Heritability estimates of muscle strength‐related phenotypes: A systematic review and meta‐analysis

The purpose of this study was to clarify the heritability estimates of human muscle strength‐related phenotypes (H²‐msp). A systematic literature search was conducted using PubMed (through August 22, 2016). Studies reporting the H²‐msp for healthy subjects in a sedentary state were included. Random‐effects models were used to calculate the weighted mean heritability estimates. Moreover, subgroup analyses were performed based on phenotypic categories (eg, grip strength, isotonic strength, jumping ability). Sensitivity analyses were also conducted to investigate potential sources of heterogeneity of H²‐msp, which included age and sex. Twenty‐four articles including 58 measurements were included in the meta‐analysis. The weighted mean H²‐msp for all 58 measurements was 0.52 (95% confidence intervals [CI]: 0.48–0.56), with high heterogeneity (I²=91.0%, P<.001). Subgroup analysis showed that the heritability of isometric grip strength, other isometric strength, isotonic strength, isokinetic strength, jumping ability, and other power measurements was 0.56 (95% CI: 0.46–0.67), 0.49 (0.47–0.52), 0.49 (0.32–0.67), 0.49 (0.37–0.61), 0.55 (0.45–0.65), and 0.51 (0.31–0.70), respectively. The H²‐msp decreased with age (P<.05). In conclusion, our results indicate that the influence of genetic and environmental factors on muscle strength‐related phenotypes is comparable. Moreover, the role of environmental factors increased with age. These findings may contribute toward an understanding of muscle strength‐related phenotypes.     

Effects of exercise training on oxygen uptake in coronary heart disease: a systematic review and meta‐analysis

It is not known to what extent exercise programs increase maximal oxygen uptake (VO_2max) in patients with coronary heart diseases (CHD). The purpose of this study is to determine the effect of exercise interventions on VO_2max in subjects with CHD. Database search of randomized controlled trials was conducted from PubMed. Studies were included that reported the characteristics and effects of exercise interventions in subjects with CHD, included a non‐exercise control group and measured VO_2max using direct measurement method. Eighteen studies were eligible. Exercise interventions increased VO_2max by 2.6 ± 1.6 and 0.3 ± 1.4 mL/kg/min in the training and control groups, respectively. The net difference in the change of VO_2max between the groups was 2.3 mL/kg/min with a standardized mean difference of 0.60 [95% CI 0.47, 0.74] (P<0.001). Aerobic training led to a larger difference in VO_2max between the groups than other training modes. Over 6 months of training period and training started within 3 months after a cardiac event also had a significant effect on VO_2max. This analysis showed that a long exercise training period starting soon after a cardiac event improved VO_2max in patients with CHD most effectively. In future studies, the training programs should be designed carefully as even larger improvements in VO_2max may be possible.     

Effects of group sports on health‐related physical fitness of overweight youth: A systematic review and meta‐analysis

Group sports interventions have been developed to improve health‐related physical fitness of overweight/obese youth. However, its benefits are not systematically documented. This study synthesizes the evidence about the effects of group sports on health‐related physical fitness of overweight/obese youth. Pubmed, Web of Knowledge, Scopus, Medline, CINAHL, SportDiscus, and Academic Search Complete were searched in February 2016. Studies assessing the effects of group sports on body composition, cardiorespiratory endurance, muscle strength, flexibility, and neuromotor fitness of overweight/obese youth (aged <18 years) were included. Effect sizes (ES) were calculated with Cohen's d and its 95% confidence intervals (CI). Improvements were found in (i) body composition – percentage of fat body mass (pooled ES = 0.67; 95% CI = 0.24–1.10) and waist circumference (ES = 0.69; P = 0.004); (ii) cardiorespiratory endurance – peak oxygen consumption (pooled ES = 0.53; 95% CI = 0.13–0.92) and (iii) muscle strength – hand grip strength (ES = 0.72; P = 0.003). No significant effects were found for body mass index (pooled ES = 0.27; 95% CI = ?0.14 to 0.69), percentage of lean body mass (ES = 0.01; P > 0.05), maximal power output (ES from 0 to 0.06; P > 0.05), sit‐and‐reach test (pooled ES = 0.26; 95% CI = ?0.16 to 0.68) and agility test (ES = 0; P = 0.48). Group sports improve body composition, cardiorespiratory endurance, and hand grip strength of overweight/obese youth. Flexibility and neuromotor fitness do not seem to change following group sports.     

