Physiological adaptations to velocity-controlled resistance training.

The force-velocity characteristics of skeletal muscle are such that maximal force is inversely related to the velocity of shortening. This relationship has been observed using isolated muscle preparations and intact muscle groups (e.g. knee extensors). Isokinetic dynamometry has revealed some specific physiological adaptations to different velocities of training: an increase in torque and power that are greater at or near the velocity of training; a transfer of torque gains to slower and faster angular velocities after intermediate velocity resistance training; increases in maximal oxygen consumption and cardiac output in response to circuit training; increases in anaerobic power output; changes in skeletal muscle size and changes in myofibrillar ATPase activity; and new applications for rehabilitation of muscular and ligamentous injuries, and post-coronary patients.     

Muscle imbalance in badminton athletes: preventive training programmes need to be designed

Sport Sciences for Health -     

Achilles tendon rupture in badminton.

The typical badminton player with an Achilles tendon rupture is 36 years old and, despite limbering up, is injured at the rear line in a sudden forward movement. He resumes work within three months and has a slight lack of dorsiflexion in the ankle as the main complication. Most patients resume badminton within one year, but some finish their sports career, mainly due to fear of a new injury. The investigation discusses predisposing factors and prophylactic measures.     

Physiological adjustments to intensive interval treadmill training

During a one month training period, eight active men, aged 23-35 years, completed sixteen 30 minute sessions of high intensity interval (5 second work bouts at 16.9 km/hr up 20-25% grade alternated with 10 second rest intervals) treadmill work. In this training period, O₂, _E and blood lactate in a 10 minute run at 12.9 km/hr on a level treadmill were unchanged but heart rate during this work decreased by an average of 9 beats/min. During a 4 minute interval work effort at the training intensity, blood lactate accumulation decreased by 40.4%. In exhausting work, mean values of O₂, _E and blood lactate increased by 6.2%, 8.2% and 31.6% respectively. Maximal heart rate decreased by an average of 4 beats/min. The average work production of the men in the training sessions improved by 64.5% from 28,160 kgm to 43,685 kgm. No significant improvements were observed in either a short sprint or a stair climbing test which assessed the ability to generate mechanical power from alactacid anaerobic sources. It was concluded that the training regime is an effective method of producing a high total work output in competitive athletes and results in improvements in aerobic power, glycolytic capacity and ability to tolerate the short duration interval work encountered in many games.     

Physiological profiles of young boys training in ballet.

In order to evaluate physiological characteristics in young male ballet dancers, 27 boys (aged 9 to 16 years) who participated in a boys' dance course during the Kuopio Dance and Music Festival in June 1988 were studied. In general, the boys had started dancing at the age of 8.6 years and had been training for 4.1 years. They had, on average, three dancing sessions per week and the mean time spent on dancing was four hours per week. In the study, some anthropometric measurements were taken, the maximal oxygen uptake (VO2 max) was measured by a cycle ergometer test and the explosive strength and the mechanical power of lower extremities were evaluated by a jumping test. The results indicate that boys who train in ballet are in general moderately lean, have relatively small body size and a high degree of flexibility. The younger boys especially have only moderate aerobic power, but both explosive strength and mechanical power in leg muscles are good in ballet trained boys.     

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.     

A new tool to measure training load in soccer training and match play

An accurate evaluation of training load is paramount for the planning and periodization of training. The aim of the present study was to evaluate the relationship between a new method to monitor training load in soccer (Visual Analogic Scale training load; VAS-TL), and two established heart rate-based methods (TRIMP and Edwards' method). 51 soccer players (age 15.6±0.3 years) answered 2 questions to assess perceived exertion and fatigue (VAS1-TL, and VAS2-TL) after training sessions and official matches. Performance in the Yo-Yo tests, VAS scores and heart rate of training sessions and matches, and match activity were analysed. We found significant correlations (r=0.60-0.72; p<0.05) between VAS-TL, TRIMP, and the Edwards' training load method, with the highest correlations achieved in the matches. Although the different methods to monitor training load were correlated with the distance covered during the match (r=0.53-0.78; p<0.05), only VAS1-TL was associated with high-intensity activities (r=0.43-0.54; p<0.05). The new VAS-based perceived exertion method to monitor training load is easy to apply and is sensitive to differences in positional role and physical capacity. Thus, the applied method may be used in addition to the usual training load methods, allowing for daily quantification of individual training load in soccer.     

