The effects of replacing a portion of endurance training by explosive strength training on performance in trained cyclists

To investigate the effects of replacing a portion of endurance training by strength training on exercise performance, 14 competitive cyclists were divided into an experimental (E; n=6) and a control (C; n=8) group. Both groups received a training program of 9 weeks. The total training volume for both groups was the same [E: 8.8 (1.1) h/week; C: 8.9 (1.7) h/week], but 37% of training for E consisted of explosive-type strength training, whilst C received endurance training only. Simulated time trial performance (TT), short-term performance (STP), maximal workload ( ) and gross (GE) and delta efficiency (DE) were measured before, after 4 weeks and at the end of the training program (9 weeks). No significant group-by-training effects for the markers of endurance performance (TT and ) were found after 9 weeks, although after 4 weeks, these markers had only increased (P<0.05) in E. STP decreased (P<0.05) in C, whereas no changes were observed in E. For DE, a significant group-by-training interaction (P<0.05) was found, and for GE the group-by-training interaction was not significant. It is concluded that replacing a portion of endurance training by explosive strength training prevents a decrease in STP without compromising gains in endurance performance of trained cyclists. Electronic Publication     

Training-induced changes in neuromuscular performance under voluntary and reflex conditions

Summary To investigate training-induced changes in neuromuscular performance under voluntary and reflex contractions, 11 male subjects went through heavy resistance (high loads of 70–120% of one maximum repetition) and 10 male subjects through explosive type (low loads with high contraction velocities) strength training three times a week for 24 weeks. A large increase (13.9%,p<0.01) in voluntary unilateral maximal knee extension strength with only slight and insignificant changes in time of isometric force production were observed during heavy resistance strength training. Explosive type strength training resulted in a small insignificant increase in maximal strength but in considerable shortening (p<0.05) in the time of force production. A significant increase (p<0.05) noted in the averaged maximal integrated electromyogram (IEMG) of the knee extensors during heavy resistance strength training correlated (p<0.01) with the increase in maximal strength. No changes were noted during training in reflex time components, but significant decreases (p<0.05) occurred in the peak-to-peak amplitudes of the reflex electromyograms (EMG) in both groups. The individual changes during training in the reflex EMG/force ratio were related (p<0.01) to the respective changes in IEMG/force ratio in voluntary contractions. The present observations support the concept of specificity of training, and suggest that specific training-induced adaptations in the neuromuscular system may be responsible for these changes in performance.     

Cardiovascular and muscular adaptations to combined endurance and strength training in elderly women

Twenty-one women aged 60–75 years were examined to determine whether combined endurance and strength training resulted in greater increase in peak oxygen consumption, sub-maximal time to fatigue, cardiac output, stroke volume, and leg extension load when compared to endurance training alone. Subjects in both the endurance training (E) and endurance and strength (E & S) groups trained 3 days a week, for 12 weeks, at an intensity of 70–80% V˙O ₂ peak for 30 min on a cycle ergometer. Subjects in the E & S groups also used resistance equipment to train the knee extensors. The workload for resistance training was based on an initial assessment of 10 repetitions maximum (10 RM), with 80% of that value used for training, three times weekly. Peak oxygen consumption increased to an average of 24.8 and 29.9% in the E and E & S groups, respectively, with no difference between groups. Subjects in the E & S and E groups significantly increased sub-maximal endurance time by 396 and 165%, respectively. Cardiac output, stroke volume, and arteriovenous oxygen difference at 80% peak V˙O ₂ were unchanged by either of the training methods. A needle biopsy was taken from the vastus lateralis before and after 12 weeks of training. Chi-square analysis of fibre area data showed an increase in the frequency of larger type I fibres in the post-training data from the E & S group, but an increase in the frequency of smaller fibres in the E group post-training; however, mean fibre area was not significantly changed by training. These data suggest that greater improvements in sub-maximal time to fatigue and strength is achieved when resistance training is added to an aerobic training programme in healthy elderly women.     

