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.

Optoelectronic measures in the analysis of running target shooting.

In this study, we examined the construct validity and practical significance of an optoelectronic shooting training system (Noptel ST 2000 Sport) for the technical analysis of running target shooting. A total of 37 male shooters of three different skill levels participated in the study. Principal component analysis revealed four common factors of 16 variables describing the aiming trajectory of the rifle barrel: (i) Holding area, (ii) Accuracy of aiming, (iii) Cleanness of triggering and (iv) Time on target. These factors were suggested to describe the essential components of running target shooting. According to the discriminant analysis, the shooters of various skill levels seemed to discriminate successfully into three groups when the aiming trajectory data were analysed. Finally, the aiming trajectory variables represented a 43% of the total variance in the shooting score. In summary, the present data indicated that the optoelectronic shooting training system had practical significance and supported the technical analysis of rifle barrel movement in running target shooting. A sub-set of variables, which reflect the essential information of running target shooting performance, were outlined for training and coaching purposes.

Effects of 12-week shooting training and mode of feedback on shooting scores among novice shooters.

The mode of feedback has been shown to have an effect on motor skill learning. This study investigated effects of an intensive 12-week shooting training period, and of the mode of feedback on scores in standing and running target shooting among 30 novices with limited shooting experience. They were divided into one control (no training) and three training groups. One out of the three training groups received only KR (knowledge of results) while the two other groups received KR+KP (knowledge of performance). One of the KR+KP groups received additional visual feedback (FB-II group), which included videos, graphic and written materials about kinematic and kinetic characteristics of their respective shooting techniques compared to performance of international level shooters. Each training group improved their scores in the running target shooting. There were no significant differences between the three training groups in improvements of sum scores (performance outcome). The current study showed that among novice shooters both KR alone and KR+KP improved running target shooting outcome, and that KR and KP together did not lead to a significantly better shooting performance than KR alone.

Neuromuscular functioning of athletes and non-athletes in the drop jump.

In many sports vertical jumping is important. This study compared neuromuscular functioning of the lower extremity muscles together with some kinetic and kinematic parameters before and during ground contact in drop jumps from two heights [0.4 m (DJ40) and 0.8 m (DJ80)] in 7 highly trained triple-jumpers and 11 physically active controls. The triple-jumpers jumped 32% higher in DJ40 and 34% higher in DJ80, had shorter braking and total contact times, and greater average and peak vertical ground reaction forces than the controls. In both drop jumps in the electromyogram pre-activity of the vastus lateralis and gastrocnemius muscles started earlier in the jumpers than in the controls. For the control group the increase in dropping height was associated with a decrease in the propulsion force, and resulted in more extended knee and ankle angles at touch down and more flexed angles at the deepest position than for the jumpers. All angular displacements for DJ80 were larger than for DJ40 in the control group. The triple jumpers and control subjects differed with respect to their neuromuscular functioning in the drop jump exercise and they responded in a different way to the increase in dropping height.

Reliability of variables in the kinematic analysis of spring hurdles.

The purpose of this study was to investigate the reliability of kinematic variables in spring hurdles and to find out how many trials are needed to achieve reliable data. Seven British National level athletes in sprint hurdles were videotaped and all eight trials of each athlete were digitized from two camera views to produce three dimensional coordinates. The reliability of 28 kinematic variables across eight trials ranged from 0.54 to 1.00 for females and from 0.00 to 0.99 for males. The number of trials needed to reach a certain reliability level was evaluated using Spearman-Brown prophecy formula, and in the worst case (horizontal velocity lost for males) 78 trials would be needed to reach 0.90 reliability. The results showed reasonably high reliability, and the values for the female trials were generally higher than the male trials. The relative height of the hurdles enforces a more demanding clearance for males that can lead to increased variation within the subjects and thus lowered reliability. Subsequently, the results indicate that often more than one trial is needed to provide accurate quantitative results of the technique.

Effects of oxygen fraction in inspired air on force production and electromyogram activity during ergometer rowing.

