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Low-to-moderate altitude (2000–2500 m) training camps are an integral part of many athletes’ training programmes.1 Despite potential positive effects on performance, sojourning at altitude represents an important stress on the human body with transiently increased pulmonary and kidney stress, neuroendocrine dysregulation and immune perturbations.2 This highlights the importance of the careful planning and organisation of altitude training camps, which may be even more critical during the current COVID-19 pandemic. Preliminary reports suggest that hypoxaemia and inflammation induced by COVID-19 result in heterogenous lung injury and acute respiratory distress syndrome, eventually leading to acute respiratory failure.3 Some authors have also speculated that COVID-19-induced acute respiratory distress syndrome may share some similarities with high-altitude pulmonary oedema.4 Even though COVID-19 is primarily a respiratory disease, it can also negatively affect the cardiovascular system, exposing affected patients to myocarditis or myocardial damage.5 Moreover, COVID-19 may impair renal function as well as the circulatory and the immune system. As we move towards the gradual resumption of normal life once the COVID-19 emergency subsides, athletes will also seek to resume their regular training.6 With the cancellation or postponement of almost half of the scheduled sporting events in 2020 (eg, the Tokyo Olympics, many of the cycling tours, World Marathon …

During COVID-19 home confinement, athletes are likely exposed to some level of detraining (i.e. the partial or complete loss of training-induced morphological and physiological adaptations), as a consequence of insufficient and/or inappropriate training stimuli. Such changes may result in impaired performance and increased injury risk if, upon restart, an appropriate sport-specific reconditioning cannot be granted. With this editorial, we aim to recommend extreme caution in sports programming after the COVID-19 emergency

Aim We investigated architectural, functional and molecular responses of human skeletal muscle to concentric (CON) or eccentric (ECC) resistance training (RT). Methods Twelve young males performed 10 weeks of concentric (CON) or eccentric (ECC) resistance training (RT) (n = 6 CON, 6 ECC). An additional 14 males were recruited to evaluate acute muscle fascicle behaviour and molecular signalling in biopsies collected from vastus lateralis (VL) after 30 min of single bouts of CON or ECC exercise. VL volume was measured by magnetic resonance imaging. Muscle architecture (fascicle length, Lf; pennation angle, PA) was evaluated by ultrasonography. Muscle remodelling signals to CON or ECC loading [MAPK/AKT-mammalian target of rapamycin (mTOR) signalling] and inflammatory pathway (TNFαMurf-1-MAFbx) were evaluated by immunoblotting. Results Despite the ~1.2-fold greater load of the ECC group, similar increases in muscle volume (+8% CON and +6% ECC) and in maximal voluntary isometric contraction (+9% CON and +11% ECC) were found after RT. However, increases in Lf were greater after ECC than CON (+12 vs. +5%) while increases in PA were greater in CON than ECC (+30 vs. +5%). Distinct architectural adaptations were associated with preferential growth in the distal regions of VL for ECC (+ECC +8% vs. +CON +2) and mid belly for CON (ECC +7 vs. CON +11%). While MAPK activation (p38MAPK, ERK1/2, p90RSK) was specific to ECC, neither mode affected AKT-mTOR or inflammatory signalling 30 min after exercise. Conclusion Muscle growth with CON and ECC RT occurs with different morphological adaptations reflecting distinct fibre fascicle behaviour and molecular responses.

Aim: Muscle thickness (MT) measured by ultrasound has been used to estimate cross-sectional area (measured by CT and MRI) at a single time-point. We tested whether MT could be used as a valid marker of MRI determined muscle anatomical cross-sectional area (ACSA) and volume changes following resistance training (RT).\ud Methods: Nine healthy, young, male volunteers (24±2 y.o., BMI 24.1±2.8 kg/m2) had vastus lateralis (VL) muscle volume (VOL) and ACSA mid (at 50% of femur length, FL) assessed by MRI, and VL MT measured by ultrasound at 50% FL. Measurements were taken at baseline and after 12 weeks of isokinetic RT. Differences between baseline and post-training were assessed by Student’s paired t-test. The relationships between MRI and ultrasound measurements were tested by Pearson’s correlation. \ud Results: After RT, MT increased by 7.5±6.1% (p0.05).\ud Conclusions: These data support evidence that MT is a reliable index of muscle ACSAmid and VOL at a single time-point. MT changes following RT are associated with parallel changes in muscle ACSAmid but not with the changes in VOL, highlighting the impact of RT on regional hypertrophy.