Seasonal fluctuations of selected physiological characteristics of elite alpine skiers

The effects of heavy resistance training and jumping exercise were examined during the 1989–1990 season in 12 international level alpine skiers. The athletes were tested before, during, immediately after training and during the period off training (June, July, October 1989, April 1990). Their mechanical behaviour was investigated using firstly squat jumps performed without (SJ) or with low extra loads (20 kg, SJ_20kg) and high extra loads (equivalent to body mass on the shoulders, SJ_bm) and secondly 15–30 s continuous jumping. These tests allowed the assessment of explosive dynamic strength production (SJ and SJ_20kg), slow dynamic strength (SJ_bm) and maximal mechanical power (continuous jumping). The training adopted resulted in specific changes in neuromuscular performance; in fact all the variables studied showed a significant improvement (P<0.01) from the beginning compared to the end of training. The range of improvement was between 55.4% (SJ_bm) and 12.5% (average power during 15-s continuous jumping). The enhancement of SJ had become significant by July. Surprisingly, even when no strength or jumping training was performed during the competition period (November-April), no deterioration in the neuromuscular performance was observed, there being no significant difference between the test values obtained in October 1989 and April 1990. It was concluded that the demanding competition programme of alpine skiers may provide a training stimulus adequate to maintain the neuromuscular improvement induced by training throughout the competition season.     

Effect of explosive type strength training on isometric force- and relaxation-time, electromyographic and muscle fibre characteristics of leg extensor muscles

To investigate the influence of explosive type strength training on isometric force- and relaxation-time and on electromyographic and muscle fibre characteristics of human skeletal muscle, 10 male subjects went through progressive training which included primarily jumping exercises without extra load and with light extra weights three times a week for 24 weeks. Specific training-induced changes in force-time curve were observed and demonstrated by great (P less than 0.05-0.01) improvements in in parameters of fast force production and by a minor (P less than 0.05) increase in maximal force. The continuous increases in fast force production during the entire training were accompanied by and correlated with the increases (P less than 0.05) in average IEMG-time curve and with the increase (P less than 0.05) in the FT:ST muscle fibre area ratio. The percentage of FT fibres of the muscle correlated (P less than 0.05) with the improvement of average force-time curve during the training. The increase in maximal force was accompanied by significant (P less than 0.05) increases in maximum IEMGs of the trained muscles. However, the hypertrophic changes, as judged from the anthropometric and muscle fibre area data, were only slight during the training. It can be concluded that in training for fast force production considerable neural and selective muscular adaptations may occur to explain the improvement in performance, but that genetic factors may determine the ultimate potential of the trainability of this aspect of the neuromuscular performance.     

Effect of strenuous strength training on the Na-K pump concentration in skeletal muscle of well-trained men

This study examined how strenuous strength training affected the Na-K pump concentration in the knee extensor muscle of well-trained men and whether leg muscle strength and endurance was related to the pump concentration. First, the pump concentration, taken as ³H-ouabain binding, was measured in top alpine skiers since strength training is important to them. Second, well-trained subjects carried out strenuous eccentric resistance training either 1, 2, or 3 times · week⁻¹ for 3 months. The Na-K pump concentration, the maximal muscle strength in a full squat lift (one repetition maximum, 1 RM), and the muscle endurance, taken as the number of full squat lifts of a mass of 70% of the 1 RM load, were measured before and after the training period. The mean pump concentration of the alpine skiers was 425 (SEM 11) nmol · kg⁻¹ wet muscle mass. The subjects in part two increased their maximal strength in a dose-dependent manner. The muscle endurance increased for all subjects but independently of the training programme. From a mean starting value of 356 (SEM 6) nmol · kg⁻¹ the mean Na-K pump concentration increased by 54 (SEM 15) nmol · kg⁻¹ (+15%, P < 0.001) when the results for all subjects were pooled. The effect was larger for those who had trained twice a week than for those who had trained only once a week (P=0.025), suggesting that the effect of strength training depended on the amount of training carried out. The muscle strength and endurance were not related to the pump concentration, suggesting that the pumping power of this enzyme did not limit the performance during heavy lifting. However, the individual improvements in the endurance test during the training period correlated with the individual changes in the pump concentration (r _Spearman=0.5; P=0.01) which could mean that a common factor both increases the pump concentration and makes the muscles more adapted to repeated heavy lifting. Accepted: 8 August 2000     