Early effects of short-term aerobic training. Physiological responses to graded exercise

AIM: The aim of this study was to find out how early the moderate training effects appear and to check the hypothesis that familiarization with exercise protocol may contribute to an early physiological responses to training in previously sedentary subjects. METHODS: Twelve male, sedentary volunteers (22.0+/-0.7 yrs) were submitted to 3 weeks of a bicycle ergometer training, consisting of 45 min of exercise (at 70% VO(2)max), 3-4 times a week. The subjects performed 4 incremental exercise tests until volitional exhaustion: 2 before training (C1 and C2), and then after 1 (T1) and 3 (T3) weeks of training. During exercise HR, VO(2), electrical activity (EMG) of rectus femoris, biceps femoris, soleus and trapezius muscles were recorded and blood samples were taken for blood lactate (LA) determination. RESULTS: Already after 1 week of training HR decreased (p<0.05) with a further decline after 3 weeks the training (p<0.01). Maximal work load after 3 weeks of training increased to 277+/-10.4 W vs 250+/-9.5 W (p<0.05), VO(2)max achieved higher values than in C1 and C2 tests (p<0.05) and LA and EMG thresholds were elevated (p<0.05). CONCLUSION: A decrease in the resting and submaximal heart rate is the earliest effect of increased physical activity. Familiarization to exercise protocol decreased EMG of biceps femoris and soleus muscles during exercise, but did not influence that of rectus femoris muscle the most engaged during cycling.     

Physiological adaptations and analysis of training content in high school cross-country runners

The purposes of this study were to examine effects of a season of training on aerobic performance in cross-country distance runners and to analyze the training using subjective and objective techniques. Subjects averaged 184 minutes of running per week, with 45%, 24%, and 31% occurring in zones below, near, and above the heart rate (HR) corresponding to ventilatory threshold (VT(HR)), respectively (Zone 1: HR > 15 bpm below VT(HR); Zone 2: HR between Zone 1 and VT(HR); Zone 3: HR > VT(HR)). Maximal oxygen uptake (VO(2 max)) increased by 5.1%, 5-km race time by 46 seconds (3.7%), and 2-km time trial performance by 54 seconds (10.7%) from pre- to postseason. Results are similar to previous research demonstrating that short-term (< 3 months) endurance training elicits improvements in various physiological parameters. Findings were not consistent with previous research that suggests a discrepancy may exist between the runners' perceptions and the physiological effects of their training.     

Physiological response to circuit weight training in borderline hypertensive subjects

Male subjects (10 experimental, 16 control) with borderline hypertension (140/90 to 160/95 mm Hg) participated in a circuit weight training program for 9 wk to assess its efficacy and safety. Resting blood pressure and heart rate were measured under standardized conditions prior to and following each session and at several locations in the circuit. Subjects were assessed pre- and post-training. Upper and lower body strength increased 12.5 and 53% when assessed by one-repetition maximum lifts for bench press (57 to 64 kg) and leg press (134 to 205 kg), respectively. Total weight lifted per circuit increased 57% (4,374 to 6,866 kg). Lean body mass increased 2.2% (64.0 to 65.4 kg), skinfold thicknesses decreased, and other measures of body composition remained unchanged. Cardiovascular endurance as assessed by arm ergometry maximal oxygen uptake increased 21.1% (1.9 to 2.3 1 X min-1), and by 7.8% as assessed by treadmill maximal oxygen uptake (40.9 to 44.1 ml X kg-1 X min-1). Resting heart rate and systolic blood pressure did not change. Diastolic blood pressure fell from 95.8 to 91.3 mm Hg. All changes were significant to at least P less than 0.05. Thus, circuit weight training can elicit marked improvements in muscular strength and modest improvements in body composition and cardiorespiratory endurance. Circuit weight training does not exacerbate resting or exercise blood pressure and may have beneficial effects.     