Effect of training cessation on muscular performance: A meta‐analysis

The purpose of this study was to assess the effect of resistance training cessation on strength performance through a meta‐analysis. Seven databases were searched from which 103 of 284 potential studies met inclusion criteria. Training status, sex, age, and the duration of training cessation were used as moderators. Standardized mean difference (SMD) in muscular performance was calculated and weighted by the inverse of variance to calculate an overall effect and its 95% confidence interval (CI). Results indicated a detrimental effect of resistance training cessation on all components of muscular performance: [submaximal strength; SMD (95% CI) = ?0.62 (?0.80 to ?0.45), P < 0.01], [maximal force; SMD (95% CI) = ?0.46 (?0.54 to ?0.37), P < 0.01], [maximal power; SMD (95% CI) = ?0.20 (?0.28 to ?0.13), P < 0.01]. A dose–response relationship between the amplitude of SMD and the duration of training cessation was identified. The effect of resistance training cessation was found to be larger in older people (> 65 years old). The effect was also larger in inactive people for maximal force and maximal power when compared with recreational athletes. Resistance training cessation decreases all components of muscular strength. The magnitude of the effect differs according to training status, age or the duration of training cessation.     

Which exercise prescriptions optimize V̇O2max during cancer treatment?—A systematic review and meta‐analysis

The aims of the present systematic review and meta‐analysis were to investigate the effect of exercise on maximal oxygen uptake () and to investigate whether exercise frequency, intensity, duration, and volume are associated with changes in among adult patients with cancer undergoing treatment. Medline and Embase through OvidSP were searched to identify randomized controlled trials. Two reviewers extracted data and assessed the risk of bias. The overall effect size and differences in effects for different intensities and frequencies were calculated on change scores and post‐intervention data, and the meta‐regression of exercise duration and volumes was analyzed using the Comprehensive Meta‐Analysis software. Fourteen randomized controlled trials were included in the systematic review, comprising 1332 patients with various cancer types receiving (neo‐)adjuvant chemo‐, radio‐, and/or hormone therapy. Exercise induced beneficial changes in compared to usual care (effect size = 0.46, 95% Confidence Interval = 0.23‐0.69). Longer session duration (P = 0.020), and weekly duration (P = 0.010), larger weekly volume (P < 0.001), and shorter intervention duration (P = 0.005) were significantly associated with more beneficial changes in . No differences in effects between subgroups with respect to frequency and intensity were found. In conclusion, exercise has beneficial effects on in patients with cancer undergoing (neo‐)adjuvant treatment. As interventions with larger exercise volumes and longer session durations resulted in larger beneficial changes in , exercise frequency, intensity, and duration should be considered carefully for sufficient exercise volume to induce changes in for this patient group.     

Female athlete's heart: Systolic and diastolic function related to circulatory dimensions