Effects of combined strength and sprint training on regulation of muscle contraction at the whole-muscle and single-fibre levels in elite master sprinters

Aim: This study aims at examining the effects of progressive strength and sprint training on regulation of muscle contraction at the whole‐muscle and single‐fibre levels in older sprint‐trained athletes. Methods: Eleven men (52–78 years) were randomized to a training (EX, n = 7) or control (CTRL, n = 4) group. EX participated in a 20‐week programme that combined sprint training with heavy and explosive strength exercises, while CTRL maintained their usual run‐based training schedules. Results: EX improved maximal isometric and dynamic leg strength, explosive jump performance and force production in running. Specific tension and maximum shortening velocity of single fibres from the vastus lateralis were not altered in EX or CTRL. Fibre type and myosin heavy chain isoform distributions remained unchanged in the two groups. There was a general increase in fibre areas in EX, but this was significant only in IIa fibres. The 10% increase in squat jump in EX was accompanied by a 9% increase in the integrated EMG (iEMG) of the leg extensors but the 21–40% increases in isometric and dynamic strength were not paralleled by changes in iEMG. Conclusion: Adding strength training stimulus to the training programme improved maximal, explosive and sport‐specific force production in elite master sprinters. These improvements were primarily related to hypertrophic muscular adaptations.     

Strength training effects on physical performance and serum hormones in young soccer players

To determine the effects of simultaneous explosive strength and soccer training in young men, 8 experimental (S) and 11 control (C) players, aged 17.2 (0.6) years, were tested before and after an 11-week training period with respect to the load-vertical jumping curve [loads of 0–70 kg (counter-movement jump CMJ0–70)], 5- and 15-m sprint performances, submaximal running endurance and basal serum concentrations of testosterone, free testosterone and cortisol. In the S group, the 11-week training resulted in significant increases in the low-force portion of the load-vertical jumping curve (5–14% in CMJ0–30, P<0.01) and in resting serum total testosterone concentrations (7.5%, P<0.05), whereas no changes were observed in sprint running performance, blood lactate during submaximal running, resting serum cortisol and resting serum free testosterone concentrations. In the C group, no changes were observed during the experimental period. In the S group, the changes in CMJ0 correlated (P<0.05–0.01) with the changes in the 5-m (r=0.86) and 15-m (r=0.92) sprints, whereas the changes in CMJ40 correlated negatively with the changes in the testosterone:cortisol ratio (r=–0.84, –0.92, respectively, P<0.05). These data indicate that young trained soccer players with low initial strength levels can increase explosive strength by adding low-frequency, low-intensity explosive-type strength training. The inverse correlations observed between changes in CMJ40 and changes in the testosterone:cortisol ratio suggest that a transient drop in this ratio below 45% cannot always be interpreted as a sign of overstrain or neuroendocrine dysfunction.An erratum to this article can be found at     

Changes in neuromuscular performance and muscle fiber characteristics of elite power athletes self-administering androgenic and anabolic steroids

The influence of androgenic-anabolic steroid-induced changes in measures of body composition, muscle fiber characteristics and various aspects of the neuromuscular performance of the leg extensor muscles was investigated in five experimental and six control power athletes during the 24-week programmed strength training followed by the additional six week training without hormone drugs. The mean values of the dosages of self-administration during the 24-week period were 31.0 +/- 14.3 mg/day for anabolic steroids (methandienone, stanozolol, nandrolone) and 178.4 +/- 82.7 mg/week for testosterone. During the 24-week hormone period the experimental group gained in fat-free weight (p less than 0.01) and in the mean muscle fiber areas (p less than 0.01) of the vastus lateralis muscle while the corresponding gains in the control group were minor (NS). The increases of maximal isometric force in the experimental and control groups were 14.7% (p less than 0.01) and 6.1% (NS), respectively, and the values obtained in average load-vertical jumping height curves were improved significantly (p less than 0.05) only in the experimental group. Increases of 18.2% (p less than 0.001) and 12.9% (p less than 0.01) took place in the squat lift in the experimental and control groups, respectively. Both groups demonstrated similar (p less than 0.05) improvements in isometric fast force production. During the additional six week programmed training without hormone drugs significant (p less than 0.05) increases were observed in the experimental group in addition to maximal isometric force and the squat-lift but also in isometric fast force production, while the corresponding changes in the control group were minor (NS). It is suggested that strength training in combination with administration of androgenic-anabolic steroids causes improvements in selected neuromuscular parameters. These changes may be greater than those of caused by the strength training alone.     