Injuries in badminton

Though badminton is one of the most widely played sports in the world, it has received little sports medical interest. Based on the few existing studies on injuries in badminton, compared to other sports it is of relatively low risk and dominated by overuse injuries. The injury duration is relatively long, but only a few working days are lost. Anatomically, most injuries are localised to the foot and ankle. The single most frequent injuries are Achilles tendinitis and tennis elbow. Rupture of the Achilles tendon is a rare injury, which is typically seen in older recreational players. When the time of exposure is taken into account men are found to have a higher injury risk than women, and recreational players a higher injury risk than elite players. In contrast to most other sports the relative injury risk is higher during training than in competition. Based on suggested causes of injury and injury mechanisms, together with the known injury pattern in badminton the following preventive matters are suggested: (a) changes in the badminton shoe, towards a higher heel, with shock absorption and a stiffer anatomically fitting heel counter; (b) adjustment of the friction between the individual shoe-soles and playing surfaces; and (c) specific badminton training including stretching and strengthening of the triceps surae and the muscles involved in the internal and external rotation of the shoulder and elbow during the badminton strokes.     

Physiological consequences of U.S. Army Ranger training

PURPOSE: Soldiers are expected to maintain a high degree of physical readiness as operational demands can severely degrade performance capabilities. This study examined the physiological consequences of U.S. Army Ranger training on strength, power, body composition, and somatotrophic hormones. METHODS: In an intensive 8-wk military training course that included an average daily energy deficit of 1000 kcal.d, lower-body power output, maximal lifting strength, body composition, and serum concentrations of several somatotrophic hormones were measured in 50 male soldiers (24.6 +/- 4.4 y; 176.1 +/- 7.8 cm; 78.4 +/- 8.7 kg; 14.7 +/- 4.2% body fat) before and after the course. RESULTS: Vertical jump height (-16%), explosive power output (-21%), maximal lifting strength. (-20%), body mass (-13%), fat-free mass (-6%), and fat mass (-50%) declined (P < 0.05) after the training course. Circulating total testosterone and insulin-like growth factor-I (IGF-I) experienced significant (P < 0.05) declines, and cortisol was significantly increased. Lower-body power output, but not maximal lifting strength, correlated with changes in fat-free mass. IGF-I and cortisol, but not total testosterone, were correlated with losses of tissue mass. CONCLUSION: Lower-body power output, estimated from vertical jump height and body mass, is a sensitive and field expedient measure that can be used to assess the influence of caloric deficit on physical performance after 8 wk of U.S. Army Ranger training. With severe weight loss (>or=13% of body mass), IGF-I and cortisol correlate more closely with soft-tissue tissue adaptations than does testosterone.     

Physiological considerations in training young athletes

Healthy children evidence smaller values of cardiorespiratory function than adults, but these are in proportion to the smaller body size. At birth, the distribution of muscle fibres and the activity of enzymes in muscle are different from in adults, but these differences disappear at about age 6. On the other hand, muscle fibre thickness increases from birth to about 18 years of age and this is concurrent with increases in muscular strength. The increase in maximal oxygen consumption (VO2max) that accompanies growth and maturation in the human has been attributed in the main to appreciating muscle mass. During exercise, heart rate and cardiac output increase in the child as in the adult, but the heart rate in the child is greater and the stroke volume smaller. Furthermore, the arteriovenous difference in oxygen is greater in the exercising child than in the adult. Children also evidence a diminished blood pressure response to exercise. It seems that control of ventilation at exercise is the same in children as in adults, but exercise ventilation has been reported to be less efficient in the child. The young are less capable of regulating core temperature at exercise than adults and are more readily dehydrated. Very limited data suggest that muscle energy substrate storage and utilisation in children are such that they are less capable of anaerobic metabolism than adults. Generally, children respond to aerobic training as do adults, but such training in the first decade of life has been reported to have negligible effects. Blood lipid levels in children seem to be favourably influenced by persistent endurance activity. Ventilatory efficiency of children at exercise is augmented by aerobic training. Maximal values of ventilation and breathing frequency are increased in children and youth by endurance training. Conflicting data exist regarding the influence of training upon the child's vital capacity. Pulmonary diffusion capacity in well trained children has been seen to be greater than in untrained youngsters and many workers have reported increased VO2max as an outcome of endurance training. Limited data indicate that the nature of training may alter muscle fibre distribution in youthful athletes, and that muscle fibre hypertrophy can be induced in the young by means of strength and power training.(ABSTRACT TRUNCATED AT 400 WORDS)     

