Humanin skeletal muscle protein levels increase after resistance training in men with impaired glucose metabolism

Humanin (HN) is a mitochondrially encoded and secreted peptide linked to glucose metabolism and tissue protecting mechanisms. Whether skeletal muscle HN gene or protein expression is influenced by exercise remains unknown. In this intervention study we show, for the first time, that HN protein levels increase in human skeletal muscle following 12 weeks of resistance training in persons with prediabetes. Male subjects (n = 55) with impaired glucose regulation (IGR) were recruited and randomly assigned to resistance training, Nordic walking or a control group. The exercise interventions were performed three times per week for 12 weeks with progressively increased intensity during the intervention period. Biopsies from the vastus lateralis muscle and venous blood samples were taken before and after the intervention. Skeletal muscle and serum protein levels of HN were analyzed as well as skeletal muscle gene expression of the mitochondrially encoded gene MT‐RNR2, containing the open reading frame for HN. To elucidate mitochondrial training adaptation, mtDNA, and nuclear DNA as well as Citrate synthase were measured. Skeletal muscle HN protein levels increased by 35% after 12 weeks of resistance training. No change in humanin protein levels was seen in serum in any of the intervention groups. There was a significant correlation between humanin levels in serum and the improvements in the 2 h glucose loading test in the resistance training group. The increase in HN protein levels in skeletal muscle after regular resistance training in prediabetic males may suggest a role for HN in the regulation of glucose metabolism. Given the preventative effect of exercise on diabetes type 2, the role of HN as a mitochondrially derived peptide and an exercise‐responsive mitokine warrants further investigation.

Moderating Effects of Exercise Duration and Intensity in Neuromuscular vs. Endurance Exercise Interventions for the Treatment of Depression: A Meta-Analytical Review

Background: Exercise training is a beneficial treatment strategy for depression. Previous meta-analytical reviews mainly examined the effect of aerobic exercise on depressive symptoms neglecting comparisons with neuromuscular training and meta-regression considering relevant exercise training prescriptors such as exercise duration, intensity, number of exercise sessions (volume) and frequency. Methods: A structured literature search was conducted in biomedical and psychological databases and study selection was conducted following the PICOS approach. (Randomized) controlled trials that compared supervised neuromuscular or endurance exercise interventions with an inactive control group (CON) in clinically depressed in- or out-patients over 18 years were included. Eligibility and study quality were evaluated by two independent researchers. Standardized mean differences (SMD) for the reduction of depressive symptoms, measured with different evaluation scales (e.g., BDI, HAM-D, PHQ-9, HRSD, MADRS, GDS) were calculated with the adjusted Hedges'g equation as main outcome for the comparison of endurance and neuromuscular exercise interventions vs. CON. Statistical analyses were conducted using a random effects inverse-variance model. Multivariate meta-regression analysis was performed in order to examine the modulating effects of exercise training prescriptors. Results: Twenty seven trials with 1,452 clinically depressed adults were included. 20 out of 27 included trials reached a PEDro score of at least 6, representing high-quality. Irrespective of the exercise mode and study quality, large effects in favor of exercise compared to the control condition were found. Compared to CON, sensitivity analyses revealed a moderate to large effect in favor of endurance exercise [SMD: -0.79 (90% CI: -1.10, -0.48); p < 0.00001, I² = 84%] and a large effect size in favor of neuromuscular exercise [SMD: -1.14 (90 CI: -1.50, -0.78); p < 0.00001, I² = 80%]. These effects decreased to moderate for endurance and remained large for neuromuscular trials when considering studies of high quality, indicating a significant difference (p = 0.04). Multivariate meta- regression revealed that exercise duration in endurance trials and exercise intensity in neuromuscular trials had a significantly moderating effect. Conclusions: Strong neuromuscular exercise interventions can be slightly more effective than endurance exercise interventions. Interestingly, exercise duration and exercise intensity moderated the effect size meaningfully. This result might be used on exercise in depression to increase efficacy.

Comparison of the Effects of Endurance Training on Alternate Days and on Consecutive 4 Days Each Week for 8 Weeks on the Abundance of PGC-1α, CaMKII, NRF-1, mtTFA, and COXIV Proteins in Rat Skeletal Muscle

Qiu, J, Huang, L, Davie, AJ, and Zhou, S. Comparison of the effects of endurance training on alternate days and on consecutive 4 days each week for 8 weeks on the abundance of PGC-1α, CaMKII, NRF-1, mtTFA, and COXIV proteins in rat skeletal muscle. J Strength Cond Res 33(11): 3136-3144, 2019-The aim of this study was to compare the effects of 2 training protocols, training on alternate days (A) or on consecutive 4 days followed by 3 days of rest in each week (C) for 8 weeks, on selected proteins involved in the biogenesis and function of mitochondria in skeletal muscle. Eighty male Sprague Dawley rats were randomly allocated into 10 groups (n = 8 each), including Pre and Post control groups and A or C training groups with 8, 16, 24, and 32 training sessions, respectively. The vastus lateralis and soleus muscle samples were obtained 24 hours after the last training session, or at rest for the controls. The abundance of the proteins for PGC-1α, CaMKII, NRF-1, mtTFA, and COXIV was analyzed by Western blotting. Analysis of the results with 2-way ANOVA showed no significant effect and interaction (training protocol by duration) in abundance of the proteins by the 2 protocols. However, fold changes normalized to control showed significant increases COXIV of the soleus muscle at most time points in both A and C training as indicated by Kruskal-Wallis H tests. There were significant correlations found between the abundance of the measured proteins of the vastus lateralis. The findings suggest that the 2 training protocols with the same intensity and total volume of work would not make a significant difference in respect of the changes in the targeted proteins. Alternative regulatory factors and the responses in different types of muscles to the training programs need to be examined in future research.

Effect of Number of Sprints in an SIT Session on Change in V˙O2max: A Meta-analysis

PURPOSE

Recent meta-analyses indicate that sprint interval training (SIT) improves cardiorespiratory fitness (V˙O2max), but the effects of various training parameters on the magnitude of the improvement remain unknown. The present meta-analysis examined the modifying effect of the number of sprint repetitions in an SIT session on improvements in V˙O2max.

METHODS

The databases PubMed and Web of Science were searched for original studies that have examined pre- and posttraining V˙O2max in adults after ≥2 wk of training consisting of repeated (≥2) Wingate-type cycle sprints, published up to May 1, 2016. Articles were excluded if they were not in English; if they involved patients, athletes, or participants with a mean baseline V˙O2max of >55 mL·kg·min or a mean age <18 yr; and if an SIT trial was combined with another intervention or used intervals shorter than 10 s. A total of 38 SIT trials from 34 studies were included in the meta-analysis. Probabilistic magnitude-based inferences were made to interpret the outcome of the analysis.

RESULTS

The meta-analysis revealed a likely large effect of a typical SIT intervention on V˙O2max (mean ± 90% confidence limits = 7.8% ± 4.0%) with a possibly small modifying effect of the maximum number of sprint repetitions in a training session (-1.2% ± 0.8% decrease per two additional sprint repetitions). Apart from possibly small effects of baseline V˙O2max and age, all other modifying effects were unclear or trivial.

CONCLUSION

We conclude that the improvement in V˙O2max with SIT is not attenuated with fewer sprint repetitions, and possibly even enhanced. This means that SIT protocols can be made more time efficient, which may help SIT to be developed into a viable strategy to impact public health.

The Combined Effects of Exercise, Diet, and a Multi-Ingredient Dietary Supplement on Body Composition and Adipokine Changes in Overweight Adults

BACKGROUND

Very few weight and fat loss supplements undergo finished-product research to examine efficacy. The purpose of this study was to determine the effects of an 8-week diet and exercise program on body composition, hip and waist girth, and adipokines and evaluate whether a dietary supplement containing raspberry ketone, capsaicin, caffeine, garlic, and Citrus aurantium enhanced outcomes.