High volume of endurance training impairs adaptations to 12 weeks of strength training in well-trained endurance athletes

The purpose of the present study was to compare the effect of 12 weeks of strength training combined with a large volume of endurance training with the effect of strength training alone on the strength training adaptations. Well-trained cyclists with no strength training experience performed heavy strength training twice a week in addition to a high volume of endurance training during a 12-week preparatory period (S + E; n = 11). A group of non-strength trained individuals performed the same strength training as S + E, but without added endurance training (S; n = 7). Thigh muscle cross-sectional area, 1 repetition maximum (1RM) in leg exercises, squat jump performance, and peak rate of force development (RFD) were measured. Following the intervention period, both S + E and S increased 1RM strength, thigh muscle cross-sectional area, and squat jump performance (p < 0.05), and the relative improvements in S were greater than in S + E (p < 0.05). S increased peak RFD while S + E did not, and this improvement was greater than in S + E (p < 0.05). To the best of our knowledge, this is the first controlled study to demonstrate that the strength training response on muscle hypertrophy, 1RM strength, squat jump performance, and peak RFD is attenuated in well-trained endurance athletes during a period of concurrent endurance training.     

The influence of extra load on the mechanical behavior of skeletal muscle

Summary Eleven international jumpers and throwers engaged in year round training were divided into experimental (n=6) and control (n=5) groups. The experimental group was tested before and after a 3 weeks simulated hypergravity period, and again 4 weeks after the hypergravity period. The high gravity condition was created by wearing a vest weighing about 13% of the subjects body weight. The vest was worn from morning to evening including the training sessions, and only removed during sleep. The daily training of all subjects consisted of classical weight training and jumping drills. No changes in the ordinary training program were allowed in the experimental group, except for the use of the vest. Vertical jumps, drop jumps and a 15 s continuous jumping test were used to measure the explosive power characteristics of the subjects. After the hypergravity period the experimental subjects demonstrated significant (5–10%, P<0.05–0.01) improvements in most of the variables studied: however, 4 weeks after cessation of the high gravity period they tended to return towards the starting values. No changes were observed in the results of the control group. The improvement observed in the experimental subjects was explained as fast adaptation to the simulated high gravity field. It is suggested that adaptation had occurred both in neuromuscular functions and in metabolic processes.Supported by grants from Italian Track and Field Association, the Central Sport Federation of Finland, and Ministry of Education (Finland)     

Block training periodization in alpine skiing: effects of 11-day HIT on VO2max and performance

Attempting to achieve the high diversity of training goals in modern competitive alpine skiing simultaneously can be difficult and may lead to compromised overall adaptation. Therefore, we investigated the effect of block training periodization on maximal oxygen consumption (VO_2max) and parameters of exercise performance in elite junior alpine skiers. Six female and 15 male athletes were assigned to high-intensity interval (IT, N = 13) or control training groups (CT, N = 8). IT performed 15 high-intensity aerobic interval (HIT) sessions in 11 days. Sessions were 4 × 4 min at 90–95% of maximal heart rate separated by 3-min recovery periods. CT continued their conventionally mixed training, containing endurance and strength sessions. Before and 7 days after training, subjects performed a ramp incremental test followed by a high-intensity time-to-exhaustion (tlim) test both on a cycle ergometer, a 90-s high-box jump test as well as countermovement (CMJ) and squat jumps (SJ) on a force plate. IT significantly improved relative VO_2max by 6.0% (P < 0.01; male +7.5%, female +2.1%), relative peak power output by 5.5% (P < 0.01) and power output at ventilatory threshold 2 by 9.6% (P < 0.01). No changes occurred for these measures in CT. tlim remained unchanged in both groups. High-box jump performance was significantly improved in males of IT only (4.9%, P < 0.05). Jump peak power (CMJ −4.8%, SJ −4.1%; P < 0.01), but not height decreased in IT only. For competitive alpine skiers, block periodization of HIT offers a promising way to efficiently improve VO_2max and performance. Compromised explosive jump performance might be associated with persisting muscle fatigue.     

