Dose-response effect of pre-exercise carbohydrates under muscle glycogen unavailability:Insights from McArdle disease

Background:This study aimed to determine the effect of different carbohydrate(CHO)doses on exercise capacity in patients with McArdle disease—the paradigm of“exercise intolerance”,characterized by complete muscle glycogen unavailability—and to determine whether higher exogenous glucose levels affect metabolic responses at the McArdle muscle cell(in vitro)level.Methods:Patients with McArdle disease(n=8)and healthy controls(n=9)underwent a 12-min submaximal cycling constant-load bout followed by a maximal ramp test 15 min after ingesting a non-caloric placebo.In a randomized,double-blinded,cross-over design,patients repeated the tests after consuming either 75 g or 150 g of CHO(glucose:fructose=2:1).Cardiorespiratory,biochemical,perceptual,and electromyographic(EMG)variables were assessed.Additionally,glucose uptake and lactate appearance were studied in vitro in wild-type and McArdle mouse myotubes cultured with increasing glucose concentrations(0.35,1.00,4.50,and 10.00 g/L).Results:Compared with controls,patients showed the“classical”second-wind phenomenon(after prior disproportionate tachycardia,myalgia,and excess electromyographic activity during submaximal exercise,all p<0.05)and an impaired endurance exercise capacity(-51%ventilatory threshold and55%peak power output,both p<0.001).Regardless of the CHO dose(p<0.05 for both doses compared with the placebo),CHO intake increased blood glucose and lactate levels,decreased fat oxidation rates,and attenuated the second wind in the patients.However,only the higher dose increased ventilatory threshold(+27%,p=0.010)and peak power output(+18%,p=0.007).In vitro analyses revealed no differences in lactate levels across glucose concentrations in wild-type myotubes,whereas a doseresponse effect was observed in McArdle myotubes.Conclusion:CHO intake exerts beneficial effects on exercise capacity in McArdle disease,a condition associated with total muscle glycogen unavailability.Some of these benefits are dose dependent.

Effects of a school-based karate intervention on academic achievement,psychosocial functioning,and physical fitness:A multi-country cluster randomized controlled trial

Purpose:To examine the effects of a school-based karate intervention on academic achievement,psychosocial functioning,and physical fitness in children aged 7-8 years.Methods:Twenty schools in 5 different European countries(2 second-grade classrooms per school)participated in a cluster randomized controlled trial(Sport at School trial).Participants were assigned to either a control group,which continued with their habitual physical education lessons,or to an intervention group,which replaced these lessons with a 1-year karate intervention(Karate Mind and Movement program).A total of 721 children(344 girls and 377 boys,7.4±0.5 years old,mean±SD)completed the study,of which 333 and 388 were assigned to the control group and intervention group,respectively.Outcomes included academic performance(average grade),psychosocial functioning(Strengths and Difficulties Questionnaire for parents),and different markers of physical fitness(cardiorespiratory fitness,balance,and flexibility).Results:The intervention provided small but significant benefits compared to the control group for academic achievement(d=0.16;p=0.003),conduct problems(d=-0.28;p=0.003),cardiorespiratory fitness(d=0.36;p<0.001),and balance(d=0.24;p=0.015).There was a trend towards significant benefits for flexibility(d=0.24;p=0.056).No significant benefits were observed for other variables,including psychosocial difficulties,emotional symptoms,hyperactivity/inattention,peer problems,or prosocial behaviour(all p>0.05).Conclusion:A 1-year school-based karate intervention was effective in improving academic achievement,conduct problems,and physical fitness in primary school children.The results support the inclusion of karate during physical education lessons.

Exercise and quality of life in cancer

Historically,patients with cancer were told to avoid physical exertion.This dogma has changed over the last 2 decades,with an exponential growth in the number of studies showing not only the safety,but also the benefits of regular physical activity/exercise in the cancer continuum,notably for attenuating treatment-related toxicities and side effects.

Association between physical activity and cardiovascular risk factors:Dose and sex matter

Dear Editor,ETadegn TagedPFailure to meet World Health Organization(WHO)-determined minimum physical activity(PA)levels is an established risk factor for cardiovascular disease(CVD),^(1)but evidence is still scarce on its effects on other CVD risk factors.Furthermore,whether or not there are sex-specific effects on the association between PA and CVD risk is a matter of controversy,with some authors observing a protective effect of PA in men but not in women,^(2)and others finding the opposite trend.^(3)

Neurocognitive outcomes in pediatric brain tumors after treatment with proton versus photon radiation:a systematic review and meta-analysis

Background Advances in cancer treatments,particularly the development of radiation therapy,have led to improvements in survival outcomes in children with brain tumors.However,radiation therapy is associated with significant long-term neurocognitive morbidity.The present systematic review and meta-analysis aimed to compare the neurocognitive outcomes of children and adolescents with brain tumors treated with photon radiation(XRT)or proton therapy(PBRT).Methods A systematic search was conducted(PubMed,Embase,Cochrane,and Web of Science from inception until 02/01/2022)for studies comparing the neurocognitive outcomes of children and adolescents with brain tumors treated with XRT vs.PBRT.The pooled mean differences(expressed as Z scores)were calculated using a random effects method for those endpoints analyzed by a minimum of three studies.Results Totally 10 studies(n=630 patients,average age range:1–20 years)met the inclusion criteria.Patients who had received PBRT achieved significantly higher scores(difference in Z scores ranging from 0.29–0.75,all P<0.05 and significant in sensitivity analyses)after treatment than those who had received XRT for most analyzed neurocognitive outcomes(i.e.,intelligence quotient,verbal comprehension and perceptual reasoning indices,visual motor integration,and verbal memory).No robust significant differences(P>0.05 in main analyses or sensitivity analyses)were found for nonverbal memory,verbal working memory and working memory index,processing speed index,or focused attention.Conclusions Pediatric brain tumor patients who receive PBRT achieve significantly higher scores on most neurocognitive outcomes than those who receive XRT.Larger studies with long-term follow-ups are needed to confirm these results.

Passive Strategies for the Prevention of Muscle Wasting During Recovery from Sports Injuries

Background Recovery from sport injuries commonly involves a muscle disuse situation(i.e.,reduction in physical activity levels sometimes preceded by joint immobilization)with subsequent negative effects on muscle mass and function.Purpose To summarize the current body of knowledge on the effectiveness of different physical strategies that are currently available to mitigate the negative effects of muscle disuse during recovery from sports injury.Methods A narrative review was conducted to summarize the information available on neuromuscular electrical stimulation(NMES),blood flow restriction(BFR)and vibration intervention.Results The concomitant application of BFR and low-intensity exercise has shown promising results in the prevention of disuse-induced muscle atrophy.Some benefits might also be obtained with BFR alone(i.e.,with no exercise),but evidence is still inconclusive.NMES,which can be applied both passively and synchronously with exercise,can also attenuate most of the negative changes associated with disuse periods.In turn,the mechanical stimulus elicited by vibration seems effec-tive to reduce the loss of bone mineral density that accompanies muscle disuse and could also provide some benefits at the muscle tissue level.Conclusions Different physical strategies are available to attenuate disuse-induced negative consequences during recovery from injury.These interventions can be applied passively,which makes them feasible during the first stages of the recovery.However,it would be advisable to apply these strategies in conjunction with low-intensity voluntary exercise as soon as this is feasible.