METHODS

Overweight men and women completed this randomized, placebo-controlled, double-blind study. Participants consumed 4 capsules/d of supplement (EXP; n = 18) or placebo (PLA; n = 18). Participants underwent 8 weeks of daily supplementation, calorie restriction (500 kcal < RMR [resting metabolic rate] × 1.2), and supervised progressive exercise training 3 times a week. Body composition, girth, and adipokines were assessed at baseline and postintervention (T1 and T2).

RESULTS

Significant decreases in weight (-2.6 ± 0.57 kg, p < 0.001), fat mass (-1.8 ± 0.20 kg; p < 0.001), and percentage body fat (-3.7% ± 0.29%, p < 0.001) and a significant increase in lean body mass (LBM; 1.5 ± 0.26 kg; p < 0.001) were seen from T1 to T2 in both groups. For men, only those in the EXP group increased LBM from T1 to T2 (1.3 ± 0.38 kg; p < 0.05). Hip girth was also reduced, with the women in the EXP group (-10.7 ± 2.15 cm, p < 0.001) having a greater reduction. There was a time by group interaction, with significant decreases in leptin (p < 0.001) and significant increases in adiponectin (p < 0.05) in the EXP group.

CONCLUSIONS

Significant improvements in adipokines and leptin support the utility of exercise, diet, and fat loss for impacting inflammatory biomarkers. The improvement in adiponectin with EXP may suggest a unique health mechanism.

Low-intensity aerobic exercise training: inhibition of skeletal muscle atrophy in high-fat-diet-induced ovariectomized rats

PURPOSE

Postmenopausal women are highly susceptible to diseases, such as obesity, type 2 diabetes, osteoporosis, or skeletal muscle atrophy and many people recognize the need for regular physical activity. Aerobic exercise training is known to improve the oxidative capacity and insulin sensitivity of skeletal muscles. This study aimed to investigate the role of low-intensity aerobic exercise training on skeletal muscle protein degradation or synthesis in the plantaris muscles of high-fat-fed ovariectomized rats.

METHODS

Ovariectomized female rats were divided into two groups: a high-fat diet-sedentary group (HFD), and a high-fat diet-aerobic exercise group (HFD+EX). The exercise group exercised aerobically on a treadmill 5 days/week for 8 weeks. The rats progressively ran 30 min/day at 15 m/min, up to 40 min/day at 18 m/min, 0% slope, in the last 4 weeks.

RESULTS

Although aerobic exercise led to significantly increased AMP-activated protein kinase (AMPK) phosphorylation at Thr172, phosphorylation of the mammalian target of rapamycin (mTOR) substrate Thr389 S6K1 level did not decrease. Additionally, even though Akt activity did not increase at Ser473, the atrogin-1 level significantly decreased in the exercise group compared to the non-exercise group. Immunohistochemical staining revealed that high-fat-induced TSC2 protein expression was eliminated in response to aerobic exercise.

CONCLUSION

These results suggest that aerobic exercise can inhibit skeletal muscle protein degradation, but it cannot increase protein synthesis in the plantaris muscle of high-fat-fed ovariectomized rats. Our findings have implications in understanding skeletal muscle mass maintenance with low intensity aerobic exercise in post-menopausal women.

Taurine: A Potential Ergogenic Aid for Preventing Muscle Damage and Protein Catabolism and Decreasing Oxidative Stress Produced by Endurance Exercise

The aim of this study was to evaluate the effects of taurine and chocolate milk supplementation on oxidative stress and protein metabolism markers, and aerobic parameters in triathletes.

Methods: A double-blind, crossover study was conducted with 10 male triathletes, aged 30.9 ± 1.3 year, height 1.79 ± 0.01 m and body weight 77.45 ± 2.4 kg. Three grams of taurine and 400 ml of chocolate milk (TAUchoc), or a placebo (chocolate milk) (CHOC) was ingested post exercise for 8 weeks. Oxidative stress marker levels, and 24 h urinary nitrogen, creatinine, and urea excretion were measured before and after 8 weeks of training and supplementation with TAUchoc or CHOC. A maximal incremental running test on a treadmill was performed in order to evaluate aerobic parameters: V_max, heart rate (HR) and rate of perceived exertion (RPE).

Results: TAUchoc treatment during the 8 weeks resulted in increased taurine plasma levels (PRE 201.32 ± 29.03 μmol/L and POST 234.36 ± 35.51 μmol/L, p = 0.01), decreased malondialdehyde levels (19.4%, p = 0.03) and urinary nitrogen excretion (−33%, p = 0.03), and promoted positive nitrogen balance (p = 0.01). There were no changes in reduced glutathione (TAUchoc PRE 0.72 ± 0.08 mmol/L and POST 0.83 ± 0.08 mmol/L; CHOC PRE 0.69 ± 0.08 mmol/L and POST 0.81 ± 0.06 mmol/L), vitamin E plasma levels (TAUchoc PRE 33.99 ± 2.52 μmol/L and 35.95 ± 2.80 μmol/L and CHOC PRE 31.48 ± 2.12 μmol/L and POST 33.77 ± 3.64 μmol/L), or aerobic parameters, which were obtained in the last phase of the maximal incremental running test (V_max TAUchoc PRE 13 ± 1.4 km/h and POST 13.22 ± 1.34 km/h; CHOC PRE 13.11 ± 2.34 km/h and POST 13.11 ± 2.72 km/h), the heart rate values were TAUchoc PRE 181.89 ± 24.18 bpm and POST 168.89 ± 46.56 bpm; CHOC PRE 181.56 ± 2.14 bpm and POST 179.78 ± 3.4 bpm, and the RPE were TAUchoc PRE 8.33 ± 2.4 AU and POST 9.1 ± 2.1 AU; CHOC PRE 8.11 ± 4.94 AU and POST 8.78 ± 2.78 AU).

Conclusion: Taurine supplementation did not improve aerobic parameters, but was effective in increasing taurine plasma levels and decreasing oxidative stress markers, which suggests that taurine may prevent oxidative stress in triathletes.

Chronic effects of superimposed electromyostimulation during cycling on aerobic and anaerobic capacity

PURPOSE

To examine if chronic endurance training by means of simultaneously applied, superimposed electromyostimulation (EMS) can be used to improve performance and physiological core parameters compared to the traditional cycling.

METHODS

Twenty-one male subjects (VO_2peak 55.2 ± 5.1 ml min^- 1 kg^- 1) were assigned to either a cycling (C) or cycling with superimposed EMS (C + E) group. Before and after the 4-week training period, including 14 sessions of moderate cycling [60 min at 60% peak power output (PPO)], participants performed a 20-min time-trial, a step test to exhaustion, a 30-s isokinetic sprint test, and maximum force- and power-tests. Markers of muscle damage and metabolic condition were assessed during the training period.

RESULTS

Step test results revealed increases in PPO, VO_2peak, lactate threshold 1, and the anaerobic threshold for both groups (p < 0.05). Mean power output (MPO) obtained from time-trial was improved in C and C + E (p < 0.05). Isokinetic sprint test revealed increased PPO in both groups, whereas MPO was only changed in C (p < 0.05). Strength parameters were unaffected. Although metabolic stimuli and markers of muscle damage were higher in C + E compared to C, improvements of endurance performance and capacity were not significantly different between C and C + E.

CONCLUSIONS

Despite a higher metabolic, respiratory, and muscular demand, chronic additional superimposed EMS during cycling does not result in superior improvements in endurance and strength performance compared to the traditional cycling.

Resistance training to improve type 2 diabetes: working toward a prescription for the future

The prevalence of type 2 diabetes (T2D) is rapidly increasing, and effective strategies to manage and prevent this disease are urgently needed. Resistance training (RT) promotes health benefits through increased skeletal muscle mass and qualitative adaptations, such as enhanced glucose transport and mitochondrial oxidative capacity. In particular, mitochondrial adaptations triggered by RT provide evidence for this type of exercise as a feasible lifestyle recommendation to combat T2D, a disease typically characterized by altered muscle mitochondrial function. Recently, the synergistic and antagonistic effects of combined training and Metformin use have come into question and warrant more in-depth prospective investigations. In the future, clinical intervention studies should elucidate the mechanisms driving RT-mitigated mitochondrial adaptations in muscle and their link to improvements in glycemic control, cholesterol metabolism and other cardiovascular disease risk factors in individuals with T2D.