Effect of concurrent strength and endurance training on skeletal muscle properties and hormone concentrations in humans

The purpose of this study was to investigate the effect of concurrent strength and endurance training on strength, endurance, endocrine status and muscle fibre properties. A total of 45 male and female subjects were randomly assigned to one of four groups; strength training only (S), endurance training only (E), concurrent strength and endurance training (SE), or a control group (C). Groups S and E trained 3 days a week and the SE group trained 6 days a week for 12 weeks. Tests were made before and after 6 and 12 weeks of training. There was a similar increase in maximal oxygen consumption (V˙O_{2 max}) in both groups E and SE (P < 0.05). Leg press and knee extension one repetition maximum (1 RM) was increased in groups S and SE (P < 0.05) but the gains in knee extension 1 RM were greater for group S compared to all other groups (P < 0.05). Types I and II muscle fibre area increased after 6 and 12 weeks of strength training and after 12 weeks of combined training in type II fibres only (P < 0.05). Groups SE and E had an increase in succinate dehydrogenase activity and group E had a decrease in adenosine triphosphatase after 12 weeks of training (P < 0.05). A significant increase in capillary per fibre ratio was noted after 12 weeks of training in group SE. No changes were observed in testosterone, human growth hormone or sex hormone binding globulin concentrations for any group but there was a greater urinary cortisol concentration in the women of group SE and decrease in the men of group E after 12 weeks of training (P < 0.05). These findings would support the contention that combined strength and endurance training can suppress some of the adaptations to strength training and augment some aspects of capillarization in skeletal muscle. Accepted: 10 November 1998     

Neuromuscular adaptations during concurrent strength and endurance training versus strength training

The purpose of this study was to investigate effects of concurrent strength and endurance training (SE) (2 plus 2 days a week) versus strength training only (S) (2 days a week) in men [SE: n=11; 38 (5) years, S: n=16; 37 (5) years] over a training period of 21 weeks. The resistance training program addressed both maximal and explosive strength components. EMG, maximal isometric force, 1 RM strength, and rate of force development (RFD) of the leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris (QF) throughout the lengths of 4/15–12/15 (L _f) of the femur, muscle fibre proportion and areas of types I, IIa, and IIb of the vastus lateralis (VL), and maximal oxygen uptake (V˙O_2max) were evaluated. No changes occurred in strength during the 1-week control period, while after the 21-week training period increases of 21% (p<0.001) and 22% (p<0.001), and of 22% (p<0.001) and 21% (p<0.001) took place in the 1RM load and maximal isometric force in S and SE, respectively. Increases of 26% (p<0.05) and 29% (p<0.001) occurred in the maximum iEMG of the VL in S and SE, respectively. The CSA of the QF increased throughout the length of the QF (from 4/15 to 12/15 L _f) both in S (p<0.05–0.001) and SE (p<0.01–0.001). The mean fibre areas of types I, IIa and IIb increased after the training both in S (p<0.05 and 0.01) and SE (p<0.05 and p<0.01). S showed an increase in RFD (p<0.01), while no change occurred in SE. The average iEMG of the VL during the first 500 ms of the rapid isometric action increased (p<0.05–0.001) only in S. V˙O_2max increased by 18.5% (p<0.001) in SE. The present data do not support the concept of the universal nature of the interference effect in strength development and muscle hypertrophy when strength training is performed concurrently with endurance training, and the training volume is diluted by a longer period of time with a low frequency of training. However, the present results suggest that even the low-frequency concurrent strength and endurance training leads to interference in explosive strength development mediated in part by the limitations of rapid voluntary neural activation of the trained muscles. Electronic Publication     

