Neuromuscular adaptations to concurrent strength and endurance training

PURPOSE: The purpose of this study was to examine muscle morphological and neural activation adaptations resulting from the interaction between concurrent strength and endurance training. METHODS: Thirty sedentary healthy male subjects were randomly assigned to one of three training groups that performed 10 wk of 3-d x wk(-1) high-intensity strength training (S), cycle endurance training (E), or concurrent strength and endurance training (CC). Strength, quadriceps-muscle biopsies, computed tomography scans at mid-thigh, and surface electromyogram (EMG) assessments were made before and after training. RESULTS: S and CC groups demonstrated similar increases (P < 0.0001) in both thigh extensor (12 and 14%) and flexor/adductor (7 and 6%) muscle areas. Type II myofiber areas similarly increased (P < 0.002) in both S (24%) and CC (28%) groups, whereas the increase (P < 0.004) in Type I area with S training (19%) was also similar to the nonsignificant (P = 0.041) increase with CC training (13%). Significant increases (P < 0.005) in maximal isometric knee-extension torque were accompanied by nonsignificant (P 0.38) in the EMG/torque relation across 20 to 100% maximal voluntary contractions occurred in any group. A small 3% increase (P < 0.01) in thigh extensor area was the only change in any of the above variables with E training. CONCLUSIONS: Findings indicate 3-d x wk(-1) concurrent performance of both strength and endurance training does not impair adaptations in strength, muscle hypertrophy, and neural activation induced by strength training alone. Results provide a physiological basis to support several performance studies that consistently indicate 3-d x wk(-1) concurrent training does not impair strength development over the short term.     

Physiological adaptations to concurrent endurance training and low velocity resistance training

This study investigated the effects of concurrent endurances and low velocity resistance training (LVR) on measures of strength and aerobic endurance. One group (ES) performed concurrent endurance training 3 days a week and LVR training on alternate days, 3 days a week for 12 weeks. The other group (S) performed only LVR training 3 days a week for 12 weeks without any endurance training. Measurements and increases in training volume were made every three weeks in both groups. Group ES exhibited increases in submaximal exercise responses after 3, 9 and 12 weeks (p less than 0.05). Knee extension peak torque and total work as well as cross-sectional area of quadriceps femoris were significantly increased after 6 and 9 weeks of training in both groups. These findings indicate that no significant differences in strength gains were observed between subjects performing concurrent endurance and resistance training or resistance training only. However, the time-course of adaptations between groups was somewhat different.     

Neuromuscular and hormonal adaptations during strength and power training. A review

Increases in muscular strength among initially untrained subjects are relatively easily attained taking place during the earlier weeks of strength training mainly due to neural adaptations with a gradually increasing contribution of hypertrophic factors as the training proceeds. Muscular strength development in strength athletes is much more limited and special attention should be given to high training loading intensity and to individual training programming. The magnitudes and the time courses of the neuromuscular adaptations in strength athletes may therefore differ from those among initially untrained subjects but the actual mechanisms of strength increase may be basically the same. The initial status of the athletes makes the process more complicated to follow and more difficult to substantiate. In strength athletes with a long training background and with a high training volume, the role of endogenous hormone balance may have increasing importance for strength development. During the most stressful training weeks of prolonged strength training the level of biologically active unbound testosterone as well as the balance between the androgenic-anabolic activity and the catabolizing effect of glucocorticoids may be of great importance for the trainability of muscular strength. These observations together with the findings about the specific effects of heavy resistance strength and power training on the neuromuscular performance may also have some implications for the more accurate determination of the trainability status of an individual athlete at a given time in order to optimize the training process.     

Skeletal muscle and hormonal adaptations to circuit weight training in untrained men

Twelve men either performed 10 weeks of timed circuit weight training 3 days week(-1) (CWT; n=8; X+/-SE; age=23.6+/-1.8 years), or were part of a sedentary control group (n=4; age=20.5+/-1.0 years). Significance was P<0.05 for all analyses. The CWT program significantly increased 1 repetition maximum (1 RM) strength for nine of 10 exercises (15-42%). Although no body composition measure significantly changed for the CWT group, low-to-moderate effect sizes were evident for body weight, lean body mass, and relative fat. CWT did not alter percent fiber type, but did increase cross-sectional areas for type IIA fibers (microm(2); pre=5988+/-323, post=7259+/-669). Relative (%) myosin heavy-chain (MHC) expression increased for MHC IIa (pre=42.5+/-2.7, post=50.1+/-2.6), and decreased for MHC IIb (pre=21.8+/-2.8, post=15.4+/-2.4) for the CWT group. Serum testosterone, cortisol, and the testosterone/cortisol ratio did not change at any time for the CWT group. None of the measured variables changed for the control group. These data indicate that for untrained subjects, CWT of the type used resulted in improved muscular strength and a tendency toward increased lean mass. Compared with other types of weight training, fewer adaptations of the muscle fibers were evident. This is likely due in part to the relatively low loads used with this type of resistance exercise.     