Effects of light-load maximal lifting velocity weight training vs. combined weight training and plyometrics on sprint, vertical jump and strength performance in adult soccer players

OBJECTIVES

The purpose of this study was to compare the effects of combined light-load maximal lifting velocity weight training (WT) and plyometric training (PT) with WT alone on strength, jump and sprint performance in semiprofessional soccer players.

DESIGN

Experimental, pre-post tests measures.

METHODS

Thirty adult soccer players were randomly assigned into three groups: WT alone (FSG, n=10), WT combined to jump and sprint exercises (COM, n=10) and control group (CG, n=10). WT consisted of full squat with low load (∼45-60% 1RM) and low volume (4-6 repetitions). Training program was performed twice a week for 6 weeks of competitive season in addition to 4 soccer sessions a week. Sprint time in 10 and 20m, jump height (CMJ), estimated one-repetition maximum (1RM_est) and velocity developed against different absolute loads in full squat were measured before and after training period.

RESULTS

Both experimental groups showed significant improvements in 1RM_est (17.4-13.4%; p<0.001), CMJ (7.1-5.2%; p<0.001), sprint time (3.6-0.7%; p<0.05-0.001) and force-velocity relationships (16.9-6.1%; p<0.05-0.001), whereas no significant gains were found in CG. No significant differences were found between FSG and COM.

CONCLUSIONS

Despite FSG resulted of greater increases in strength variables than COM, this may not translate into superior improvements in the sport-related performance. In fact, COM showed higher efficacy of transfer of strength gains to sprint ability. Therefore, these findings suggest that a combined WT and PT program could represent a more efficient method for improving activities which involve acceleration, deceleration and jumps compared to WT alone.

Evaluation of Performance Improvements After Either Resistance Training or Sprint Interval-Based Concurrent Training

Laird IV, RH, Elmer, DJ, Barberio, MD, Salom, LP, Lee, KA, and Pascoe, DD. Evaluation of performance improvements after either resistance training or sprint interval-based concurrent training. J Strength Cond Res 30(11): 3057-3065, 2016-The purpose of this investigation was to examine the effects of concurrent sprint interval and resistance training (CST) vs. resistance training (RT) on measures of strength, power, and aerobic fitness in recreationally active women. Twenty-eight women (20.3 ± 1.7 years; 63.0 ± 9.1; 51.1 ± 7.1 1 repetition maximum (1-RM) back squat (kg); V[Combining Dot Above]O2max: 35.4 ± 4.1 ml·kg·min) were recruited to complete an 11-week training program. Participants were matched-pair assigned to CST or RT cohorts after preliminary testing, which consisted of 1-RM back squats, maximal isometric squats, anaerobic power evaluations, and maximal oxygen consumption. All subjects trained 3 days per week with sprint-interval training occurring at least 4 hours after RT in the CST cohort. Both CST and RT resulted in significant improvements (p ≤ 0.05) in the 1-RM back squat (37.5 ± 7.8; 40.0 ± 9.6 kg), maximal isometric force (55.7 ± 51.3; 53.7 ± 36.7 kg), average peak anaerobic power testing (7.4 ± 6.2; 7.6 ± 6.4%), and zero-incline treadmill velocity, resulting in maximal oxygen consumption (1.8 ± 0.6; 0.8 ± 0.6 km·h). Only zero-incline treadmill velocity demonstrated a group-by-time interaction with a greater improvement after CST (p < 0.01). Rate of force development was not altered in either group. Results provide no evidence of interference to the adaptive process by CST. Coaches desiring improvements in strength, power, and endurance may want to evaluate how spring and high-intensity interval training might supplement programs already in place.

Mitochondrial adaptations in aged skeletal muscle: effect of exercise training

The aging process is associated with a decline in mitochondrial functions. Mitochondria dysfunction is involved in initiation and progression of many health problems including neuromuscular, metabolic and cardiovascular diseases. It is well known that endurance exercise improves mitochondrial function, especially in the elderly. However, recent studies have demonstrated that resistance training lead also to substantial increases in mitochondrial function in skeletal muscle. A comprehensive understanding of the cellular mechanisms involved in the skeletal muscle mitochondrial adaptations to exercise training in healthy elderly subjects, can help practitioners to design and prescribe more effective exercise trainings.

Circulating MicroRNAs as Potential Biomarkers of Exercise Response

Systematic physical activity increases physical fitness and exercise capacity that lead to the improvement of health status and athletic performance. Considerable effort is devoted to identifying new biomarkers capable of evaluating exercise performance capacity and progress in training, early detection of overtraining, and monitoring health-related adaptation changes. Recent advances in OMICS technologies have opened new opportunities in the detection of genetic, epigenetic and transcriptomic biomarkers. Very promising are mainly small non-coding microRNAs (miRNAs). miRNAs post-transcriptionally regulate gene expression by binding to mRNA and causing its degradation or inhibiting translation. A growing body of evidence suggests that miRNAs affect many processes and play a crucial role not only in cell differentiation, proliferation and apoptosis, but also affect extracellular matrix composition and maintaining processes of homeostasis. A number of studies have shown changes in distribution profiles of circulating miRNAs (c-miRNAs) associated with various diseases and disorders as well as in samples taken under physiological conditions such as pregnancy or physical exercise. This overview aims to summarize the current knowledge related to the response of blood c-miRNAs profiles to different modes of exercise and to highlight their potential application as a novel class of biomarkers of physical performance capacity and training adaptation.

High muscular fitness has a powerful protective cardiometabolic effect in adults: influence of weight status

BACKGROUND

Low levels of muscular fitness (MF) are recognized as an important marker of nutritional status and a predictor of metabolic complications, cardiovascular disease and death, however, the relationship between MF, body mass index (BMI) and the subsequent cardiometabolic protective effects has been less studied among Latin American populations. This study identified an association between MF and the cardiometabolic risk score index (CMRSI) and the lipid-metabolic cardiovascular risk index (LMCRI) in a wide sample of university students grouped according to their BMI.

METHODS

Six thousand ninety five healthy males (29.6 ± 11.7 year-old) participated in the study. Absolute strength was measured using a T.K.K. analogue dynamometer (handgrip), and the participant's strength was then calculated relative to their body mass (MF/BM). The LMCRI was derived from the levels of triglycerides, low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), and glucose levels in a blood sample. The CMRSI was calculated by summing the standardized residuals (z-score) for waist circumference, total cholesterol, LDL-c, triglycerides, HDL-c, and median blood pressure. Subjects were divided into six subgroups according to BMI (normal vs. overweight/obese) and MF/BM tertiles (unfit, average, fit).

RESULTS

The group of participants with low and moderate levels of MF/BM showed higher CMRSI values independent of BMI (P < 0.001). The group with normal BMI and high MF/BM had the highest levels of cardiometabolic protection. All overweight/obese BMI groups had significantly higher LMCRI values independent of the level of MF/BM (P < 0.001).

CONCLUSIONS

Participants with high MF/BM showed reduced cardiometabolic risk, which increased significantly when they were within normal parameters.

Physical Fitness Among Swedish Military Conscripts and Long-Term Risk for Type 2 Diabetes Mellitus: A Cohort Study

BACKGROUND

Early-life physical fitness has rarely been examined in relation to type 2 diabetes mellitus (DM) in adulthood because of the lengthy follow-up required. Elucidation of modifiable risk factors at young ages may help facilitate earlier and more effective interventions.

OBJECTIVE

To examine aerobic capacity and muscle strength at age 18 years in relation to risk for type 2 DM in adulthood.

DESIGN

National cohort study.

SETTING

Sweden.

PARTICIPANTS

1 534 425 military conscripts from 1969 to 1997 (97% to 98% of all men aged 18 years nationwide) without prior type 2 DM.