There are relatively few studies on female athletes examining cardiac size and function and how these measures relate to maximal oxygen uptake (VO_2max). When determining sports eligibility, it is important to know what physiological adaptations and characteristics may be expected in female athletes, taking body and cardiac size into account. The purposes of this study were (a) to compare right and left heart dimensions and function in female endurance athletes (ATH) and in non‐athletic female controls of similar age (CON); and (b) to explore how these measures related to VO_2max. Forty‐six ATH and 48 CON underwent a maximal bicycle exercise test and an echocardiographic examination at rest, including standard and color tissue Doppler investigation. All heart dimensions indexed for body size were larger in ATH (all P < 0.01). The diastolic mitral E/A ratio was 27% higher in ATH (P < 0.001) while systolic left and right atrio‐ventricular longitudinal displacement was 7% (P = 0.002) and 15% (P < 0.001) larger in ATH, respectively. Half (50.3%) of the variability in VO_2max could be explained by left ventricular end‐diastolic volume. Our results could be useful in evaluating female endurance athletes with suspected cardiac disease and contribute to understanding differences between female athletes and non‐athletes.     

Acute and sustained effects of a periodized carbohydrate intake using the sleep‐low model in endurance‐trained males

Repeated periodization of carbohydrate (CHO) intake using a diet‐exercise strategy called the sleep‐low model can potentially induce mitochondrial biogenesis and improve endurance performance in endurance‐trained individuals. However, more studies are needed to confirm the performance‐related effects and to investigate the sustained effects on maximal fat oxidation (MFO) rate and proteins involved in intramuscular lipid metabolism. Thirteen endurance‐trained males (age 23‐44 years; O₂‐max, 63.9 ± 4.6 mL·kg^?1·min^?1) were randomized into two groups: sleep‐low (LOW‐CHO) or high CHO availability (HIGH‐CHO) in three weekly training blocks over 4 weeks. The acute metabolic response was investigated during 60 minutes of exercise within the last 3 weeks of the intervention. Pre‐ and post‐intervention, 30‐minute time‐trial performance was investigated after a 90‐minute pre‐load, which as a novel approach included nine intense intervals (and estimation of MFO). Additionally, muscle biopsies (v. lateralis) were obtained to investigate expression of proteins involved in intramuscular lipid metabolism using Western blotting. During acute exercise, average fat oxidation rate was ~36% higher in LOW‐CHO compared to HIGH‐CHO (P = .03). This did not translate into sustained effects on MFO. Time‐trial performance increased equally in both groups (overall time effect: P = .005). We observed no effect on intramuscular proteins involved in lipolysis (ATGL, G0S2, CGI‐58, HSL) or fatty acid transport and β‐oxidation (CD‐36 and HAD, respectively). In conclusion, the sleep‐low model did not induce sustained effects on MFO, endurance performance, or proteins involved in intramuscular lipid metabolism when compared to HIGH‐CHO. Our study therefore questions the transferability of acute effects of the sleep‐low model to superior sustained adaptations.     

Effects of fasted vs fed‐state exercise on performance and post‐exercise metabolism: A systematic review and meta‐analysis

The effects of nutrition on exercise metabolism and performance remain an important topic among sports scientists, clinical, and athletic populations. Recently, fasted exercise has garnered interest as a beneficial stimulus which induces superior metabolic adaptations to fed exercise in key peripheral tissues. Conversely, pre‐exercise feeding augments exercise performance compared with fasting conditions. Given these seemingly divergent effects on performance and metabolism, an appraisal of the literature is warranted. This review determined the effects of fasting vs pre‐exercise feeding on continuous aerobic and anaerobic or intermittent exercise performance, and post‐exercise metabolic adaptations. A search was performed using the MEDLINE and PubMed search engines. The literature search identified 46 studies meeting the relevant inclusion criteria. The Delphi list was used to assess study quality. A meta‐analysis and meta‐regression were performed where appropriate. Findings indicated that pre‐exercise feeding enhanced prolonged (P  = .012), but not shorter duration aerobic exercise performance (P  = .687). Fasted exercise increased post‐exercise circulating FFAs (P  = .023) compared to fed exercise. It is evidenced that pre‐exercise feeding blunted signaling in skeletal muscle and adipose tissue implicated in regulating components of metabolism, including mitochondrial adaptation and substrate utilization. This review's findings support the hypothesis that the fasted and fed conditions can divergently influence exercise metabolism and performance. Pre‐exercise feeding bolsters prolonged aerobic performance, while seminal evidence highlights potential beneficial metabolic adaptations that fasted exercise may induce in peripheral tissues. However, further research is required to fully elucidate the acute and chronic physiological adaptations to fasted vs fed exercise.     

