ET) has been reported to reduce oxidative stress and endoplasmic reticulum (ER) stress in the heart following myocardial infarction (MI). Thioredoxin 1 (Trx1) plays a protective role in the infarcted heart. However, whether Trx1 regulates ER stress of the infarcted heart and participates in ET-induced cardiac protective effects are still not well known. In this work, H9c2 cells were treated with hydrogen peroxide (H2O2) and recombinant human Trx1 protein (TXN), meanwhile, adult male C57B6L mice were used to establish the MI model, and subjected to a six-week aerobic exercise training (AET) with or without the injection of Trx1 inhibitor, PX-12. Results showed that H2O2 significantly increased reactive oxygen species (ROS) level and the expression of TXNIP, CHOP and cleaved caspase12, induced cell apoptosis; TXN intervention reduced ROS level and the expression of CHOP and cleaved caspase12, and inhibited cell apoptosis in H2O2-treated H9c2 cells. Furthermore, AET up-regulated endogenous Trx1 protein expression and down-regulated TXNIP expression, restored ROS level and the expression of ER stress-related proteins, inhibited cell apoptosis as well as improved cardiac fibrosis and heart function in mice after MI. PX-12 partly inhibited the AET-induced beneficial effects in the infarcted heart. This study demonstrates that Trx1 attenuates ER stress-induced cell apoptosis, and AET reduces MI-induced ROS overproduction, ER stress and cell apoptosis partly through up-regulating of Trx1 expression in mice with MI.
We compared the effects of low intensity concentric (CON) and eccentric (ECC) exercise on the force and neural responses of the dominant (exercised) elbow flexors (EFs), and studied if these conditions could induce cross-over effects to the contralateral (non-exercised) EFs. Fifteen subjects (8 males) completed all conditions (CON and ECC: 6 sets of low intensity exercise to failure; control: rest) in separate visits with a randomized order. Maximal isometric force and electromyography (EMG) of the dominant and contralateral EFs were assessed at pre, immediate-, 24-, and 48-h-post. Two-factor (condition and time) linear mixed-model analyses were performed to examine the force and EMG responses. Immediately post CON, contralateral EFs force was significantly (p = 0.026) higher (12.41%) than control, but no cross-over effects regarding the neural responses were observed. Immediately post ECC, dominant EFs force was significantly lower in ECC, compared to CON (p = 0.003) and control (p < 0.001). This force remained depressed at 24- and 48-h post ECC, when compared to CON (p < 0.001) and control (p < 0.001). Our data suggests that submaximal unilateral exercises are not likely to impair contralateral muscle strength performance. Instead, concentric exercises may acutely improve muscle strength for the contralateral limb. However, this effect is not explained by changes in muscle excitation.
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Conclusion
We tested a PEEP (4.2 cmH2O) mouthpiece (PMP) on maximal cycling performance in healthy adults. Experiment-1, PMP vs. non-PMP mouthpiece (CON) [n= 9 (5♂), Age = 30 ± 2 yr]; Experiment-2, PMP vs. no mouthpiece (NMP) [n = 10 (7♂), Age = 27 ± 1 yr]. At timepoint 1 in both experiments (mouthpiece condition randomized) subjects performed graded cycling testing (GXT) (Corival® cycle ergometer) to determine V˙O2peak (ml∗kg∗min−1), O2pulse (mlO2∗bt−1), GXT endurance time (GXT-T(s)), and V˙O2(ml∗kg∗min−1)-at-ventilatory-threshold (V˙O2 @VT). At timepoint 2 72 h later, subjects completed a ventilatory-threshold-endurance-ride [VTER(s)] timed to exhaustion at V˙O2 @VT power (W). One week later at timepoints 3 and 4 (time-of-day controlled), subjects repeated testing protocols under the alternate mouthpiece condition. Selected results (paired T-test, p<0.05): Experiment 1 PMP vs. CON, respectively: V˙O2peak = 45.2 ± 2.4 vs. 42.4 ± 2.3 p<0.05; V˙O2@VT = 33.7 ± 2.0 vs. 32.3 ± 1.6; GXT-TTE = 521.7 ± 73.4 vs. 495.3 ± 72.8 (p<0.05); VTER = 846.2 ± 166.0 vs. 743.1 ± 124.7; O2pulse = 24.5 ± 1.4 vs. 23.1 ± 1.3 (p<0.05). Experiment 2 PMP vs. NMP, respectively: V˙O2peak = 43.3 ± 1.6 vs. 41.7 ± 1.6 (p<0.05); V˙O2@VT = 31.1 ± 1.2 vs. 29.1 ± 1.3 (p<0.05); GXT-TTE = 511.7 ± 49.6 vs. 486.4 ± 49.6 (p<0.05); VTER 872.4 ± 134.0 vs. 792.9 ± 122.4; O2pulse = 24.1 ± 0.9 vs. 23.4 ± 0.9 (p<0.05). Results demonstrate that the PMP conferred a significant performance benefit to cyclists completing high intensity cycling exercise.
To evaluate changes achieved in whole-body and regional (upper limbs, lower limbs, and trunk) estimates of body composition, twenty professional male soccer players (7 defenders, 7 midfielders, 6 forwards) underwent dual-energy x-ray absorptiometry (DXA) analysis at the beginning and end of pre-season. Measures included: mass, fat mass (FM), fat-free mass (FFM), and body fat per cent (BF%). Players’ activity during on-field training sessions was monitored using Global Positioning System (GPS) units, with GPS data used to obtain estimations of energy expenditure (EE). Whole-body mass remained unchanged across the pre-season. Moderate significant increases and decreases were achieved in whole-body FFM (Pre: 59.58 ± 5.27 kg; Post: 60.61 ± 5.18 kg; p = 0.001; d = 0.87) and FM (Pre: 10.60 ± 1.88 kg; Post: 9.56 ± 1.81 kg; p = 0.001; d = 0.85), respectively. Moderate significant decreases were achieved in whole-body BF% (Pre: 14.4 ± 2.3%; Post: 12.9 ± 2.0%; p < 0.001; d = 0.94). No significant inter-positional differences were observed for the changes achieved in any global or regional estimate of body composition. Total EE was significantly correlated with ΔFM (r = 0.65, p = 0.002), ΔFFM (r = 0.46, p = 0.03), and ΔBF% (r = 0.67, p = 0.002). The total EE of pre-season training accounted for 42%, 21%, and 45% of the variance in ΔFM, ΔFFM, and ΔBF%, respectively. These findings suggest that the pre-season period is a suitable time for initiating favourable alterations in body composition following the off-season in elite soccer players.
COVID-19 patients are susceptible to hypercoagulability. For the safe return to sports after COVID-19, athletes or individuals wanting to resume physical activity should complete screening for myocardial injury and myocarditis. In addition, patients with COVID-19 are reported at prevalence of 27%-31% for venous thromboembolic events. The probability of deep vein thrombosis and pulmonary embolism prior to intensive exercise after COVID-19 infection should be considered. The prevalence of cardiac injury is reported at 19%, and the prevalence of deep vein thrombosis and pulmonary embolism is higher than that for myocarditis. Thus, the heart is not the only system needing screened. Examination for myocardial injury and myocarditis are mandatory. Also, deep vein thrombosis, and pulmonary thromboembolism must be considered, and when possible, blood troponin values, D-dimer prothrombin time, and activated partial thromboplastin time levels are determined for COVID-19 infection athletes or any individual before returning to sporting practice or intense physical activity or exercise.