The coronavirus disease (COVID-19), caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection, is leading to unknown and unusual health conditions that are challenging to manage. Post-COVID-19 syndrome is one of those challenges, having become increasingly common as the pandemic evolves. The latest estimates suggest that 10 to 20% of the SARS-CoV-2 patients who undergo an acute symptomatic phase are experiencing effects of the disease beyond 12 weeks after diagnosis. Although research is beginning to examine this new condition, there are still serious concerns about the diagnostic identification, which limits the best therapeutic approach. Exercise programs and physical activity levels are well-known modulators of the clinical manifestations and prognosis in many chronic diseases. This narrative review summarizes the up-to-date evidence on post-COVID-19 syndrome to contribute to a better knowledge of the disease and explains how regular exercise may improve many of these symptoms and could reduce the long-term effects of COVID-19.

The use of bar velocity to estimate relative load in the back squat exercise was examined. 80 strength-trained men performed a progressive loading test to determine their one-repetition maximum (1RM) and load-velocity relationship. Mean (MV), mean propulsive (MPV) and peak (PV) velocity measures of the concentric phase were analyzed. Both MV and MPV showed a very close relationship to %1RM (R²=0.96), whereas a weaker association (R²=0.79) and larger SEE (0.14 vs. 0.06 m·s⁻¹) were found for PV. Prediction equations to estimate load from velocity were obtained. When dividing the sample into 3 groups of different relative strength (1RM/body mass), no differences were found between groups for the MPV attained against each %1RM. MV attained with the 1RM was 0.32±0.03 m·s⁻¹. The propulsive phase accounted for ~82% of concentric duration at 40% 1RM, and progressively increased until reaching 100% at 1RM. Provided that repetitions are performed at maximal intended velocity, a good estimation of load (%1RM) can be obtained from mean velocity as soon as the first repetition is completed. This finding provides an alternative to the often demanding, time-consuming and interfering 1RM or nRM tests and allows implementing a velocity-based resistance training approach.

Purpose: The aim of the study was to compare the outcomes of patients with post‐COVID‐19 condition undergoing supervised therapeutic exercise intervention or following the self‐management WHO (World Health Organization) rehabilitation leaflet.Methods: A randomized controlled trial was carried out that included 39 participants with post‐COVID‐19 condition who had a chronic symptomatic phase lasting >12 weeks. Comprehensive medical screening, patient‐reported symptoms, and cardiorespiratory fitness and muscular strength were assessed. Patients were randomly assigned to a tailored multicomponent exercise program based on concurrent training for 8 weeks (two supervised sessions per week comprised resistance training combined with aerobic training [moderate intensity variable training], plus a third day of monitored light intensity continuous training), or to a control group which followed the WHO guidelines for rehabilitation after COVID‐19.Results: After follow‐up, there were changes in physical outcomes in both groups, however, the magnitude of the change pre–post intervention favored the exercise group in cardiovascular and strength markers: VO₂max +5.7%, sit‐to‐stand −22.7% and load‐velocity profiles in bench press +6.3%, and half squat +16.9%, (p < 0.05). In addition, exercise intervention resulted in a significantly better quality of life, less fatigue, less depression, and improved functional status, as well as in superior cardiovascular fitness and muscle strength compared to controls (p < 0.05). No adverse events were observed during the training sessions.Conclusion: Compared to current WHO recommendations, a supervised, tailored concurrent training at low and moderate intensity for both resistance and endurance training is a more effective, safe, and well‐tolerated intervention in post‐COVID‐19 conditions.