Neuromuscular adaptations during short-term "normal" and reduced training periods in strength athletes

Neuromuscular adaptations during a 2-week "normal" strength training period followed by a 1-week reduced training period were investigated in ten strength athletes. No systematic changes were observed in the maximal voluntary neural activation (averaged integrated EMG) of leg extensor muscles, in the cross-sectional area (CSA) of the QF muscle or in maximal voluntary isometric force production characteristics of the leg extensor muscles in the whole subject sample over the entire strength training period of 3 weeks. However, significant increases were observed both in the maximal neural activation (p less than 0.05) and maximal force (from 4547 +/- 613 to 4923 +/- 901 N; p less than 0.05) of the muscles at the very end of the 1-week reduced training period in group A which consisted of five best strength athletes within the whole subject group. In group B consisting of five other athletes at a lower level no systematic changes were observed during the reduced training period. The present findings suggest that neuromuscular adaptations in strength athletes are very limited in magnitude at least during short term strength training. Maximal strength performance in highly trained strength athletes may be brought to the peak level not necessarily during "normal" strength training but more likely after some period of time with a reduced volume of training. The present observations support the concept of the periodization of training in highly trained strength athletes and indicate the important role of the nervous system in leading to the peak in their maximal strength.     

Neuromuscular adaptations during combined strength and endurance training in endurance runners: maximal versus explosive strength training or a mix of both

This study compared the effects of mixed maximal strength and explosive strength training with maximal strength training and explosive strength training combined with endurance training over an 8-week training intervention. Male subjects (age 21–45 years) were divided into three strength training groups, maximal (MAX, n = 11), explosive (EXP, 10) and mixed maximal and explosive (MIX, 9), and a circuit training control group, (CON, 7). Strength training one to two times a week was performed concurrently with endurance training three to four times a week. Significant increases in maximal dynamic strength (1RM), countermovement jump (CMJ), maximal muscle activation during 1RM in MAX and during CMJ in EXP, peak running speed (S _peak) and running speed at respiratory compensation threshold (RCT_speed) were observed in MAX, EXP and MIX. Maximal isometric strength and muscle activation, rate of force development (RFD), maximal oxygen uptake $ \left( {\dot{V}{\text{O}}_{2\max } } \right) $ and running economy (RE) at 10 and 12 km hr^?1 did not change significantly. No significant changes were observed in CON in maximal isometric strength, RFD, CMJ or muscle activation, and a significant decrease in 1RM was observed in the final 4 weeks of training. RE in CON did not change significantly, but significant increases were observed in S _peak, RCT_speed and $ \left( {\dot{V}{\text{O}}_{2\max } } \right). $ Low volume MAX, EXP and MIX strength training combined with higher volume endurance training over an 8-week intervention produced significant gains in strength, power and endurance performance measures of S _peak and RCT_speed, but no significant changes were observed between groups.     

Improving strength and postural control in young skiers: whole-body vibration versus equivalent resistance training

Context: Several groups have undertaken studies to evaluate the physiologic effects of whole-body vibration (WBV). However, the value of WBV in a training program remains unknown. Objective: To investigate whether a WBV program results in a better strength and postural control performance than an equivalent exercise program performed without vibration. Design: Randomized, controlled trial. Setting: Laboratory. Patients or Other Participants: Thirty-three Belgian competitive skiers (ages = 9-15 years). Intervention(s): Subjects were assigned to either the WBV group or the equivalent resistance (ER) group for 6 weeks of training at 3 times per week. Main Outcome Measure(s): Isokinetic plantar and dorsiflexion peak torque, isokinetic knee flexion and extension peak torque, explosive strength (high box test), and postural control were assessed before and after the training period. Results: Both training programs significantly improved isokinetic ankle and knee muscle strength and explosive strength. Moreover, the increases in explosive strength and in plantar-flexor strength at low speed were significantly higher in the WBV group than in the ER group after 6 weeks. However, neither WBV training nor ER training seemed to have an effect on postural control. Conclusions: A strength training program that includes WBV appears to have additive effects in young skiers compared with an equivalent program that does not include WBV. Therefore, our findings support the hypothesis that WBV training may be a beneficial supplementary training technique in strength programs for young athletes.     

