Serum hormones during prolonged training of neuromuscular performance

Summary The effects of a 24-weeks' progressive training of neuromuscular performance capacity on maximal strength and on hormone balance were investigated periodically in 21 male subjects during the course of the training and during a subsequent detraining period of 12 weeks. Great increases in maximal strength were noted during the first 20 weeks, followed by a plateau phase during the last 4 weeks of training. Testosterone/cortisol ratio increased during training. During the last 4 weeks of training changes in maximal strength correlated with the changes in testosterone/cortisol (P<0.01) and testosterone/SHBG (P<0.05) ratios. During detraining, correlative decreases were found between maximal strength and testosterone/cortisol ratio (P<0.05) as well as between the maximal strength and testosterone/SHBG ratio (P<0.05). No statistically significant changes were observed in the levels of serum estradiol, lutropin (LH), follitropin (FSH), prolactin, and somatotropin. The results suggest the importance of the balance between androgenic-anabolic activity and catabolizing effects of glucocorticoids during the course of vigorous strength training.     

Serum hormone concentrations during prolonged training in elite endurance-trained and strength-trained athletes

Summary A study of 1 year was performed on nine elite endurance-trained athletes (swimmers) and on eight elite strength-trained athletes (weightlifters) in order to examine the effects of training on the endocrine responses and on physical performance capacity. The measurements for the determination of serum hormone concentrations were performed at about 4-month intervals during the course of the year. The primary findings demonstrated that during the first and most intensive training period of the year in preparing for the primary competitions similar but statistically insignificant changes were observed in the concentrations of serum testosterone, free testosterone and cortisol in both the endurance-trained and strength-trained groups. After that period the changes in hormonal response over the year were infrequent and minor. A significant (p<0.01) decrease occurred in the strength-trained group in serum-free testosterone during the second period, which was characterized by the highest overall amount of training. Over the entire year the concentrations of serum hormones remained statistically unaltered in both groups. Slight but statistically insignificant increases of 1.2%±0.8% and 2.1%±5.1% were observed in the competitive performances over the year in the endurance-trained and strength-trained groups, respectively. The present findings in the two groups of elite athletes, who differed greatly with regard to the type of physiological loading, demonstrated that the overall hormonal responses both during the most intensive and during prolonged training periods were rather similar and the infrequent small changes remained well within the normal physiological range. The observations further indicate that the training may not have been too strenuous, with no noticeable symptoms of overtraining, and/or that it could have been in greater amount and/or of greater intensity, leading perhaps to greater improvement in competitive performance capacity.     

Neuromuscular adaptations and serum hormones in women during short-term intensive strength training

Summary The effects were investigated in ten women of intensive heavy resistance strength training lasting for 3 weeks on electromyographic (EMG) activity, muscle cross-sectional area (CSA) and voluntary force production characteristics of leg extensor muscles. Blood samples for the determinations of serum hormones were taken from five of the subjects. Significant increases occurred in the higher force portions of the isometric force-time curve with an increase of 9.7 (SD 8.4)% (P<0.01) in maximal peak force. An increase of 15.8 (SD 20.9)% (P<0.05) took place also in the maximal neural activation (integrated EMG) of the trained muscles, while an enlargement of 4.6 (SD 7.4)% (P<0.05) occurred in the CSA of the quadriceps femoris muscle. Maximal force per muscle CSA increased significantly (P<0.05). No statistically significant changes were observed during the training in the mean concentrations of serum testosterone, free testosterone, cortisol and sex hormone binding globulin (SHBG). The individual concentrations of serum testosterone: SHBG ratio correlated with the individual changes obtained during the training in the muscle CSA (r=0.99;P<0.01). The present findings in women indicated that the increases in maximal strength during short-term but intensive strength training were primarily due to the increased voluntary activation of the trained muscles, while muscle hypertrophy remained limited in magnitude. Large interindividual differences in women in serum testosterone concentrations could indicate corresponding differences in muscle hypertrophy and strength development even during a short-term but intensive strength training period.     