Neuromuscular adaptations and serum hormones in females during prolonged power training

Training-induced adaptations in the neuromuscular and endocrine systems were investigated in seven females during prolonged power type strength training. Great (p less than 0.05) changes occurred primarily during the earlier weeks of the 16-week training especially in the time of force production (from 161 +/- 107 to 93 +/- 65 ms to produce a 500 N force) and, correspondingly, in the average forces in the earlier positions of the (absolute) force-time curve of the leg extensor muscles. These changes were accompanied by significant (p less than 0.05) increases in the neural activation of the trained muscles in the earliest positions of the IEMG-time curve. Hypertrophic changes, as judged from muscle fibre area data of both FT and ST types, were only slight (ns.) during the entire training period. No statistically significant changes occurred during the training in mean concentrations of serum testosterone, free testosterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), cortisol, progesterone, estradiol (E2) or sex hormone-binding globulin (SHBG). However, the individual mean serum levels of both total and free testosterone correlated significantly (r = .81-.95, p less than 0.05-0.01) with the individual changes during the training in the time of force production and in the forces in the force-time curve of the trained muscles. The present results in female subjects indicate the important role of training-induced adaptations in the nervous system for muscular power development. In females testosterone may be of great importance for muscular power and/or strength development during prolonged training and an important indicator of the trainability of an individual.     

Association between endurance performance,oxidative stress,and antioxidant markers during a running training program in untrained men

Purpose

The aim of this study was to examine the associations between running performance variables, oxidative stress (OS) and antioxidant markers at pre- and post- endurance running training program in untrained men. A second aim was to verify the responses of the performance variables, OS marker malondialdehyde (MDA) and antioxidant markers antioxidant markers catalase (CAT) and superoxide dismutase (SOD), reduced glutathione (GSH) and oxidized (GSSG) after the endurance training program.

Methods

Fifteen untrained men performed 8 weeks of endurance running training. All assessments were performed at pre- and post-endurance training program. The performance variables peak running velocity (V_peak) and 5-km performance (t_5-km), the OS marker MDA and the antioxidant markers CAT, SOD, reduced GSH and oxidized GSSG were analyzed. Absolute and percent changes were calculated (change from pre- to post-training) for each variable. Associations were performed using the Pearson (r) or Spearman (rho) correlation coefficient.

Results

The highest and significant correlations occurred between performance variables and GSSG at post-training (rho?= ? 0.86 and 0.88, with V_peak and t_5-km, respectively). All other correlations were not significant. Furthermore, 8 weeks of endurance training improved performance and no significant differences were observed in the OS and antioxidant responses between pre- and post-training.

Conclusion

The correlations between running performance variables and OS and antioxidant markers at pre- and post-training in untrained men were not significant and expressive, except for the associations between GSSG and performance variables (V_peak and t_5-km), that were very large. In addition, the endurance training program improved performance and did not significantly change the OS and antioxidant markers in untrained men.

     

Effects of photobiomodulation associated with endurance running training on oxidative stress in untrained men

Purpose

This study examined the effects of photobiomodulation (PBM) associated with endurance running training on oxidative stress (OS) markers in untrained men.

Methods

Thirty untrained men distributed into a placebo group (PLA) or PBM group (PBMG) performed 8 weeks of running training, in which the PBMG had the LED application before all training sessions. The PBM was performed by LED application using an equipment with 56 diodes of red light (660 nm) and 48 diodes of infrared light (850 nm) with an energy dose of 60 J on each of the 5 points. The application was done in two regions of the quadriceps muscle, two regions of the biceps femoris, and one region of the gastrocnemius muscle in both legs. The assessments were performed at pre- and post-training, and the OS markers analyzed were malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH) and oxidized (GSSG).