Effects of isokinetic training of the knee extensors on high-intensity exercise performance and skeletal muscle buffering

Twenty-three subjects isokinetically trained the right and left quadriceps femoris, three times per week for 16 weeks; one group (n=13) trained at an angular velocity of 4.19 rad · s^–1 and a second group (n=10), at 1.05 rad · s^–1. A control group (n=10) performed no training. Isometric endurance time at 60% quadriceps maximum voluntary contraction (MVC), mean power output and work done (W) during all-out cycling, and the muscle buffer value (B) and carnosine concentration of biopsy samples from the vastus lateralis, were all assessed before and after training. The two training groups did not differ significantly from each other in their training response to any of these variables (P < 0.05). No significant difference in either 60% MVC endurance time or impulse [(endurance time × force) at 60% MVC] was observed for any group after the 16 week period (P > 0.05). However, the post-training increase (9%) in W during high-intensity cycling was greater in the training group than in the control group (P=0.04). NeitherB nor carnosine concentration showed any significant change following training (P=0.56 andP=0.37, respectively). It is concluded that 16 weeks of isokinetic training of the knee extensors enables subjects to do more work during high-intensity cycling. Although the precise adaptations responsible for the improved performance have yet to be identified, they are unlikely to include an increase inB.     

Endurance and neuromuscular changes in world-class level kayakers during a periodized training cycle

This study was undertaken to analyze changes in selected cardiovascular and neuromuscular variables in a group of elite kayakers across a 12-week periodized cycle of combined strength and endurance training. Eleven world-class level paddlers underwent a battery of tests and were assessed four times during the training cycle (T0, T1, T2, and T3). On each occasion subjects completed an incremental test to exhaustion on the kayak-ergometer to determine maximal oxygen uptake (VO_2max), second ventilatory threshold (VT2), peak blood lactate, paddling speed at VO_2max (PS_max) and at VT2 (PS_VT2), stroke rate at VO_2max and at VT2, heart rate at VO_2max and at VT2. One-repetition maximum (1RM) and mean velocity with 45% 1RM load (V _45%) were assessed in the bench press (BP) and prone bench pull (PBP) exercises. Anthropometric measurements (skinfold thicknesses and muscle girths) were also obtained. Training volume and exercise intensity were quantified for each of three training phases (P1, P2, and P3). Significant improvements in VO_2max (9.5%), VO₂ at VT2 (9.4%), PS_max (6.2%), PS_VT2 (4.4%), 1RM in BP (4.2%) and PBP (5.3%), V _45% in BP (14.4%) and PBP (10.0%) were observed from T0 to T3. A 12-week periodized strength and endurance program with special emphasis on prioritizing the sequential development of specific physical fitness components in each training phase (i.e. muscle hypertrophy and VT2 in P1, and maximal strength and aerobic power in P2) seems effective for improving both cardiovascular and neuromuscular markers of highly trained top-level athletes.     

有氧、无氧耐力训练对自主神经调节功能的影响及意义

为评价有氧、无氧耐力训练对自主神经功能的影响，提供健全、合理体育锻炼方案的理论依据，我们将41名健康男性青年，随机分为有氧耐力组和无氧耐力组，进行连续8周训练。分别于训练前、训练4周末、训练8周末进行5min短程心率变异性（HRV）频域、时域法分析。结果显示，与训练前比较，有氧耐力组迷走神经活动增强（HF、HFnu、RMSSD、PNN50，P值均〈0．05），交感神经活动里减弱趋势（LFnu），自主神经平衡表现为趋向迷走神经占优势（LF／HF）。HRV增大；无氧耐力组自主神经调节功能相对较稳定。本研究表明，有氧、无氧耐力训练对自主神经调节能力的影响取决于训练的负荷强度，与有氧训练相似，严格控制的适当强度的无氧耐力训练也可能有利于增强人体对环境的适应能力。