Serum thyroid hormones,thyrotropin and thyroxine binding globulin during prolonged strength training

Summary The effects of progressive strength training for 24 weeks on maximal strength and pituitary-thyroid function were studied in 21 males during the training and during the following detraining period of 12 weeks. Maximal strength increased greatly (p<0.001) in the first 20 weeks, followed by a plateau phase in the last 4 weeks of training. Maximal strength decreased greatly (p<0.001) during the detraining period. The concentrations of serum total (T₄) and free thyroxine (fT₄) decreased (p<0.05 and <0.01, respectively) during the training period and they rose to pretraining levels during the detraining period. During the most intense training phase (the last 4 weeks) there was a positive correlation between the changes in serum fT₄ concentrations and the changes in maximal force (r=0.56; p<0.01). No statistically significant changes occurred in the levels of serum triiodothyronine, thyrotropin or thyroxine binding gobulin. The results show that prolonged intensified strength training can slightly decrease the concentrations of serum total and free T₄. These small changes cannot have any clinical significance, and even their physiological significance may be only marginal.     

Neuromuscular and hormonal responses in elite athletes to two successive strength training sessions in one day

Summary Acute neuromuscular and endocrine adaptations to weight-lifting were investigated during two successive high intensity training sessions in the same day. Both the morning (I) (from 9.00 to 11.00 hours) and the afternoon (II) (from 15.00 hours to 17.00 hours) training sessions resulted in decreases in maximal isometric strength (p<0.01 and <0.05), shifts (worsening) in the force-time curve in the absolute scale (p<0.05 and ns.) and in decreases in the maximal integrated EMG (p<0.01 and <0.05) of the selected leg extensor muscles. Increases in serum total (p<0.05) and free testosterone (p<0.01) and in cortisol (p<0.01) concentrations were found during training session II. These were followed by decreases (p<0.001 andp<0.01 and ns.) in the levels of these hormones one hour after the termination of the session. The responses during the morning training session were different with regard to the decreases in serum total testosterone (p<0.05), free testosterone (ns.) and cortisol (p<0.05). Only slight changes were observed in the levels of luteinizing hormone and sex hormone-binding globulin during the training sessions. Increases (p<0.01) took place in somatotropin during both training sessions. The present findings suggest that high intensity strengthening exercises may result in acute adaptive responses in both the neuromuscular and endocrine systems. The diurnal variations may, however, partly mask the exercise-induced acute endocrinological adaptations in the morning. Recording of muscle activation and muscle strength and analysis of certain serum hormone concentrations with sufficient frequency during the training process may be useful in optimizing and controlling the contents of individual training sessions and the full training program.     

Serum hormones and physical performance capacity in young boy athletes during a 1-year training period

Summary Serum hormones and physical performance capacity in boy athletes (AG;n = 19) were investigated during a 1-year training period (between the ages of 11.6 and 12.6 years). Six young untrained boys served as the control group (CG). The mean serum testosterone concentration increased significantly in AG (P<0.05) following the training period from 2.92 nmol·l^–1, SD 1.04 to 5.81 nmol·l^–1, SD 1.33. Significant differences were not observed in the cortisol, sex hormone binding globulin and growth hormone levels during the follow-up period. The AG clearly increased speed (P<0.001), speed-strength (P<0.01-P<0.001) and anaerobic capacity (P<0.001) whereas CG had only slight increases (NS) in physical performance capacity during a 1-year period. During the last 6-month training period significant positive correlations (r=0.490–0.58;P<0.05 -P<0.01) were observed in AG between the relative changes in testosterone, testosterone: cortisol ratio and growth hormone and the relative performance change in speed, maximal isometric force and endurance, respectively. At the end of the period significant positive correlations were observed in all subjects between the level of testosterone and speed-strength (r=0.52–0.64;P<0.01 -P<0.001) and anaerobic capacity (r=0.49;P<0.05). It was concluded that an increase in anabolic activity with the synchronous training already has positive effects on trainability and physical performance capacity at an early stage in puberty.     