Results

PBM associated with running training did not significantly affect the OS markers CAT, SOD, MDA, GSH, and reduced GSH/GSSG responses after training. GSSG levels decreased in the PBMG and increased in the PLA, with significant difference between the % change values (??13.5?±?30.3% vs. 56.3?±?83.4%; P?=?0.043).

Conclusions

Therefore, PBM associated with endurance running training did not significantly affect CAT, SOD, MDA, reduced GSH, and reduced GSH/GSSG ratio post-training; however, the GSSG increased in PLA group and decreased in PBMG, indicating a positive effect of the PBM in this marker of OS.

     

Effect of endurance training on cardiovascular response to static exercise performed with untrained muscles

Eighteen male volunteers (20-23 years) were submitted to 13 weeks of training consisting of 30 min of exercise (at 50%-75% VO2max) on a bicycle ergometer, performed three times a week. Every 4 weeks the heart rate (HR), blood pressure (BP), and systolic time interval (STI) responses to the static handgrip (at 30% MVC) were examined. Before and after 13 weeks of training echocardiograms were recorded in seven subjects at rest and during the handgrip. Significant decreases in HR and BP responses to static exercise were found already after 4 weeks of training. Resting STI and left ventricular dimensions were not affected by training, but during the static exercise the pre-ejection period (PEP) and isovolumic contraction time interval (ICT) at the corresponding HR were significantly shortened after 8 weeks of training. The values of echocardiographic indices of left ventricular function obtained during exercise after training did not differ significantly from those found before training. It is concluded that endurance training of moderate intensity improves cardiac function during static exercise performed with untrained muscles.     

Effects of resistance, endurance, and concurrent exercise on training outcomes in men

The specificity of training principle predicts that combining resistance and endurance training (concurrent training) could interfere with the maximum development of strength and endurance capacity that results from either type of training alone. PURPOSE: To determine whether endurance and resistance training performed concurrently produces different performance and physiologic responses compared with each type of training alone. METHODS: Untrained male volunteers were randomly assigned to one of three groups: endurance training (ET, N = 12); resistance training (RT, N = 13); and concurrent training (CT, N = 16). The following measurements were made on all subjects before and after 12 wk of training: weight, percent body fat, peak oxygen consumption (VO(2peak)), isokinetic peak torque and average power produced during single-leg flexion and extension at 60 and 180 degrees.s, one-repetition maximum (1RM) leg press, 1RM bench press, vertical jump height, and calculated jump power. RESULTS: Weight and lean body mass (LBM) increased significantly in the RT and CT groups (P < 0.05). Percent body fat was significantly decreased in the ET and CT groups. VO(2peak) was significantly improved only in the ET group. Peak torque during flexion and extension at 180 degrees.s(-1) increased in the RT group. Improvements in 1RM leg press and bench press were significant in all groups, but were significantly greater in the RT and CT compared to the ET group. Jump power improved significantly only in the RT group, and no group showed a significant change in vertical jump height. CONCLUSIONS: Concurrent training performed by young, healthy men does not interfere with strength development, but may hinder development of maximal aerobic capacity.     

Neuromuscular adaptations induced by adjacent joint training

Effects of resistance training are well known to be specific to tasks that are involved during training. However, it remains unclear whether neuromuscular adaptations are induced after adjacent joint training. This study examined the effects of hip flexion training on maximal and explosive knee extension strength and neuromuscular performance of the rectus femoris (RF , hip flexor, and knee extensor) compared with the effects of knee extension training. Thirty‐seven untrained young men were randomly assigned to hip flexion training, knee extension training, or a control group. Participants in the training groups completed 4 weeks of isometric hip flexion or knee extension training. Standardized differences in the mean change between the training groups and control group were interpreted as an effect size, and the substantial effect was assumed to be ≥0.20 of the between‐participant standard deviation at baseline. Both types of training resulted in substantial increases in maximal (hip flexion training group: 6.2% ± 10.1%, effect size = 0.25; knee extension training group: 20.8% ± 9.9%, effect size = 1.11) and explosive isometric knee extension torques and muscle thickness of the RF in the proximal and distal regions. Improvements in strength were accompanied by substantial enhancements in voluntary activation, which was determined using the twitch interpolation technique and RF activation. Differences in training effects on explosive torques and neural variables between the two training groups were trivial. Our findings indicate that hip flexion training results in substantial neuromuscular adaptations during knee extensions similar to those induced by knee extension training.     