MEASUREMENTS

Aerobic capacity and muscle strength (measured in watts and newtons per kilogram of body weight, respectively) were examined in relation to type 2 DM identified from outpatient and inpatient diagnoses from 1987 to 2012 (maximum age, 62 years).

RESULTS

34 008 men were diagnosed with type 2 DM in 39.4 million person-years of follow-up. Low aerobic capacity and muscle strength were independently associated with increased risk for type 2 DM. The absolute difference in cumulative incidence of type 2 DM between the lowest and highest tertiles of both aerobic capacity and strength was 0.22% at 20 years of follow-up (95% CI, 0.20% to 0.25%), 0.76% at 30 years (CI, 0.71% to 0.81%), and 3.97% at 40 years (CI, 3.87% to 4.06%). Overall, the combination of low aerobic capacity and muscle strength was associated with a 3-fold risk for type 2 DM (adjusted hazard ratio, 3.07 [CI, 2.88 to 3.27]; P < 0.001), with a positive additive interaction (P < 0.001). These associations were seen even among men with normal body mass index.

LIMITATION

This cohort did not include women and did not measure physical fitness at older ages.

CONCLUSION

In this large cohort of Swedish male military conscripts, low aerobic capacity and muscle strength at age 18 years were associated with increased long-term risk for type 2 DM, even among those with normal body mass index.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Aerobic exercise augments muscle transcriptome profile of resistance exercise

Recent reports suggest that aerobic exercise may boost the hypertrophic response to short-term resistance training. This study explored the effects of an acute aerobic exercise bout on the transcriptional response to subsequent resistance exercise. Ten moderately trained men performed ∼45 min cycling on one leg followed by 4 × 7 maximal knee extensions for each leg, 15 min later. Thus, one limb performed aerobic and resistance exercise (AE + RE) while the opposing leg did resistance exercise only (RE). Biopsies were obtained from the vastus lateralis muscle of each leg 3 h after the resistance exercise bout. Using DNA microarray, we analyzed differences [≥1.5-fold, false discovery rate (FDR) ≤10%] in gene expression profiles for the two modes of exercise. There were 176 genes up (127)- or downregulated (49) by AE + RE compared with RE. Among the most significant differentially expressed genes were established markers for muscle growth and oxidative capacity, novel cytokines, transcription factors, and micro-RNAs (miRNAs). The most enriched functional categories were those linked to carbohydrate metabolism and transcriptional regulation. Upstream analysis revealed that vascular endothelial growth factor, cAMP-response element-binding protein, Tet methylcytosine dioxygenase, and mammalian target of rapamycin were regulators highly activated by AE + RE, whereas JnK, NF-κβ, MAPK, and several miRNAs were inhibited. Thus, aerobic exercise alters the skeletal muscle transcriptional signature of resistance exercise to initiate important gene programs promoting both myofiber growth and improved oxidative capacity. These results provide novel insight into human muscle adaptations to diverse exercise modes and offer the very first genomic basis explaining how aerobic exercise may augment, rather than compromise, muscle growth induced by resistance exercise.

Aquatic exercise for the treatment of knee and hip osteoarthritis

BACKGROUND

Osteoarthritis is a chronic disease characterized by joint pain, tenderness, and limitation of movement. At present, no cure is available. Thus only treatment of the person's symptoms and treatment to prevent further development of the disease are possible. Clinical trials indicate that aquatic exercise may have advantages for people with osteoarthritis. This is an update of a published Cochrane review.

OBJECTIVES

To evaluate the effects of aquatic exercise for people with knee or hip osteoarthritis, or both, compared to no intervention.

SEARCH METHODS

We searched the following databases up to 28 April 2015: the Cochrane Central Register of Controlled Trials (CENTRAL; the Cochrane Library Issue 1, 2014), MEDLINE (from 1949), EMBASE (from 1980), CINAHL (from 1982), PEDro (Physiotherapy Evidence Database), and Web of Science (from 1945). There was no language restriction.

SELECTION CRITERIA

Randomized controlled clinical trials of aquatic exercise compared to a control group (e.g. usual care, education, social attention, telephone call, waiting list for surgery) of participants with knee or hip osteoarthritis.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, extracted data and assessed risk of bias of the included trials. We analysed the pooled results using standardized mean difference (SMD) values.

MAIN RESULTS

Nine new trials met the inclusion criteria and we excluded two earlier included trials. Thus the number of participants increased from 800 to 1190 and the number of included trials increased from six to 13. Most participants were female (75%), with an average age of 68 years and a body mass index (BMI) of 29.4. Osteoarthritis duration was 6.7 years, with a great variation of the included participants. The mean aquatic exercise duration was 12 weeks. We found 12 trials at low to unclear risk of bias for all domains except blinding of participants and personnel. They showed that aquatic exercise caused a small short term improvement compared to control in pain (SMD -0.31, 95% CI -0.47 to -0.15; 12 trials, 1076 participants) and disability (SMD -0.32, 95% CI -0.47 to -0.17; 12 trials, 1059 participants). Ten trials showed a small effect on quality of life (QoL) (SMD -0.25, 95% CI -0.49 to -0.01; 10 trials, 971 participants). These effects on pain and disability correspond to a five point lower (95% CI three to eight points lower) score on mean pain and mean disability compared to the control group (scale 0 to 100), and a seven point higher (95% CI 0 to 13 points higher) score on mean QoL compared with control group (scale 0 to 100). No included trials performed a radiographic evaluation. No serious adverse events were reported in the included trials with relation to aquatic exercise.

AUTHORS' CONCLUSIONS

There is moderate quality evidence that aquatic exercise may have small, short-term, and clinically relevant effects on patient-reported pain, disability, and QoL in people with knee and hip OA. The conclusions of this review update does not change those of the previous published version of this Cochrane review.

A comparison of PGC-1α mRNA and protein expression in response to 1-week endurance training on alternate days or 4 consecutive days

To understand the molecular mechanisms of adaptation to different training protocols, this study compared the effects of 4 sessions of 90 min treadmill exercise on alternate days or consecutive days in 1 week on messenger RNA (mRNA) and protein expression of proliferator-activated receptor-γ coactivator 1-α in rat gastrocnemius muscle. The mRNA significantly increased by 25.8-fold after alternate-day and 10.1-fold after consecutive-day training, while the protein showed no significant cumulative effect, 1.5-1.7-fold above baseline, in the 2 protocols.

Short-term low-intensity blood flow restricted interval training improves both aerobic fitness and muscle strength

The present study aimed to analyze and compare the effects of four different interval-training protocols on aerobic fitness and muscle strength. Thirty-seven subjects (23.8 ± 4 years; 171.7 ± 9.5 cm; 70 ± 11 kg) were assigned to one of four groups: low-intensity interval training with (BFR, n = 10) or without (LOW, n = 7) blood flow restriction, high-intensity interval training (HIT, n = 10), and combined HIT and BFR (BFR + HIT, n = 10, every session performed 50% as BFR and 50% as HIT). Before and after 4 weeks training (3 days a week), the maximal oxygen uptake (VO2max ), maximal power output (Pmax ), onset blood lactate accumulation (OBLA), and muscle strength were measured for all subjects. All training groups were able to improve OBLA (BFR, 16%; HIT, 25%; HIT + BFR, 22%; LOW, 6%), with no difference between groups. However, VO2max and Pmax improved only for BFR (6%, 12%), HIT (9%, 15%) and HIT + BFR (6%, 11%), with no difference between groups. Muscle strength gains were only observed after BFR training (11%). This study demonstrates the advantage of short-term low-intensity interval BFR training as the single mode of training able to simultaneously improve aerobic fitness and muscular strength.