有氧锻炼对久坐不动生活方式的健康人群最大摄氧量的影响:Meta分析

目的:评价有氧锻炼对最大摄氧量的影响和最有效锻炼强度,为有氧运动处方强度的制定提供依据。方法:以MEDLINE为文献主要来源,搜索1976年至2008年间公开发表的有氧锻炼对最大摄氧量影响的相关文献,根据纳入标准和排除标准选择合适的文献,并对其进行质量评估和相关数据提取。结果:(1)对35篇文献中889名受试者进行Meta分析:最大摄氧量加权均数差为3.61ml/kg/min,95%可信区间为2.96～4.25ml/kg/min,与锻炼前平均最大摄氧量数值(27.26ml/kg/min)相比,锻炼后增加了13.2%。(2)根据锻炼强度的不同进行亚组Meta分析,锻炼强度分别为70～80%最大摄氧量(VO2max)、71～80%最大心率(HRmax)和61～70%储备心率(HRR)时,最大摄氧量增加最多。结论:久坐不动生活方式的健康人群通过有氧锻炼可以提高其最大摄氧量水平,且本研究结果中最有效的锻炼强度为制定有氧运动处方强度提供一定的理论依据。     

Validity of physical activity and cardiorespiratory fitness in the Danish cohort “Diet,Cancer and Health‐Next Generations”

Valid assessments of physical activity (PA) and cardiorespiratory fitness (CRF) are essential in epidemiological studies to define dose‐response relationship for formulating thorough recommendations of an appropriate pattern of PA to maintain good health. The aim of this study was to validate the Danish step test, the physical activity questionnaire Active‐Q, and self‐rated fitness against directly measured maximal oxygen uptake (VO₂max). A population‐based subsample (n=125) was included from the “Diet, Cancer and Health‐Next Generations” (DCH‐NG) cohort which is under establishment. Validity coefficients, which express the correlation between measured and “true” exposure, were calculated, and misclassification across categories was evaluated. The validity of the Danish step test was moderate (women: r=.66, and men: r=.56); however, men were systematically underestimated (43% misclassification). When validating the questionnaire‐derived measures of PA, leisure‐time physical activity was not correlated with VO₂max. Positive correlations were found for sports overall, but these were only significant for men: total hours per week of sports (r=.26), MET‐hours per week of sports (r=.28) and vigorous sports (0.28) alone were positively correlated with VO₂max. Finally, the percentage of misclassification was low for self‐rated fitness (women: 9% and men: 13%). Thus, self‐rated fitness was found to be a superior method to the Danish step test, as well as being less cost prohibitive and more practical than the VO₂max method. Finally, even if correlations were low, they support the potential for questionnaire outcomes, particularly sports, vigorous sports, and self‐rated fitness to be used to estimate CRF.     

Physical exercise intervention in depressive disorders: Meta‐analysis and systematic review

Previous meta‐analyses investigating the effect of exercise on depression have included trials where the control condition has been categorized as placebo despite the fact that this particular placebo intervention (e.g., meditation, relaxation) has been recognized as having an antidepressant effect. Because meditation and mindfulness‐based interventions are associated with depression reduction, it is impossible to separate the effect of the physical exercise from the meditation‐related parts. The present study determined the efficacy of exercise in reducing symptoms of depression compared with no treatment, placebo conditions or usual care among clinically defined depressed adults. Of 89 retrieved studies, 15 passed the inclusion criteria of which 13 studies presented sufficient information for calculating effect sizes. The main result showed a significant large overall effect favoring exercise intervention. The effect size was even larger when only trials that had used no treatment or placebo conditions were analyzed. Nevertheless, effect size was reduced to a moderate level when only studies with high methodological quality were included in the analysis. Exercise may be recommended for people with mild and moderate depression who are willing, motivated, and physically healthy enough to engage in such a program.     