This study analysed the effect of imposing a pause between the eccentric and concentric phases on the biological within-subject variation of velocity- and power–load isoinertial assessments. Seventeen resistance-trained athletes undertook a progressive loading test in the bench press (BP) and squat (SQ) exercises. Two trials at each load up to the one-repetition maximum (1RM) were performed using 2 techniques executed in random order: with (stop) and without (standard) a 2-s pause between the eccentric and concentric phases of each repetition. The stop technique resulted in a significantly lower coefficient of variation for the whole load–velocity relationship compared to the standard one, in both BP (2.9% vs. 4.1%; P = 0.02) and SQ (2.9% vs. 3.9%; P = 0.01). Test–retest intraclass correlation coefficients (ICCs) were r = 0.61–0.98 for the standard and r = 0.76–0.98 for the stop technique. Bland–Altman analysis showed that the error associated with the standard technique was 37.9% (BP) and 57.5% higher (SQ) than that associated with the stop technique. The biological within-subject variation is significantly reduced when a pause is imposed between the eccentric and concentric phases. Other relevant variables associated to the load–velocity and load–power relationships such as the contribution of the propulsive phase and the load that maximises power output remained basically unchanged.

The purpose of this study was to determine, i) the reliability of blood lactate and ventilatory-based thresholds, ii) the lactate threshold that corresponds with each ventilatory threshold (VT₁ and VT₂) and with maximal lactate steady state test (MLSS) as a proxy of cycling performance. Fourteen aerobically-trained male cyclists ( 62.1±4.6 ml·kg^-1·min^-1) performed two graded exercise tests (50 W warm-up followed by 25 W·min^-1) to exhaustion. Blood lactate, and data were collected at every stage. Workloads at VT₁ (rise in ;) and VT₂ (rise in ) were compared with workloads at lactate thresholds. Several continuous tests were needed to detect the MLSS workload. Agreement and differences among tests were assessed with ANOVA, ICC and Bland-Altman. Reliability of each test was evaluated using ICC, CV and Bland-Altman plots. Workloads at lactate threshold (LT) and LT+2.0 mMol·L^-1 matched the ones for VT₁ and VT₂, respectively (p = 0.147 and 0.539; r = 0.72 and 0.80; Bias = -13.6 and 2.8, respectively). Furthermore, workload at LT+0.5 mMol·L^-1 coincided with MLSS workload (p = 0.449; r = 0.78; Bias = -4.5). Lactate threshold tests had high reliability (CV = 3.4–3.7%; r = 0.85–0.89; Bias = -2.1–3.0) except for D_MAX method (CV = 10.3%; r = 0.57; Bias = 15.4). Ventilatory thresholds show high reliability (CV = 1.6%–3.5%; r = 0.90–0.96; Bias = -1.8–2.9) except for RER = 1 and V-Slope (CV = 5.0–6.4%; r = 0.79; Bias = -5.6–12.4). Lactate threshold tests can be a valid and reliable alternative to ventilatory thresholds to identify the workloads at the transition from aerobic to anaerobic metabolism.

The aim of this study was to determine the effectiveness of physical exercise, respiratory muscle training and the self-management WHO recommendations leaflet on the recovery of physical fitness, quality of life and symptom status in people with post COVID-19 conditions. Eighty non-hospitalized adults with a post-COVID-19 condition were randomly assigned to one of four 8-week parallel intervention groups: multicomponent exercise program based on concurrent training- CT (n= 20; 3 resistance and endurance supervised sessions per week at low-moderate intensity); b) inspiratory muscle training- RM (n= 17; 2 standardized daily sessions); c) a combination of both of the above- CTRM (n= 23); d) control group- CON (n= 20; following the WHO guidelines for post-COVID-19 related illness rehabilitation). No significant differences between groups were detected at baseline. While no significant differences between interventions were detected in the VO_2max, significant individual improvements were identified in the CT (7.5%; ES=0.38) and CTRM (7.8%; ES=0.28) groups. Lower body muscle strength significantly improved in the CT and CTRM (14.5-32.6%; ES=0.27-1.13) groups compared to RM and CON (-0.3-11.3%; ES=0.19-0.00). The CT and CTRM groups improved significantly for dyspnea and fatigue, as did the health status. In addition, significant differences between interventions were described in fatigue and depression scales favouring CT and CTRM interventions. An individualized and supervised concurrent training with or without respiratory muscle training was safer and more effective than self-care recommendations and inspiratory muscle training alone, to regain cardiovascular and muscular fitness, improve symptom severity and health status in outpatients with post-COVID-19 conditions.