Serum cortisol concentration and testosterone to cortisol ratio in elite prepubescent male gymnasts during training

Summary Serum cortisol concentrations and testosterone: cortisol concentration ratios of eight prepubescent elite male gymnasts (mean age 10 years 11 months) and 11 controls (mean age 11 years 1 month) were examined during 5 consecutive training days. During this period, the gymnasts trained 3 h each day with moderate intensity mobility, strength and skill exercises while the controls were relatively sedentary. Blood samples were taken from all the boys in both groups before (1630 hours) and 30 min after (2000 hours) training on 4 days. Serum cortisol concentrations of the gymnasts were not significantly different from those of the controls throughout the experiment. Serum cortisol concentrations of both groups were significantly larger (P<0.05) at 1630 hours than at 2000 hours, indicating that cortisol secretion followed the typical adult circadian change, seemingly unaltered by training. However, there was a significant decrease (P<0.05) in the testosterone: cortisol ratio of the gymnasts when compared with controls from day 1 to day 3. After a rest on day 4 the testosterone: cortisol ratio of the gymnasts significantly increased (P<0.05) but the ratio of the control group also increased indicating that there may have been some day-to-day change by factor(s) other than training. The most obvious factor which may have accounted for the unresponsiveness of serum cortisol concentration to the gymnastics training was that the exercise intensity was too low. However, several days of the training seemed to reduce the anabolic to catabolic balance but further experiments are needed to confirm this finding.     

Serum hormones and strength development during strength training in middle-aged and elderly males and females

Effects of a 12-week progressive strength training period on serum concentrations of testosterone, Cortisol and sex-hormone-binding globulin (SHBG) as well as on strength development of the leg extensor muscles were investigated in nine middle-aged males (M50; range 44–57 years) and in nine middle-aged females (F50; range 43–54 years) as well as in 10 elderly males (M70; range 64–73 years) and in 11 elderly females (F70; range 66–73 years). Substantial increases took place in maximal isometric strength during the 12-week training period both in M50 (from 2834 ±452 to 3941 ±772 N; P < 0.001) and in F50 (from 2627±725 to 3488± 1017 N; P < 0.001) as well as in M70 (from 2591 ±736 to 3075±845N; P < 0.01) and in F70 (from 1816 ± 427 to 2483 ±408 N; P< 0.001). The relative increases in strength during the 12-week training period did not differ significantly between the groups. However, during the last 4 weeks of the training none of the groups demonstrated further increases in strength but it actually decreased in F50 (P < 0.05), M70 (P < 0.01) and in F70 (P < 0.05). No systematic changes were observed during the training in the mean concentrations of serum total testosterone, free testosterone, Cortisol, and SHBG, nor in testosterone/ Cortisol and testosterone/SHBG ratios. However, the individual levels of serum testosterone and testosterone/cortisol ratio and the individual changes in strength during the last four most intensive training weeks of the 12-week period were in significant positive linear correlation in F70 (r = 0.57; P < 0.05) and in M70 (r = 0.61; P < 0.05). The present findings demonstrate that considerable gains may take place in strength during progressive strength training both in middle-aged and elderly people. The findings also point out the importance of the anabolic hormonal level for the trainability of muscle strength of an individual during prolonged strength training especially in elderly males and females. This indicates a need to plan strength training programmes carefully with regard for to the overall volume and the length of each training period to optimize the training process in elderly people both in preventive purposes and in rehabilitation.     