Cardiorespiratory fitness and health‐related quality of life in women at risk for gestational diabetes

This study examined the associations of cardiorespiratory fitness (CRF ) and leisure‐time physical activity (LTPA ) with health‐related quality of life (HRQ oL) in women at risk for gestational diabetes mellitus (GDM ). The participants were 39 women planning pregnancy with a history of GDM and/or BMI >29 kg/m². We assessed CRF by measuring maximal oxygen consumption (VO _2max) during incremental cycle ergometer exercise until voluntary fatigue. LTPA was self‐reported, and HRQ oL assessed with the SF ‐36 Health Survey (SF ‐36). The mean (SD ) VO _2max was 27 (6) mL·kg⁻¹·min⁻¹, and the mean LTPA was 2.6 (1.7) h/wk. After controlling for BMI , VO _2max was positively associated with the SF ‐36 General Health scale (β 1.27, 95% CI: 0.09, 2.44, P =.035) and the Physical Component Summary (β 0.48, 95% CI: 0.14, 0.82, P =.007). The General Health scale (P =.023) and the Physical Component Summary (P =.011) differed even between those with very poor and poor CRF . After controlling for BMI , LTPA was positively associated with the SF ‐36 Physical Functioning scale (r _s=.34, P =.039), the General Health scale (β 3.74, 95% CI: 0.64, 6.84, P =.020), and the Physical Component Summary (β 1.13 95% CI: 0.19, 2.06, P =.020). To conclude, CRF and LTPA were positively associated with perceived general health and physical well‐being in women planning pregnancy and at risk for GDM . Even a slightly better CRF would be beneficial for well‐being among women with low levels of CRF .     

Handgrip and knee extension strength as predictors of cancer mortality: A systematic review and meta‐analysis

The specific role of different strength measures on mortality risk needs to be clarified to gain a better understanding of the clinical importance of different muscle groups, as well as to inform intervention protocols in relation to reducing early mortality. The aim of the systematic review and meta‐analysis was to determine the relationship between muscular strength and risk of cancer mortality. Eligible cohort studies were those that examined the association between muscular strength, as assessed using validated tests, and cancer mortality in healthy youth and adults. The hazard ratio (HR ) estimates obtained were pooled using random effects meta‐analysis models. The outcome was cancer mortality assessed using the HR (Cox proportional hazards model). Eleven prospective studies with 1 309 413 participants were included, and 9787 cancer‐specific deaths were reported. Overall, greater handgrip (HR  = 0.97, 95% CI , 0.92‐1.02; P  =  .055; I ² = 18.9%) and knee extension strength (HR  = 0.98, 95% CI , 0.95‐1.00; P  =  .051; I ² = 60.6%) were barely significant associated with reduced risk of cancer mortality. Our study suggests that higher level of muscular strength is not statistically associated with lower risk of cancer mortality.     

Effects of sprint interval training on VO2max and aerobic exercise performance: A systematic review and meta‐analysis

