Sedentary behaviors, defined as sitting or lying-down activities involving an energy expenditure of 1.0 to 1.5 basal metabolic equivalents,¹ are considered the fourth greatest risk factor of mortality worldwide.² Specifically, screen media use is the most popular leisure-time sedentary behavior among children and adolescents. Screen media use includes screen-based activities such as internet surfing, computer use, mobile phone use, television viewing, and video game playing.³ On average, during their free time, children and adolescents watch television between 1.8 and 2.8 hours, play video games for 40 minutes, and use a computer 34 minutes per day.³ Quiz Ref ID Overall, 28% of children and adolescents are engaged in these screen-based activities more than 4 hours per day, with higher prevalence among boys than girls (30% vs 25%).³ Along with screen media’s advantages of access to a wide variety of resources and fast communication, use of screen media has been associated with adverse physical, psychological, and social health consequences.^4,5

Madruga-Parera, M, Bishop, C, Fort-Vanmeerhaeghe, A, Beltran-Valls, MR, Gonzalo-Skok, O, and Romero-Rodríguez, D. Interlimb asymmetries in youth tennis players: relationships with performance. J Strength Cond Res 34(10): 2815–2823, 2020—Change of direction speed (CODS) has been highlighted as a critical component of tennis. Interlimb asymmetries have been commonly studied in jump tests, but less attention given to the topic during CODS. The aim of this study was to quantify interlimb asymmetries in jumping and CODS (during traditional and isoinertial tests) and establish their relationship with measures of physical performance. Twenty-two elite youth tennis players (16.3 ± 1.4 years) performed single-leg countermovement jump (SLCMJ), single-leg broad jump, and single-leg lateral jump, a double 180° turn CODS test, and shuffle lateral step and crossover step with an isoinertial resistance device. Paired-samples t-tests revealed significant differences between limbs for all tests (p < 0.05). Interlimb asymmetry scores ranged from 1.83 to 15.03%, and a 1-way repeated-measures analysis of variance showed significant differences between interlimb asymmetry scores across multiple tests (p < 0.05). Spearman's rank order r correlations showed significant negative relationships between CODS asymmetry and SLCMJ performance on both limbs (r = −0.50; p = 0.02 and r = −0.53; p = 0.01) and CODS performance on both limbs (r = 0.50; p = 0.02 and r = 0.63; p = 0.002). These results show the test-specific nature of asymmetries in youth tennis athletes, with the SLCMJ presenting the greatest magnitude of asymmetry. Furthermore, interlimb differences during CODS were associated with reduced performance during jumping and CODS tests, suggesting the monitoring of asymmetries within this population may therefore be warranted.

Regular physical activity is effective as prevention and treatment for different chronic conditions related to the ageing processes. In fact, a sedentary lifestyle has been linked to a worsening of cellular ageing biomarkers such as telomere length (TL) and/or specific epigenetic changes (e.g. DNA methylation), with increase of the propensity to aging-related diseases and premature death. Extending our previous findings, we aimed to test the hypothesis that 12 weeks of low frequency, moderate intensity, explosive-type resistance training (EMRT) may attenuate age-associated genomic changes. To this aim, TL, global DNA methylation, TRF2, Ku80, SIRT1, SIRT2 and global protein acetylation, as well as other proteins involved in apoptotic pathway (Bcl-2, Bax and Caspase-3), antioxidant response (TrxR1 and MnSOD) and oxidative damage (myeloperoxidase) were evaluated before and after EMRT in whole blood or peripheral mononuclear cells (PBMCs) of elderly subjects. Our findings confirm the potential of EMRT to induce an adaptive change in the antioxidant protein systems at systemic level and suggest a putative role of resistance training in the reduction of global DNA methylation. Moreover, we observed that EMRT counteracts the telomeres' shortening in a manner that proved to be directly correlated with the amelioration of redox homeostasis and efficacy of training regime, evaluated as improvement of both muscle's power/strength and functional parameters.

We recently demonstrated that low frequency, moderate intensity, explosive-type resistance training (EMRT) is highly beneficial in elderly subjects towards muscle strength and power, with a systemic adaptive response of anti-oxidant and stress-induced markers. In the present study, we aimed to evaluate the impact of EMRT on oxidative stress biomarkers induced in old people (70-75 years) by a single bout of acute, intense exercise. Sixteen subjects randomly assigned to either a control, not exercising group (n=8) or a trained group performing EMRT protocol for 12-weeks (n=8), were submitted to a graded maximal exercise stress test (GXT) at baseline and after the 12-weeks of EMRT protocol, with blood samples collected before, immediately after, 1 and 24h post-GXT test. Blood glutathione (GSH, GSSG, GSH/GSSG), plasma malonaldehyde (MDA), protein carbonyls and creatine kinase (CK) levels, as well as PBMCs cellular damage (Comet assay, apoptosis) and stress-protein response (Hsp70 and Hsp27 expression) were evaluated. The use of multiple biomarkers allowed us to confirm that EMRT per se neither affected redox homeostasis nor induced any cellular and oxidative damage. Following the GXT, the EMRT group displayed a higher GSH/GSSG ratio and a less pronounced increase in MDA, protein carbonyls and CK levels compared to control group. Moreover, we found that Hsp70 and Hsp27 proteins were induced after GXT only in EMRT group, while any significant modification within 24h was detected in untrained group. Apoptosis rates and DNA damage did not show any significant variation in relation to EMRT and/or GXT. In conclusion, the adherence to an EMRT protocol is able to induce a cellular adaptation allowing healthy elderly trained subjects to cope with the oxidative stress induced by an acute exercise more effectively than the aged-matched sedentary subjects.