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     

Hormonal adaptations and modelled responses in elite weightlifters during 6 weeks of training

Summary The concentrations of serum testosterone, sex-hormone-binding-globulin (SHBG) and luteinizing hormone (LH) were examined throughout 1-year of training in six elite weightlifters. A systems model, providing an estimation of fatigue and fitness, was applied to records of training volume and performance levels in clean and jerk. The analysis focused on a 6-week training period during which blood samples were taken at 2-week intervals. A 4-week period of intensive training (period I) could be distinguished from the following 2-week period of reduced training (period II). During period I, decreases in serum testosterone (P<0.05) and increases in serum LH concentrations (P<0.01) were observed; a significant correlation (r=0.90,P<0.05) was also observed between the changes in serum LH concentration and in estimated fitness. The magnitude of LH response was not related to the change in serum androgens. On the other hand, the change in testosterone: SHBG ratio during period II was significantly correlated (r=0.97,P<0.01) to the LH variations during period I. These finding suggested that the LH response indicated that the decrease in testosterone concentration was not primarily due to a dysfunction of the hypothalamic-pituitary system control, and that the fatigue/fitness status of an athlete could have influenced the LH response to the decreased testosterone concentration. The negative effect of training on hormonal balance could have been amplified by its influence on the hypothalamic-pituitary axis. A decrease in physiological stress would thus have been necessary for the completion of the effect of LH release on androgenic activity.     

优秀青少年男子篮球运动员腰腹屈伸肌群生物力学特征

背景：目前,等速测试系统在评定各专项运动员肌肉功能的应用越来越受到重视,但运用等速肌力测试技术研究优秀青少年男子篮球运动员腰腹肌力特征的报道较少。 目的：研究优秀青少年男子篮球运动员腰腹屈伸肌群生物力学特征,为篮球项目的腰腹力量训练、科学选材和预防腰腹损伤提供依据。 方法：采用Cybex-Norm等速肌力测试系统,对广州男子篮球队运动员18人测定腰腹屈伸肌群在慢速60(°)/s和快速180(°)/s的肌力和做功情况。 结果与结论：受试者腰腹屈伸肌群的峰力矩和相对峰力矩在同一测试速度下,伸肌群大于屈肌群(P < 0.01);腰腹屈伸肌群的峰力矩、相对峰力矩、总功均随着测试速度的增加呈减小趋势(P < 0.05),伸肌群的峰力矩和相对峰力矩减少更显著(P < 0.01);腰腹屈伸肌群的相对功率随着测试速度的增加而呈上升趋势(P < 0.01);外线球员腰腹屈伸肌群各测试指标成绩优于内线球员;在等速向心收缩时,随测试速度加快,腰腹屈伸肌群的峰力矩屈伸比呈递减趋势,躯干稳定性减弱。结果提示,优秀青少年男子篮球运动员腰腹伸肌群肌力大于屈肌群;外线球员腰腹屈伸肌群的肌力优于内线球员;等速快速运动时,腰腹屈伸肌群力量减小,腰腹关节屈伸肌力平衡性减弱,应加强青少年男子篮球运动员腰腹核心肌群快速力量训练。   中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