The effect of inter-set rest intervals on resistance exercise-induced muscle hypertrophy

Due to a scarcity of longitudinal trials directly measuring changes in muscle girth, previous recommendations for inter-set rest intervals in resistance training programs designed to stimulate muscular hypertrophy were primarily based on the post-exercise endocrinological response and other mechanisms theoretically related to muscle growth. New research regarding the effects of inter-set rest interval manipulation on resistance training-induced muscular hypertrophy is reviewed here to evaluate current practices and provide directions for future research. Of the studies measuring long-term muscle hypertrophy in groups employing different rest intervals, none have found superior muscle growth in the shorter compared with the longer rest interval group and one study has found the opposite. Rest intervals less than 1 minute can result in acute increases in serum growth hormone levels and these rest intervals also decrease the serum testosterone to cortisol ratio. Long-term adaptations may abate the post-exercise endocrinological response and the relationship between the transient change in hormonal production and chronic muscular hypertrophy is highly contentious and appears to be weak. The relationship between the rest interval-mediated effect on immune system response, muscle damage, metabolic stress, or energy production capacity and muscle hypertrophy is still ambiguous and largely theoretical. In conclusion, the literature does not support the hypothesis that training for muscle hypertrophy requires shorter rest intervals than training for strength development or that predetermined rest intervals are preferable to auto-regulated rest periods in this regard.

Strength training in soccer with a specific focus on highly trained players

Background

Data concerning the physical demands of soccer (e.g., activity pattern) suggest that a high level of performance requires well-developed neuromuscular function (NF). Proficient NF may be relevant to maintain and/or increase players’ short- (intense periods of soccer-specific activity; accelerations, decelerations, and sprinting) and long-term performance during a match and throughout the season.

Objective

This review examines the extent to which distinct modes of strength training improve soccer players’ performance, as well as the effects of concurrent strength and endurance training on the physical capacity of players.

Data sources

A selection of studies was performed in two screening phases. The first phase consisted of identifying articles through a systematic search using relevant databases, including the US National Library of Medicine (PubMed), MEDLINE, and SportDiscus. Several permutations of keywords were utilized (e.g., soccer; strength; power; muscle function), along with the additional scanning of the reference lists of relevant manuscripts. Given the wide range of this review, additional researchers were included. The second phase involved applying six selection criteria to the articles.

Results and conclusions

After the two selection phases, 24 manuscripts involving a total sample of 523 soccer players were considered. Our analysis suggests that professional players need to significantly increase their strength to obtain slight improvements in certain running-based actions (sprint and change of direction speed). Strength training induces greater performance improvements in jump actions than in running-based activities, and these achievements varied according to the motor task [e.g., greater improvements in acceleration (10 m) than in maximal speed (40 m) running movements and in non-squat jump (SJ) than in SSC-based actions (countermovement jump)]. With regard to the strength/power training methods used by soccer players, high-intensity resistance training seems to be more efficient than moderate-intensity resistance training (hypertrophic). From a training frequency perspective, two weekly sessions of strength training are sufficient to increase a player’s force production and muscle power-based actions during pre-season, with one weekly session being adequate to avoid in-season detraining. Nevertheless, to further improve performance during the competitive period, training should incorporate a higher volume of soccer-specific power-based actions that target the neuromuscular system. Combined strength/power training programs involving different movement patterns and an increased focus on soccer-specific power-based actions are preferred over traditional resistance exercises, not only due to their superior efficiency but also due to their ecological value. Strength/power training programs should incorporate a significant number of exercises targeting the efficiency of stretch-shortening-cycle activities and soccer-specific strength-based actions. Manipulation of training surfaces could constitute an important training strategy (e.g., when players are returning from an injury). In addition, given the conditional concurrent nature of the sport, concurrent high-intensity strength and high-intensity endurance training modes (HIT) may enhance a player’s overall performance capacity.

Our analysis suggests that neuromuscular training improves both physiological and physical measures associated with the high-level performance of soccer players.

Electronic supplementary material

The online version of this article (doi:10.1186/s40798-015-0006-z) contains supplementary material, which is available to authorized users.

Resistance exercise-induced S6K1 kinase activity is not inhibited in human skeletal muscle despite prior activation of AMPK by high-intensity interval cycling

Combining endurance and strength training in the same session has been reported to reduce the anabolic response to the latter form of exercise. The underlying mechanism, based primarily on results from rodent muscle, is proposed to involve AMPK-dependent inhibition of mTORC1 signaling. This hypothesis was tested in eight trained male subjects who in randomized order performed either resistance exercise only (R) or interval cycling followed by resistance exercise (ER). Biopsies taken from the vastus lateralis before and after endurance exercise and repeatedly after resistance exercise were assessed for glycogen content, kinase activity, protein phosphorylation, and gene expression. Mixed muscle fractional synthetic rate was measured at rest and during 3 h of recovery using the stable isotope technique. In ER, AMPK activity was elevated immediately after both endurance and resistance exercise (∼90%, P < 0.05) but was unchanged in R. Thr(389) phosphorylation of S6K1 was increased severalfold immediately after exercise (P < 0.05) in both trials and increased further throughout recovery. After 90 and 180 min recovery, S6K1 activity was elevated (∼55 and ∼110%, respectively, P < 0.05) and eukaryotic elongation factor 2 phosphorylation was reduced (∼55%, P < 0.05) with no difference between trials. In contrast, markers for protein catabolism were differently influenced by the two modes of exercise; ER induced a significant increase in gene and protein expression of MuRF1 (P < 0.05), which was not observed following R exercise only. In conclusion, cycling-induced elevation in AMPK activity does not inhibit mTOR complex 1 signaling after subsequent resistance exercise but may instead interfere with the hypertrophic response by influencing key components in protein breakdown.

Interference between concurrent resistance and endurance exercise: molecular bases and the role of individual training variables

Concurrent training is defined as simultaneously incorporating both resistance and endurance exercise within a periodized training regime. Despite the potential additive benefits of combining these divergent exercise modes with regards to disease prevention and athletic performance, current evidence suggests that this approach may attenuate gains in muscle mass, strength, and power compared with undertaking resistance training alone. This has been variously described as the interference effect or concurrent training effect. In recent years, understanding of the molecular mechanisms mediating training adaptation in skeletal muscle has emerged and provided potential mechanistic insight into the concurrent training effect. Although it appears that various molecular signaling responses induced in skeletal muscle by endurance exercise can inhibit pathways regulating protein synthesis and stimulate protein breakdown, human studies to date have not observed such molecular 'interference' following acute concurrent exercise that might explain compromised muscle hypertrophy following concurrent training. However, given the multitude of potential concurrent training variables and the limitations of existing evidence, the potential roles of individual training variables in acute and chronic interference are not fully elucidated. The present review explores current evidence for the molecular basis of the specificity of training adaptation and the concurrent interference phenomenon. Additionally, insights provided by molecular and performance-based concurrent training studies regarding the role of individual training variables (i.e., within-session exercise order, between-mode recovery, endurance training volume, intensity, and modality) in the concurrent interference effect are discussed, along with the limitations of our current understanding of this complex paradigm.

The order of exercise during concurrent training for rehabilitation does not alter acute genetic expression, mitochondrial enzyme activity or improvements in muscle function

Concurrent exercise combines different modes of exercise (e.g., aerobic and resistance) into one training protocol, providing stimuli meant to increase muscle strength, aerobic capacity and mass. As disuse is associated with decrements in strength, aerobic capacity and muscle size concurrent training is an attractive modality for rehabilitation. However, interference between the signaling pathways may result in preferential improvements for one of the exercise modes. We recruited 18 young adults (10 ♂, 8 ♀) to determine if order of exercise mode during concurrent training would differentially affect gene expression, protein content and measures of strength and aerobic capacity after 2 weeks of knee-brace induced disuse. Concurrent exercise sessions were performed 3x/week for 6 weeks at gradually increasing intensities either with endurance exercise preceding (END>RES) or following (RES>END) resistance exercise. Biopsies were collected from the vastus lateralis before, 3 h after the first exercise bout and 48 h after the end of training. Concurrent exercise altered the expression of genes involved in mitochondrial biogenesis (PGC-1α, PRC, PPARγ), hypertrophy (PGC-1α4, REDD2, Rheb) and atrophy (MuRF-1, Runx1), increased electron transport chain complex protein content, citrate synthase and mitochondrial cytochrome c oxidase enzyme activity, muscle mass, maximum isometric strength and VO_2peak. However, the order in which exercise was completed (END>RES or RES>END) only affected the protein content of mitochondrial complex II subunit. In conclusion, concurrent exercise training is an effective modality for the rehabilitation of the loss of skeletal muscle mass, maximum strength, and peak aerobic capacity resulting from disuse, regardless of the order in which the modes of exercise are performed.