Effects of intra-session concurrent endurance and strength training sequence on aerobic performance and capacity

Aim: To examine the effects of the sequencing order of individualised intermittent endurance training combined with muscular strengthening on aerobic performance and capacity. Methods: Forty eight male sport students (mean (SD) age 21.4 (1.3) years) were divided into five homogeneous groups according to their maximal aerobic speeds (vV^·O₂MAX). Four groups participated in various training programmes for 12 weeks (two sessions a week) as follows: E (n = 10), running endurance training; S (n = 9), strength circuit training; E+S (n = 10) and S+E (n = 10) combined the two programmes in a different order during the same training session. Group C (n = 9) served as a control. All the subjects were evaluated before (T0) and after (T1) the training period using four tests: (1) a 4 km time trial running test; (2) an incremental track test to estimate vV^·O₂MAX; (3) a time to exhaustion test (t_lim) at 100% vV^·O₂MAX; (4) a maximal cycling laboratory test to assess V^·O₂MAX. Results: Training produced significant improvements in performance and aerobic capacity in the 4 km time trial with interaction effect (p<0.001). The improvements were significantly higher for the E+S group than for the E, S+E, and S groups: 8.6%, 5.7%, 4.7%, and 2.5% for the 4 km test (p<0.05); 10.4%, 8.3%, 8.2%, and 1.6% for vV^·O₂MAX (p<0.01); 13.7%, 10.1%, 11.0%, and 6.4% for V^·O₂MAX (ml/kg^0.75/min) (p<0.05) respectively. Similar significant results were observed for t_lim and the second ventilatory threshold (%V^·O₂MAX). Conclusions: Circuit training immediately after individualised endurance training in the same session (E+S) produced greater improvement in the 4 km time trial and aerobic capacity than the opposite order or each of the training programmes performed separately.     

Oxidative stress responses in older men during endurance training and detraining

PURPOSE: Aging is associated with increased oxidative stress, whereas systematic exercise training has been shown to improve quality of life and functional performance of the aged. This study aimed to evaluate responses of selected markers of oxidative stress and antioxidant status in inactive older men during endurance training and detraining. METHODS: Nineteen older men (65-78 yr) were randomly assigned into either a control (C, N = 8) or an endurance-training (ET, N = 11, three training sessions per week, 16 wk, walking/jogging at 50-80% of HR(max)) group. Before, immediately posttraining, and after 4 months of detraining, subjects performed a progressive diagnostic treadmill test to exhaustion (GXT). Plasma samples, collected before and immediately post-GXT, were analyzed for malondialdehyde (MDA) and 3-nitrotyrosine (3-NT) levels, total antioxidant capacity (TAC), and glutathione peroxidase activity (GPX). RESULTS: ET caused a 40% increase in running time and a 20% increase in maximal oxygen consumption (VO(2max)) (P < 0.05). ET lowered MDA (9% at rest, P < 0.01; and 16% postexercise, P < 0.05) and 3-NT levels (20% postexercise, P < 0.05), whereas it increased TAC (6% at rest, P < 0.01; and 14% postexercise, P < 0.05) and GPX (12% postexercise, P < 0.05). However, detraining abolished these adaptations. CONCLUSIONS: ET may attenuate basal and exercise-induced lipid peroxidation and increase protection against oxidative stress by increasing TAC and GPX activity. However, training cessation may reverse these training-induced adaptations.     

Resistive training effects on strength and cardiovascular endurance in cardiac and coronary prone patients

Resistive training using heavy loads with few repetitions increases strength but does little to improve cardiovascular endurance. Circuit weight training, a form of resistive training using moderate loads with frequent repetitions, is used to improve both cardiovascular and strength fitness. Studies of circuit weight training in healthy adults and athletes have shown increases of 20-45% and cardiovascular improvement from 0 to 15%. An increasing number of exercise programs for cardiac and coronary prone populations have introduced circuit weight training. The few reported studies have shown that high risk patients can attain increases in fitness similar to those seen in healthy populations. Furthermore, the hemodynamic responses to circuit weight training suggest that it is a clinically safe and acceptable form of exercise.     