青少年男子体操运动员主要关节的等速肌力特征

BACKGROUND: The gymnastic skill training of juveniles tends to be scientific and systematic, such as confirming the strength characteristics of joints and muscles and implementing training program pertinently based on the scientific diagnostic method. OBJECTIVE: To explore the isokinetic muscle strength characteristics of the trunk, hips and knees in juvenile male gymnasts. METHODS: Sixteen juvenile male gymnasts who were active athletes in Liaoning province were enrolled. ISOMED2000 isokinetic muscle strength test system was used to detect the muscle strength, and the test speed of trunk set as 30, 60 and 180 (°)/s, while 60, 180 and 300 (°)/s for the hips and knees. RESULTS AND CONCLUSION: At 30, 60 and 180 (°)/s, the hamstring/quadriceps ratio of trunk were 91.36±1.25, 87.77±3.74 and 78.20±4.70, respectively. At 60, 180 and 300 (°)/s, the hamstring/quadriceps ratio of the left hip was 65.55±4.38, 66.92±3.22 and 68.18±2.82, while that of the right hip were 57.40±4.43, 65.73±1.07 and 64.15±5.55. Additionally, the left flexor strength was significantly higher than that of the right, while the right extensor strength was significantly higher than that of the left at 60 (°)/s (P < 0.05). At 60, 180 and 300 (°)/s, the hamstring/quadriceps ratio was 50.88±4.98, 54.75±4.51 and 58.80±7.93 for the left knee, and 51.55±4.30, 55.20±5.08 and 58.43±5.93 for the right knee. In three test speeds there were no significant differences in flexor and extensor strength between two sides (P > 0.05). These results indicate that the rapid strength of the back especially of the flexor is insufficient markedly, and the basic strength of the extensor is weak. The basic strength of the left flexor in the hip is large, the same as the right extensor; the rapid strength of flexor is weak, and imbalance in the muscle strength between two sides appears. Fortunately, the muscle strength of the knee between two sides achieves balance, but there is still a certain deficiency in the rapid strength of the left flexor and the basic strength of the extensor on both sides. 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Haematological and iron-related parameters of male endurance and strength trained athletes

Summary To obtain more information on the effects of long-lasting endurance and strength training on the constituents of the blood, several haematological and iron-related parameters were measured at rest in 39 male athletes from the Polish team who participated in the Olympics in Seoul in 1988. The athletes were divided into two groups: endurance-trained subjects (group E, cyclists, canoeists and rowers; n=22) and strength-trained subjects (group S, wrestlers and judo; n=17). The control group was composed of untrained male subjects (n=48). Blood samples were taken from an antecubital vein with the subject at rest for determinations of haemoglobin concentration ([Hb]), packed cell volume (PCV), erythrocyte (RBC) and reticulocyte count, plasma free haemoglobin concentration, haptoglobin concentration, serum iron, transferrin concentration and ferritin concentrations ([Ferr]); red blood cells were used for estimation of glutamato-oxalate transaminase (GOT) activity and free erythrocyte protoporphyrin concentration ([FEP]). The mean [Hb], PVC, RBC measured in the E athletes were significantly lower than in the control group but were comparable to those obtained in the S athletes. There were no significantly differences in the haematological indices [mean corpuscular volume (MCV), mean copuscular haemoglobin and mean corpuscular haemoglobin concentration] between the groups of athletes and the control group. A significant increase in reticulocytosis and GOT activity was observed in the endurance-trained athletes. No impairment of erythropoiesis was observed as indicated by several sensitive markers of haemoglobin formation (FEP, MCV and inspection of blood smears) in the athletes. The athletes from group E had mean serum [Ferr] below 50 g·l^–1 which was significantly lower than [Ferr] in the serum of subjects from the control group and the strength-trained athletes. The results of the present investigation showed that some haematological parameters and the iron status of the endurance athletes differed from the untrained subjects as well as the strength-trained athletes.     

Metabolic response of endurance athletes to training with added load

Summary Endurance athletes were divided into experimental (n=12) and control (n=12) groups to investigate the effects of extra-load training on energy metabolism during exercise. A vest weighing 9%–10% body weight was worn every day from morning to evening for 4 weeks including every (n=6) or every other (n=6) training session. After 4 weeks the control group had a lower blood lactate concentration during submaximal running, whereas the experimental group had significantly higher blood lactate and oxygen uptake (p<0.01–p<0.05), and a lower 2 mmol lactate threshold (p<0.05) and an increased blood lactate concentration after a short running test to exhaustion (p<0.05). Those experimental subjects (n=6) who used the added load during every training session had a lower 2 mmol lactate threshold, improved running time to exhaustion, improved vertical velocity when running up stairs and an increased during submaximal running after the added load period. It is concluded that the additional loading increased anaerobic metabolism in the leg muscles during submaximal and maximal exercise. An increased recruitment and adaptation of the fast twitch muscle fibres is suggested as the principal explanation for the observed changes.     