Performance and neuromuscular adaptations following differing ratios of concurrent strength and endurance training

The interference effect attenuates strength and hypertrophic responses when strength and endurance training are conducted concurrently; however, the influence of training frequency on these responses remain unclear when varying ratios of concurrent strength and endurance training are performed. Therefore, the purpose of the study was to examine the strength, limb girth, and neuromuscular adaptations to varying ratios of concurrent strength and endurance training. Twenty-four men with >2 years resistance training experience completed 6 weeks of 3 days per week of (a) strength training (ST), (b) concurrent strength and endurance training ratio 3:1 (CT3), (c) concurrent strength and endurance training ratio 1:1 (CT1), or (d) no training (CON) in an isolated limb model. Assessments of maximal voluntary contraction by means of isokinetic dynamometry leg extensions (maximum voluntary suppression [MVC]), limb girth, and neuromuscular responses through electromyography (EMG) were conducted at baseline, mid-intervention, and postintervention. After training, ST and CT3 conditions elicited greater MVC increases than CT1 and CON conditions (p ≤ 0.05). Strength training resulted in significantly greater increases in limb girth than both CT1 and CON conditions (p = 0.05 and 0.004, respectively). The CT3 induced significantly greater limb girth adaptations than CON condition (p = 0.04). No effect of time or intervention was observed for EMG (p > 0.05). In conclusion, greater frequencies of endurance training performed increased the magnitude of the interference response on strength and limb girth responses after 6 weeks of 3 days a week of training. Therefore, the frequency of endurance training should remain low if the primary focus of the training intervention is strength and hypertrophy.

Impact of exercise type and dose on pain and disability in knee osteoarthritis: a systematic review and meta-regression analysis of randomized controlled trials

OBJECTIVE

To identify the optimal exercise program, characterized by type and intensity of exercise, length of program, duration of individual supervised sessions, and number of sessions per week, for reducing pain and patient-reported disability in knee osteoarthritis (OA).

METHODS

A systematic review and meta-analysis of randomized controlled trials were performed. Standardized mean differences (SMDs) were combined using a random-effects model. Study-level covariates were applied in meta-regression analyses in order to reduce between-study heterogeneity.

RESULTS

Forty-eight trials were included. Similar effects in reducing pain were found for aerobic, resistance, and performance exercise (SMD 0.67, 0.62, and 0.48, respectively; P = 0.733). These single-type exercise programs were more efficacious than programs that included different exercise types (SMD 0.61 versus 0.16; P < 0.001). The effect of aerobic exercise on pain relief increased with an increased number of supervised sessions (slope 0.022 [95% confidence interval 0.002, 0.043]). More pain reduction occurred with quadriceps-specific exercise than with lower limb exercise (SMD 0.85 versus 0.39; P = 0.005) and when supervised exercise was performed at least 3 times a week (SMD 0.68 versus 0.41; P = 0.017). No impact of intensity, duration of individual sessions, or patient characteristics was found. Similar results were found for the effect on patient-reported disability.

CONCLUSION

Optimal exercise programs for knee OA should have one aim and focus on improving aerobic capacity, quadriceps muscle strength, or lower extremity performance. For best results, the program should be supervised and carried out 3 times a week. Such programs have a similar effect regardless of patient characteristics, including radiographic severity and baseline pain.

Anaerobic capacity of amateur mountain bikers during the first half of the competition season

Sustained aerobic exercise not only affects the rate of force development but also decreases peak power development. The aim of this study was to investigate whether anaerobic power of amateur mountain bikers changes during the first half of the competition season. Eight trained cyclists (mean ± SE: age: 22.0 ±0.5 years; height: 174.6 ± 0.9 cm; weight: 70.7 ± 2.6 kg) were subjected to an ergocycle incremental exercise test and to the Wingate test on two occasions: before, and in the middle of the season. After the incremental exercise test the excess post-exercise oxygen consumption was measured during 5-min recovery. Blood lactate concentration was measured in the 4th min after the Wingate test. Maximum oxygen uptake increased from 60.0 ± 1.5 ml min^-1 kg^-1 at the beginning of the season to 65.2 ± 1.4 ml min^-1 kg^-1 (P < 0.05) in the season. Neither of the mechanical variables of the Wingate test nor excess post-exercise oxygen consumption values were significantly different in these two measurements. However, blood lactate concentration was significantly higher (P < 0.001) in season (11.0 ± 0.5 mM) than before the season (8.6 ± 0.4 mM). It is concluded that: 1) despite the increase of cyclists’ maximum oxygen uptake during the competition season their anaerobic power did not change; 2) blood lactate concentration measured at the 4th min after the Wingate test does not properly reflect training-induced changes in energy metabolism.

Exercise-induced AMPK activation does not interfere with muscle hypertrophy in response to resistance training in men

As aerobic exercise (AE) may interfere with adaptations to resistance exercise (RE), this study explored acute and chronic responses to consecutive AE (∼45 min cycling) and RE (4 × 7 maximal knee extensions) vs. RE only. Ten men performed acute unilateral AE + RE interspersed by 15 min recovery. The contralateral leg was subjected to RE. This exercise paradigm was then implemented in a 5-wk training program. Protein phosphorylation, gene expression, and glycogen content were assessed in biopsies obtained from the vastus lateralis muscle of both legs immediately before and 3 h after acute RE. Quadriceps muscle size and in vivo torque were measured, and muscle samples were analyzed for citrate synthase activity and glycogen concentration, before and after training. Acute AE reduced glycogen content (32%; P < 0.05) and increased ( P < 0.05) phosphorylation of AMPK (1.5-fold) and rpS6 (1.3-fold). Phosphorylation of p70S6K and 4E-BP1 remained unchanged. Myostatin gene expression was downregulated after acute AE + RE but not RE. Muscle size showed greater ( P < 0.05) increase after AE + RE (6%) than RE (3%) training. Citrate synthase activity (18%) and endurance performance (22%) increased ( P < 0.05) after AE + RE but not RE. While training increased ( P < 0.05) in vivo muscle strength in both legs, normalized and concentric torque increased after RE only. Thus AE activates AMPK, reduces glycogen stores, and impairs the progression of concentric force, yet muscle hypertrophic responses to chronic RE training appear not to be compromised.

Beyond muscle hypertrophy: why dietary protein is important for endurance athletes

Recovery from the demands of daily training is an essential element of a scientifically based periodized program whose twin goals are to maximize training adaptation and enhance performance. Prolonged endurance training sessions induce substantial metabolic perturbations in skeletal muscle, including the depletion of endogenous fuels and damage/disruption to muscle and body proteins. Therefore, increasing nutrient availability (i.e., carbohydrate and protein) in the post-training recovery period is important to replenish substrate stores and facilitate repair and remodelling of skeletal muscle. It is well accepted that protein ingestion following resistance-based exercise increases rates of skeletal muscle protein synthesis and potentiates gains in muscle mass and strength. To date, however, little attention has focused on the ability of dietary protein to enhance skeletal muscle remodelling and stimulate adaptations that promote an endurance phenotype. The purpose of this review is to critically discuss the results of recent studies that have examined the role of dietary protein for the endurance athlete. Our primary aim is to consider the results from contemporary investigations that have advanced our knowledge of how the manipulation of dietary protein (i.e., amount, type, and timing of ingestion) can facilitate muscle remodelling by promoting muscle protein synthesis. We focus on the role of protein in facilitating optimal recovery from, and promoting adaptations to strenuous endurance-based training.