The application of principal component analysis to quantify technique in sports

Analyzing an athlete's “technique,” sport scientists often focus on preselected variables that quantify important aspects of movement. In contrast, coaches and practitioners typically describe movements in terms of basic postures and movement components using subjective and qualitative features. A challenge for sport scientists is finding an appropriate quantitative methodology that incorporates the holistic perspective of human observers. Using alpine ski racing as an example, this study explores principal component analysis (PCA) as a mathematical method to decompose a complex movement pattern into its main movement components. Ski racing movements were recorded by determining the three‐dimensional coordinates of 26 points on each skier which were subsequently interpreted as a 78‐dimensional posture vector at each time point. PCA was then used to determine the mean posture and principal movements (PM_k) carried out by the athletes. The first four PM_k contained 95.5 ± 0.5% of the variance in the posture vectors which quantified changes in body inclination, vertical or fore‐aft movement of the trunk, and distance between skis. In summary, calculating PM_k offered a data‐driven, quantitative, and objective method of analyzing human movement that is similar to how human observers such as coaches or ski instructors would describe the movement.     

A survey of badminton injuries.

A Badminton Injury Questionnaire (BIQ) was developed to survey the type and frequency of injuries that are likely to occur from playing competitive badminton. Two hundred and thirty-one players, ranging from club players to international champions, completed the survey which indicated an injury incidence rate of .09 and .14 injuries per person per year for male and female badminton players respectively. Badminton participation resulted in relatively few injuries, most of which were cramps, blisters, strains and sprains of the lower extremities and a surprisingly low incidence of tennis elbow.     

Physiological changes seen after six weeks sequence training.

Changes in body fat, cardiovascular endurance, muscular endurance, flexibility and strength were assessed in 22 women and 16 men after 6 weeks sequence training. It was found that two training sessions per week were sufficient to cause a significant increase in the majority of measurements made. The extent of the improvement in women was inversely related to the starting value, with most measurements, whereas this was not found in men. The measurements in this small group were comparable to those found in a large series in Canada, with the exception of the proportion of body fat which was lower in this UK series.     

An alternative whole-body marker set to accurately and reliably quantify joint kinematics during load carriage

Body armor covers anatomical landmarks that would otherwise be used to track trunk and pelvis movement in motion analysis. This study developed and evaluated a new marker set, and compared it to placing markers on the skin and over-top of body armor. In our method, pelvis and trunk motions were measured using a custom-built sacral and upper-back marker cluster, respectively. Joint angles and ranges of motion were determined while participants walked without and with body armor. Angles were obtained from the new marker set and compared against conventional marker sets placed on the skin or over-top the body armor. Bland-Altman analyses compared the agreement of kinematic parameters between marker sets, while joint angle waveforms were compared using inter-protocol coefficient of multiple correlations (CMCs). The intra- and inter-session similarities of joint angle waveforms from each marker set were also assessed using CMCs. There was a strong agreement between joint angles from the new marker set and markers placed directly on the skin at key anatomical landmarks. The agreement worsened with markers placed on top of body armor. Inter-protocol CMCs comparing markers on body armor to the new marker set were poor compared to CMCs between skin-mounted markers and the new marker set. Intra- and inter-session repeatability were higher for the new marker set compared to placing markers over-top of body armor. The new marker set provides a viable alternative for researchers to reliably measure trunk and pelvis motion when equipment, such as body armor, obscures marker placement.