Changes in voluntary and electrically induced contractions during strength training and detraining

Summary To elucidate the changes in neuro-muscular function during strength training and detraining, five male subjects underwent progressive isotonic strength training of their calf muscles three times a week for 8 weeks with additional detraining for the same periods. Electrically evoked twitch contractions were induced in the triceps surae muscles of each subject every 4 weeks during the training and detraining periods. At the same time, maximal voluntary isometric contractions (MVC) and the maximal girth of the calf (MGC) were measured. During the training period, MVC increased significantly from 98.4 to 129.6 Nm (31.7%, P < 0.01) for the first 4 weeks of training but MGC showed little increase. Neither of the changes correlated with each other. Twitch contraction parameters, i.e. maximal twitch torque (P _t ), maximal rate of torque development (max dT/dt) and rate of relaxation (relax dT/dt) showed no statistical change. During detraining, on the contrary, a large and significant increase (22.5%, P < 0.01) was observed in max dTldt without any changes in P _t and relax dT/dt. The MVC/P _t showed both significant increases during training and decreases during detraining. Our data suggest that short term strength training as employed in the present study does not induce changes in the contractile properties of the muscle during training, but may significantly affect the rate of force development during the subsequent detraining period, indicating the possible existence of complex post-training muscle adaptation.     

EMG,muscle fibre and force production characteristics during a 1 year training period in elite weight-lifters

Summary The effects of a 1 year training period on 13 elite weight-lifters were investigated by periodical tests of electromyographic, muscle fibre and force production characteristics. A statistically non-significant increase of 3.5% in maximal isometric strength of the leg extensors, from 4841±1104 to 5010±1012 N, occured over the year. Individual changes in the high force portions of the force-velocity curve correlated (p<0.05–0.01) with changes in weight-lifting performance. Training months 5–8 were characterized by the lowest average training intensity (77.1+2.0%), and this resulted in a significant (p<0.05) decrease in maximal neural activation (IEMG) of the muscles, while the last four month period, with only a slightly higher average training intensity (79.1±3.0%), led to a significant (p<0.01) increase in maximum IEMG. Individual increases in training intensity between these two training periods correlated with individual increases both in muscular strength (p<0.05) and in the weight lifted in the clean & jerk (p<0.05). A non-significant increase of 3.9% in total mean muscle fibre area occurred over the year. The present findings demonstrate the limited potential for strength development in elite strength athletes, and suggest that the magnitudes and time courses of neural and hypertrophic adaptations in the neuromuscular system during their training may differ from those reported for previously untrained subjects. The findings additionally indicate the importance of training intensity for modifying training responses in elite strength athletes.     

Stroke volume response to progressive exercise in athletes engaged in different types of training

Summary Using the impedance cardiography method, heart rate ( _c) matched changes on indexed stroke volume (SI) and cardiac output (CI) were compared in subjects engaged in different types of training. The subjects consisted of untrained controls (C), volleyball players (VB) who spent about half of their training time (360 min · week^–1) doing anaerobic conditioning exercises and who had a maximal oxygen uptake ( ) 41% higher than the controls, and distance runners (D) who spent all their training time (366 min·week^–1) doing aerobic conditioning exercises and who had a 26% higher than VB. The subjects performed progressive submaximal cycle ergometer exercise (10 W·min^–1) up to _c of 150 beats·min^–1. In group C, SI had increased significantly (P<0.05) at _c of 90 beats·min^–1 ( + 32%) and maintained this difference up to 110 beats·min^–1, only to return to resting values on reaching 130 beats·min^–1 with no further changes. In group VB, SI peaked (+ 54%) at _c of 110 beats·min^–1, reaching a value significantly higher than that of group C, but decreased progressively to 22010 of the resting value on reaching 150 beats·min^–1. In group D, SI peaked at _c of 130 beats·min^–1 (+ 54%), reaching a value significantly higher than that of group VB, and showed no significant reduction with respect to this peak value on reaching 150 beats·min^–1. As a consequence, the mean CI increase per _c unit was progressively higher in VB than in C (+46%) and in D than in VB (+ 105%). It was concluded that thef _c value at which SI ceased to increase during incremental exercise was closely related to the endurance component in the training programme.     