Cytokine mRNA expression responses to resistance, aerobic, and concurrent exercise in sedentary middle-aged men

Concurrent resistance and aerobic exercise (CE) is recommended to ageing populations, though is postulated to induce diminished acute molecular responses. Given that contraction-induced cytokine mRNA expression reportedly mediates remunerative postexercise molecular responses, it is necessary to determine whether cytokine mRNA expression may be diminished after CE. Eight middle-aged men (age, 53.3 ±1.8 years; body mass index, 29.4 ± 1.4 kg·m−2) randomly completed (balanced for completion order) 8 × 8 leg extensions at 70% maximal strength (RE), 40 min of cycling at 55% of peak aerobic workload (AE), or (workload-matched) 50% RE and 50% AE (CE). Muscle (vastus lateralis) was obtained pre-exercise, and at 1 h and 4 h postexercise, and analyzed for changes of glycogen concentration, tumor necrosis factor (TNF)α, TNF receptor-1 and -2 (TNF-R1 and TNF-R2, respectively), interleukin (IL)-6, IL-6R, IL-1β, and IL-1 receptor-antagonist (IL-1ra). All exercise modes upregulated cytokine mRNA expression at 1 h postexercise comparably (TNFα, TNF-R1, TNF-R2, IL-1β, IL-6) (p < 0.05). Expression remained elevated at 4 h after RE and AE (p < 0.05), though returned to pre-exercise levels after CE (p > 0.05). Moreover, AE and RE upregulated IL-1β and IL-1ra expression, whereas CE upregulated IL-1β expression only (p < 0.05). Only AE reduced muscle glycogen concentration (p < 0.05), whilst upregulating receptor expression the greatest; though, IL-6R expression remained unchanged after all modes (p > 0.05). In conclusion, in middle-aged men, all modes induced commensurate cytokine mRNA expression at 1 h postexercise; however, only CE resulted in ameliorated expression at 4 h postexercise. Whether the RE or AE components of CE are independently or cumulatively sufficient to upregulate cytokine responses, or whether they collectively inhibit cytokine mRNA expression, remains to be determined.

Biomechanical adaptations of mice cortical bone submitted to three different exercise modalities

Objective

To compare the adaptive effects of three non-weight bearing exercise on bone mechanical properties.

Methods

24 male Balb/c mice (22-25g), were randomly divided into four groups (n=6): sedentary group (S); swimming group (N) which performed sessions five times per week for 60 min progressively; resistance group (R), which performed climbing exercise with progressive load, three times per week; and combined group (C), which performed the same protocols aforementioned being three times a week according to N protocol and two times a week the R protocol during eight weeks. Biomechanical tests, load until failure and stiffness evaluation of shinbone was performed after animals have been sacrificed.

Results

Stiffness values were statistically higher only in the isolated modalities groups (N and R, 41.68 ± 10.43 and 41.21 ± 11.38 N/mm, respectively) compared with the S group (28.48 ± 7.34 N/mm). However, taking into consideration the final body mass, relative values, there was no difference in the biomechanical tests among the groups.

Conclusion

Data from the present investigation demonstrated a favorable influence of muscle contraction in lower impact isolated exercise modalities on absolute stiffness values, i.e.groups N and R, whereas the combined group (C) did not present any statistical significant difference compared to sedentary group. Level of Evidence II, Prospective Comparative Study.

Molecular mechanisms of muscle plasticity with exercise

The skeletal muscle phenotype is subject to considerable malleability depending on use. Low-intensity endurance type exercise leads to qualitative changes of muscle tissue characterized mainly by an increase in structures supporting oxygen delivery and consumption. High-load strength-type exercise leads to growth of muscle fibers dominated by an increase in contractile proteins. In low-intensity exercise, stress-induced signaling leads to transcriptional upregulation of a multitude of genes with Ca(2+) signaling and the energy status of the muscle cells sensed through AMPK being major input determinants. Several parallel signaling pathways converge on the transcriptional co-activator PGC-1α, perceived as being the coordinator of much of the transcriptional and posttranscriptional processes. High-load training is dominated by a translational upregulation controlled by mTOR mainly influenced by an insulin/growth factor-dependent signaling cascade as well as mechanical and nutritional cues. Exercise-induced muscle growth is further supported by DNA recruitment through activation and incorporation of satellite cells. Crucial nodes of strength and endurance exercise signaling networks are shared making these training modes interdependent. Robustness of exercise-related signaling is the consequence of signaling being multiple parallel with feed-back and feed-forward control over single and multiple signaling levels. We currently have a good descriptive understanding of the molecular mechanisms controlling muscle phenotypic plasticity. We lack understanding of the precise interactions among partners of signaling networks and accordingly models to predict signaling outcome of entire networks. A major current challenge is to verify and apply available knowledge gained in model systems to predict human phenotypic plasticity.

Genomics and genetics in the biology of adaptation to exercise

This article is devoted to the role of genetic variation and gene-exercise interactions in the biology of adaptation to exercise. There is evidence from genetic epidemiology research that DNA sequence differences contribute to human variation in physical activity level, cardiorespiratory fitness in the untrained state, cardiovascular and metabolic response to acute exercise, and responsiveness to regular exercise. Methodological and technological advances have made it possible to undertake the molecular dissection of the genetic component of complex, multifactorial traits, such as those of interest to exercise biology, in terms of tissue expression profile, genes, and allelic variants. The evidence from animal models and human studies is considered. Data on candidate genes, genome-wide linkage results, genome-wide association findings, expression arrays, and combinations of these approaches are reviewed. Combining transcriptomic and genomic technologies has been shown to be more powerful as evidenced by the development of a recent molecular predictor of the ability to increase VO2max with exercise training. For exercise as a behavior and physiological fitness as a state to be major players in public health policies will require that the role of human individuality and the influence of DNA sequence differences be understood. Likewise, progress in the use of exercise in therapeutic medicine will depend to a large extent on our ability to identify the favorable responders for given physiological properties to a given exercise regimen.

Nonlinear exercise training in advanced chronic obstructive pulmonary disease is superior to traditional exercise training. A randomized trial

RATIONALE

The optimal exercise training intensity and strategy for individualized exercise training in chronic obstructive pulmonary disease (COPD) is not clear.

OBJECTIVES

This study compares the effects of nonlinear periodized exercise (NLPE) training used in athletes to traditional endurance and progressive resistance (EPR) training in patients with severe COPD.

METHODS

A total of 110 patients with severe COPD (FEV1 32% predicted) were randomized to EPR or NLPE. Exercise training was performed three times per week for 10 weeks. The primary outcomes were cycling endurance time and health-related quality of life using the Chronic Respiratory Questionnaire. The difference in change between EPR and NLPE was assessed using linear mixed-effects modeling.

MEASUREMENTS AND MAIN RESULTS

NLPE resulted in significantly greater improvements in cycling endurance time compared with EPR. The difference in change was +300.6 seconds (95% confidence interval [CI] = 197.2-404.2 s; P < 0.001). NLPE also resulted in significantly greater improvements in all domains of the Chronic Respiratory Questionnaire compared with EPR, ranging from +0.48 (95% CI = 0.19-0.78) for the domain, emotions, to +0.96 (95% CI = 0.57-1.35) for dyspnea.

CONCLUSIONS

NLPE results in greater improvements in cycle endurance and health-related quality of life in patients with severe COPD than traditional training methods. Clinical trial registered with www.trialregister.nl (The Netherlands Trial Register; NTR 1045).

Optimizing strength training for running and cycling endurance performance: A review

Here we report on the effect of combining endurance training with heavy or explosive strength training on endurance performance in endurance-trained runners and cyclists. Running economy is improved by performing combined endurance training with either heavy or explosive strength training. However, heavy strength training is recommended for improving cycling economy. Equivocal findings exist regarding the effects on power output or velocity at the lactate threshold. Concurrent endurance and heavy strength training can increase running speed and power output at VO2max (Vmax and Wmax, respectively) or time to exhaustion at Vmax and Wmax. Combining endurance training with either explosive or heavy strength training can improve running performance, while there is most compelling evidence of an additive effect on cycling performance when heavy strength training is used. It is suggested that the improved endurance performance may relate to delayed activation of less efficient type II fibers, improved neuromuscular efficiency, conversion of fast-twitch type IIX fibers into more fatigue-resistant type IIA fibers, or improved musculo-tendinous stiffness.