Central and peripheral cardiovascular adaptations during a maximal cycle exercise in boys and men

PURPOSE: Stroke volume response to exercise depends on changes in cardiac filling, intrinsic myocardial contractility, and left ventricular afterload. The purpose of this study was to compare these responses during an upright cycle test performed until exhaustion in children and adults. METHODS: Stroke volume, cardiac output (Doppler echocardiography), left ventricular dimensions (two-dimensional and time-movement echocardiography), as well as arterial pressure and systemic vascular resistance (SVR) were assessed in 17 boys (mean age, 11.7 +/- 0.6 yr) and 23 young adult men (mean age, 21.2 +/- 2.7 yr) having a similar aerobic potential. All variables were measured at the end of the resting period, during the final minute of each workload, and during the last minute of the test. RESULTS: No significant differences were obtained for stroke volume, cardiac output, and left ventricular dimensions when they were scaled to body surface area at rest and whatever the exercise intensity. However, arteriovenous oxygen uptake was higher and the SVR lower in the adults than in the children. CONCLUSION: The patterns of stroke volume, as well as its underlying mechanisms, were not age-related during an upright maximal exercise test. However, other studies are required to understand further the effect of pubertal status on the peripheral cardiovascular system.     

Metabolic adaptations to endurance training and nutrition strategies influencing performance

ABSTRACT

Endurance performance is the result of optimal training targeting cardiovascular, metabolic, and peripheral muscular adaptations and is coupled to effective nutrition strategies via the use of macronutrient manipulations surrounding training and potential supplementation with ergogenic aids. It is important to note that training and nutrition may differ according to the individual needs of the athlete and can markedly impact the physiological response to training. Herein, we discuss various aspects of endurance training adaptations, nutritional strategies and their contributions to towards performance.     

Effects of strength and endurance training on antioxidant enzyme gene expression and activity in middle-aged men

This study was aimed at investigating the effects of a 21-week period of progressive strength or endurance training on peripheral blood mononuclear cells (PBMC) antioxidant enzyme gene expression and activity in healthy middle-aged untrained men. Strength ( n =11) and endurance ( n =12) training were performed twice a week, including resistance exercises to activate all the main muscle groups or cycle-ergometer pedaling, respectively. mRNA levels of catalase, glutathione peroxidase (GPx), mitochondrial superoxide dismutase (MnSOD) and cytosolic superoxide dismutase (CuZnSOD) were increased after 21 weeks of strength training, while endurance training induced significant changes only in MnSOD and GPx mRNA levels. CuZnSOD protein content was significantly increased only in strength-trained subjects. The program of strength or endurance exercise training had no significant effects on the activity of any of the antioxidant enzymes. In conclusion, in a middle-aged population, 21 weeks of strength or endurance training was a sufficient stimulus to up-regulate mRNA levels of PBMC antioxidant enzymes, the strength training being a more optimal stimulus. However, the discrepancies between enzyme protein and mRNA levels suggest that the present systematic strength or endurance training period had no beneficial effects on enzymatic antioxidant defense mechanisms in previously untrained middle-aged men.     

Effects of concurrent endurance and strength training on running economy and .VO(2) kinetics

PURPOSE: It has been suggested that endurance training influences the running economy (CR) and the oxygen uptake (.VO(2)) kinetics in heavy exercise by accelerating the primary phase and attenuating the .VO(2) slow component. However, the effects of heavy weight training (HWT) in combination with endurance training remain unclear. The purpose of this study was to examine the influence of a concurrent HWT+endurance training on CR and the .VO(2) kinetics in endurance athletes. METHODS: Fifteen triathletes were assigned to endurance+strength (ES) or endurance-only (E) training for 14 wk. The training program was similar, except ES performed two HWT sessions a week. Before and after the training period, the subjects performed 1) an incremental field running test for determination of .VO(2max) and the velocity associated (V(.VO2max)), the second ventilatory threshold (VT(2)); 2) a 3000-m run at constant velocity, calculated to require 25% of the difference between .VO(2max) and VT(2), to determine CR and the characteristics of the VO(2) kinetics; 3) maximal hopping tests to determine maximal mechanical power and lower-limb stiffness; 4) maximal concentric lower-limb strength measurements. RESULTS: After the training period, maximal strength were increased (P < 0.01) in ES but remained unchanged in E. Hopping power decreased in E (P < 0.05). After training, economy (P < 0.05) and hopping power (P < 0.001) were greater in ES than in E. .VO(2max), leg hopping stiffness and the .VO(2) kinetics were not significantly affected by training either in ES or E. CONCLUSION: Additional HWT led to improved maximal strength and running economy with no significant effects on the .VO(2) kinetics pattern in heavy exercise.