Specificity of velocity in strength training

Summary Twenty-one male volunteers (ages 23–25 years) were tested pre- and post training for maximal knee extension power at five specific speeds (1.05, 2.09, 3.14, 4.19, and 5.24 rad·s⁻¹) with an isokinetic dynamometer. Subjects were assigned randomly to one of three experimental groups; group S, training at 1.05 rad·s⁻¹ (n=8), group I, training at 3.14 rad·s⁻¹ (n=8) or group F, training at 5.24 rad·s⁻¹ (n=5). Subjects trained the knee extensors by performing 10 maximal voluntary efforts in group S, 30 in group I and 50 in group F six times a week for 8 weeks. Though group S showed significant increases in power at all test speeds, the percent increment decreased with test speed from 24.8% at 1.05 rad·s⁻¹ to 8.6% at 5.24 rad·s⁻¹. Group I showed almost similar increment in power (18.5–22.4 at all test speeds except at 2.09 rad·s⁻¹ (15.4%). On the other hand, group F enhanced power only at faster test speeds (23.9% at 4.19 rad·s⁻¹ and 22.8% at 5.24 rad·s⁻¹).     

Effects of different strength training regimes on moment and power generation during dynamic knee extensions

This study examined the effect of different training regimes on moment and power generation during maximal knee extensions at low to very high extension velocities (0–1000°·s^–1 individual range). A group of 24 soccer players performed 12 weeks of progressively adjusted strength training of the knee extensors at either high resistance (HR,n=7), low resistance (LR,n=6), loaded kicking movements (FU,n=6), while one group served as controls (n=5). Moment and power generation of the knee extensors were determined before and after the training period with a nonisokinetic measuring method recently described. Following HR training, knee extension moment increased 9%–10% at knee angular velocities 0 (isometric) and 30° · s^–1 (P<0.05), peak moment increased 20% at 240–300°·s^–1 (P<0.05), while power generation increased 5%–29% at 240–480° · s^–1 (P<0.01). In addition, in the HR group maximal recorded power increased 45% (P<0.01). After FU training a 7%–13% increase in moment and power was observed at 30–180° · s^–1 (P<0.05). Following LR training, peak moment increased 9% at 120° · s^–1 (P<0.05). Improvements in knee extension moment and power were generally related to the angular velocities employed during training. However, as evaluated using the present measuring method, moment and power increased not only at very low but also at high knee angular velocities following the high-resistance strength training.     

Hypertrophy without increased isometric strength after weight training

Summary Eight men (20–23 years) weight trained 3 days week^–1 for 19 weeks. Training sessions consisted of six sets of a leg press exercise (simultaneous hip and knee extension and ankle plantar flexion) on a weight machine, the last three sets with the heaviest weight that could be used for 7–20 repetitions. In comparison to a control group (n = 6) only the trained group increased (P<0.01) weight lifting performance (heaviest weight lifted for one repetition, 29%), and left and right knee extensor cross-sectional area (CAT scanning and computerized planimetry, 11%, P<0.05). In contrast, training caused no increase in maximal voluntary isometric knee extension strength, electrically evoked knee extensor peak twitch torque, and knee extensor motor unit activation (interpolated twitch method). These data indicate that a moderate but significant amount of hypertrophy induced by weight training does not necessarily increase performance in an isometric strength task different from the training task but involving the same muscle group. The failure of evoked twitch torque to increase despite hypertrophy may further indicate that moderate hypertrophy in the early stage of strength training may not necessarily cause an increase in intrinsic muscle force generating capacity.