Resistance exercise induced mTORC1 signaling is not impaired by subsequent endurance exercise in human skeletal muscle

The current dogma is that the muscle adaptation to resistance exercise is blunted when combined with endurance exercise. The suggested mechanism (based on rodent experiments) is that activation of adenosine monophosphate-activated protein kinase (AMPK) during endurance exercise impairs muscle growth through inhibition of the mechanistic target of rapamycin complex 1 (mTORC1). The purpose of this study was to investigate potential interference of endurance training on the signaling pathway of resistance training [mTORC1 phosphorylation of ribosomal protein S6 kinase 1 (S6K1)] in human muscle. Ten healthy and moderately trained male subjects performed on two separate occasions either acute high-intensity and high-volume resistance exercise (leg press, R) or R followed by 30 min of cycling (RE). Muscle biopsies were collected before and 1 and 3 h post resistance exercise. Phosphorylation of mTOR (Ser²⁴⁴⁸) increased 2-fold (P < 0.05) and that of S6K1 (Thr³⁸⁹) 14-fold (P < 0.05), with no difference between R and RE. Phosphorylation of eukaryotic elongation factor 2 (eEF2, Thr⁵⁶) was reduced ~70% during recovery in both trials (P < 0.05). An interesting finding was that phosphorylation of AMPK (Thr¹⁷²) and acetyl-CoA carboxylase (ACC, Ser⁷⁹) decreased ~30% and ~50%, respectively, 3 h postexercise (P < 0.05). Proliferator-activated receptor-γ coactivator-1 (PGC-1α) mRNA increased more after RE (6.5-fold) than after R (4-fold) (RE vs. R: P < 0.01) and was the only gene expressed differently between trials. These data show that the signaling of muscle growth through the mTORC1-S6K1 axis after heavy resistance exercise is not inhibited by subsequent endurance exercise. It is also suggested that prior activation of mTORC1 signaling may repress subsequent phosphorylation of AMPK.

A prospective study of weight training and risk of type 2 diabetes mellitus in men

BACKGROUND The role of weight training in the primary prevention of type 2 diabetes mellitus (T2DM) is largely unknown. METHODS To examine the association of weight training with risk of T2DM in US men and to assess the influence of combining weight training and aerobic exercise, we performed a prospective cohort study of 32 002 men from the Health Professionals Follow-up Study observed from 1990 to 2008. Weekly time spent on weight training and aerobic exercise (including brisk walking, jogging, running, bicycling, swimming, tennis, squash, and calisthenics/rowing) was obtained from questionnaires at baseline and biennially during follow-up. RESULTS During 508 332 person-years of follow-up (18 years), we documented 2278 new cases of T2DM. In multivariable-adjusted models, we observed a dose-response relationship between an increasing amount of time spent on weight training or aerobic exercise and lower risk of T2DM (P &lt; .001 for trend). Engaging in weight training or aerobic exercise for at least 150 minutes per week was independently associated with a lower risk of T2DM of 34% (95% CI, 7%-54%) and 52% (95% CI, 45%-58%), respectively. Men who engaged in aerobic exercise and weight training for at least 150 minutes per week had the greatest reduction in T2DM risk (59%; 95% CI, 39%-73%). CONCLUSIONS Weight training was associated with a significantly lower risk of T2DM, independent of aerobic exercise. Combined weight training and aerobic exercise conferred a greater benefit.

Attenuated increase in maximal force of rat medial gastrocnemius muscle after concurrent peak power and endurance training

Improvement of muscle peak power and oxidative capacity are generally presumed to be mutually exclusive. However, this may not be valid by using fibre type-specific recruitment. Since rat medial gastrocnemius muscle (GM) is composed of high and low oxidative compartments which are recruited task specifically, we hypothesised that the adaptive responses to peak power training were unaffected by additional endurance training. Thirty rats were subjected to either no training (control), peak power training (PT), or both peak power and endurance training (PET), which was performed on a treadmill 5 days per week for 6 weeks. Maximal running velocity increased 13.5% throughout the training and was similar in both training groups. Only after PT, GM maximal force was 10% higher than that of the control group. In the low oxidative compartment, mRNA levels of myostatin and MuRF-1 were higher after PT as compared to those of control and PET groups, respectively. Phospho-S6 ribosomal protein levels remained unchanged, suggesting that the elevated myostatin levels after PT did not inhibit mTOR signalling. In conclusion, even by using task-specific recruitment of the compartmentalized rat GM, additional endurance training interfered with the adaptive response of peak power training and attenuated the increase in maximal force after power training.

Effect of calcium intake on fat oxidation in adults: a meta-analysis of randomized, controlled trials

Calcium intake is likely to increase body fat loss during energy restriction. Part of this effect may be explained by increased fat oxidation in the presence of a similar energy balance, yet studies have not provided a conclusive answer. Therefore a meta-analysis was performed to determine whether chronic or acute high calcium intake increases fat oxidation. Randomized controlled trials of high calcium intake in human adults where measures of fat oxidation were taken were included. A random-effects meta-analysis was performed on outcomes expressed as standardized mean differences. Chronic high calcium intake increased fat oxidation by a standardized mean difference of 0.42 (95% confidence intervals: 0.14, 0.69; P= 0.003; estimated to correspond to an 11% increase), displaying low heterogeneity (I(2) = 18%), which was more prominent when habitual calcium intake was low (<700 mg d(-1) ). Acute high calcium intake increased fat oxidation by a standardized mean difference of 0.41 (0.04, 0.77; P = 0.03), with low heterogeneity (I(2) = 19%), yet sensitivity analysis revealed that this effect was relatively weak. In conclusion, chronic high calcium intake is likely to increase rates of fat oxidation. The effects of acute high calcium intake appear to point in the same direction, but further work is needed to permit a greater degree of certainty.

Adipokines promote lipotoxicity in human skeletal muscle cells

Studies have shown the implication of specific adipokines or fatty acids (FA) in the pathogenesis of insulin resistance. However, the interplay of adipokines with FA remains poorly understood. This study aimed to investigate the combined effects of adipokines and low concentrations of palmitic acid (PA, 100 µmol/l) on skeletal muscle metabolism. Human skeletal muscle cells were incubated with adipocyte-conditioned medium (CM), PA or PA+CM, and FA transporter and FA metabolism were analysed. CM-incubation increased CD36 level (1.8 fold) and PA-uptake (1.4 fold). However, only co-application of PA+CM resulted in profound lipid accumulation (5.3 fold), 60% reduction of PA-oxidation and 3.5 fold increased diacylglycerol content. Our results support a novel role for adipokines in the pathogenesis of T2D by increasing the lipotoxic potential of PA, notably of low concentrations. This implies an increased lipotoxic risk already at an early stage of weight gain, when lipolysis has not yet contributed to increased plasma free FA levels.

High-Intensity Interval Training

High-intensity interval training (HIT) is characterized by intermittent periods of work and rest and may include work bouts lasting seconds to minutes. HIT has typically been applied to older, diseased, and at-risk populations using longer work intervals (2-4 minutes), whereas more recent definitions of HIT include work intervals of 30 to 60 s. Both traditional endurance training (TET) and HIT exert a peripheral affect increasing the capacity of muscle cells to oxidize substrate via signaling cascades that support the activation of transcription factors that orchestrate the coexpression of nuclear and mitochondrial genes, with HIT triggering these benefits following minutes of training. With 1 exception, reports of central adaptations (eg, increased stroke volume) have been based on longer work intervals (eg, 4 minutes). Recent investigations have tied HIT to increased lipolysis and enhanced insulin sensitivity. HIT favors the activation of oxidative as opposed to hypertrophic pathways. Although the length of the work interval may need to be adjusted to fit the needs and capacity of the participant, HIT should be considered as an alternative to TET for older adults with the expectation that it requires less time to execute, yet promotes peripheral and perhaps central adaptations.