Recently, several studies have examined whether low‐volume sprint interval training (SIT) may improve aerobic and metabolic function. The objective of this study was to systematically review the existing literature regarding the aerobic and metabolic effects of SIT in healthy sedentary or recreationally active adults. A systematic literature search was performed (Bibliotek.dk, SPORTDiscus, Embase, PEDro, SveMed+, and Pubmed). Meta‐analytical procedures were applied evaluating effects on maximal oxygen consumption (VO_2max). Nineteen unique studies [four randomized controlled trials (RCTs), nine matched‐controlled trials and six noncontrolled studies] were identified, evaluating SIT interventions lasting 2–8 weeks. Strong evidence support improvements of aerobic exercise performance and VO_2max following SIT. A meta‐analysis across 13 studies evaluating effects of SIT on VO_2max showed a weighted mean effects size of g = 0.63 95% CI (0.39; 0.87) and VO_2max increases of 4.2–13.4%. Solid evidence support peripheral adaptations known to increase the oxidative potential of the muscle following SIT, whereas evidence regarding central adaptations was limited and equivocal. Some evidence indicated changes in substrate oxidation at rest and during exercise as well as improved glycemic control and insulin sensitivity following SIT. In conclusion, strong evidence support improvement of aerobic exercise performance and VO_2max following SIT, which coincides with peripheral muscular adaptations. Future RCTs on long‐term SIT and underlying mechanisms are warranted.     

Health‐related physical fitness in children and adolescents with Down syndrome and response to training

Physical fitness is related to health at all ages. Information about physical fitness in the Down syndrome (DS) population, however, is scarce, especially when we consider children and adolescents. A review of the current data available on this topic would be both timely and important as it would serve as a starting point to stimulate new research perspectives. The data we reviewed from the literature showed a general trend toward lower values of physical fitness parameters and worse body composition variables in children and adolescents with DS compared with the population without intellectual disability (ID) or even with the population with ID without DS. Notably, children and adolescents with DS have been described as less active or overprotected; however, these factors may not be the cause of their poor physical fitness. Many of the training programs carried out in children and adolescents with DS did not yield the desired responses, and the reasons are still unknown. The purpose of this review is to summarize the current available literature on health‐related physical fitness in children and adolescents with DS, and the effect of training on these variables. From the literature available, it is clear that more data on this population are necessary.     

Vertical jump in female and male volleyball players: a review of observational and experimental studies

The main purpose of this article was to review a series of studies (n=32; 24 observational and eight experimental) examining vertical jump (VJ) performances in female and male volleyball players. The main findings of this review are (a) players of better performing teams have higher VJ values; (b) strength and conditioning programs that emphasize plyometric training can increase VJ performance; and (c) it is important to continue conditioning sessions throughout the season in order to maintain VJ performance. Three research limitations associated with the testing protocols and the strength and conditioning programs used in the studies were outlined: (a) the use of multiple testing protocols; (b) lack of experimental studies; and (c) lack of data on the effect of VJ performance on achieving success in actual games. Four recommendations for volleyball and strength and conditioning coaches were given: (a) Plyometric training should be included in the annual training program; (b) Interruptions in the conditioning program during the season should be avoided; (c) Overtraining during the pre‐season should be avoided; and (d) VJ performance should be tested throughout the entire season.     

Physical fitness and academic performance in youth: A systematic review

Physical fitness (PF) is a construct of health‐ and skill‐related attributes which have been associated with academic performance (AP) in youth. This study aimed to review the scientific evidence on the association among components of PF and AP in children and adolescents. A systematic review of articles using databases PubMed/Medline, ERIC, LILACS, SciELO, and Web of Science was undertaken. Cross‐sectional and longitudinal studies examining the association between at least one component of PF and AP in children and adolescents, published between 1990 and June 2016, were included. Independent extraction of articles was carried out by the two authors using predefined data fields. From a total of 45 studies included, 25 report a positive association between components of PF with AP and 20 describe a single association between cardiorespiratory fitness (CRF) and AP. According to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines: 12 were classified as low, 32 as medium risk, and 1 as high risk of bias. Thirty‐one studies reported a positive association between AP and CRF, six studies with muscular strength, three studies with flexibility, and seven studies reported a positive association between clustered of PF components and AP. The magnitude of the associations is weak to moderate (β = 0.10–0.42 and odds = 1.01–4.14). There is strong evidence for a positive association between CRF and cluster of PF with AP in cross‐sectional studies; and evidence from longitudinal studies for a positive association between cluster of PF and AP; the relationship between muscular strength and flexibility with AP remains uncertain.