Six male rowers rowed maximally for 2500 m in ergometer tests during normoxia (fractional concentration of oxygen in inspired air, F(I)O2 0.209), in hyperoxia (F(I)O2 0.622) and in hypoxia (F(I)O2 0.158) in a randomized single-blind fashion. Oxygen consumption (VO2), force production of strokes as well as integrated electromyographs (iEMG) and mean power frequency (MPF) from seven muscles were measured in 500-m intervals. The iEMG signals from individual muscles were summed to represent overall electrical activity of these muscles (sum-iEMG). Maximal force of a stroke (Fmax) decreased from the 100% pre-exercise maximal value to 67 (SD 12)%, 63 (SD 15)% and 76 (SD 13)% (P < 0.05 to normoxia, ANOVA) and impulse to 78 (SD 4)%, 75 (SD 14)% and 84 (SD 7)% (P < 0.05) in normoxia, hypoxia and hyperoxia, respectively. A strong correlation between Fmax and VO2 was found in normoxia but not in hypoxia and hyperoxia. The mean sum-iEMG tended to be lower (P < 0.05) in hypoxia than in normoxia but hyperoxia had no significant effect on it. In general, F(I)O2 did not affect MPF of individual muscles. In conclusion, it was found that force output during ergometer rowing was impaired during hypoxia and improved during hyperoxia when compared with normoxia. Moreover, the changes in force output were only partly accompanied by changes in muscle electrical activity as sum-iEMG was affected by hypoxic but not by hyperoxic gas. The lack of a significant correlation between Fmax and VO2 during hypoxia and hyperoxia may suggest a partial uncoupling of these processes and the existence of other limiting factors in addition to VO2.

Physical loading and performance as predictors of back pain in healthy adults. A 5-year prospective study.

We investigated muscle strength, aerobic power, and occupational and leisure-time physical loading as predictors of back pain in a 5-year follow-up study. A cohort of 456 adults aged 25, 35, 45 and 55 years, free of back pain, participated in measurements of anthropometric characteristics, aerobic power and muscle strength characteristics at baseline. The subjects' levels and types of physical activity and occupational physical loading were also determined. At 5 years after the baseline examinations 356 of these subjects (78.1%) were reached by mail, and 262 of them (73.6%) properly completed and returned a questionnaire including a detailed back pain history for the 5 years following the baseline measurements. Of this number 56 subjects (21%) who reported back pain (> 30 on a scale from 0 to 100) and functional impairment during the 5-year follow-up composed the marked back pain group. Other subjects (n = 71, 27%) noting lesser symptoms were included in the mild back pain group; 135 subjects (52%) reported having had no back pain. The subjects with marked back pain were on average taller than the subjects without back pain, while no such difference was found in body mass. Heavy occupational musculoskeletal loading (P = 0.005) and high general occupational physical demands (P = 0.036) predicted future back pain. Leisure-time physical activity, aerobic power or muscle strength characteristics were not predictive of future back pain.

Effects of oxygen fraction in inspired air on rowing performance.

The present study examined the effect of oxygen fraction in inspired air (FIO2) on exercise performance and maximum oxygen consumption (VO2max). Six national level male rowers exercised three 2500-m all-out tests on a Concept II rowing ergometer. Each subject performed one test in normoxia (FIO2 20.9%), one in simulated hyperoxia (FIO2 62.2%) and one in simulated hypoxia (FIO2 15.8%) in a randomized single-blind fashion. The mean final rowing time was 2.3 +/- 0.9% (P < 0.01; 95% CI 1.4-3.2) shorter in hyperoxia and 5.3 +/- 1.8% (P < 0.01; 95% CI 3.1-7.5) longer in hypoxia when compared with normoxia. The effect of FIO2 on VO2max exceeded its effect on exercise performance as VO2max was 11.1 +/- 5.7% greater (P < 0.01; 95% CI 5.1-17.1) in hyperoxia and 15.5 +/- 3.2% smaller in hypoxia (P < 0.01; 95% CI 12.2-19.0) than in normoxia. Blood lactate concentration and O2 consumption per power unit (ml O2.W-1) failed to indicate statistically significant differences in anaerobic metabolism between normoxia and the other two conditions. These data suggest that there are other parameters besides those of energy metabolism that affect exercise performance as FIO2 is modified. These possible mechanisms are discussed in this paper.

Warm underwater water-jet massage improves recovery from intense physical exercise.

The effects of warm underwater water-jet massage on neuromuscular functioning, selected biochemical parameters (serum creatine kinase, lactic dehydrogenase, serum carbonic anhydrase, myoglobin, urine urea and creatinine) and muscle soreness were studied among 14 junior track and field athletes. Each subject spent, in a randomized order, two identical training weeks engaged in five strength/power training sessions lasting 3 days. The training weeks differed from each other only in respect of underwater water-jet massage treatments. These were used three times (20 min each) during the treatment week and not used during the control week. During the treatment week continuous jumping power decreased and ground contact time increased significantly less (P < 0.05) and serum myoglobin increased more than during the control week. It is suggested that underwater water-jet massage in connection with intense strength/power training increases the release of proteins from muscle tissue into the blood and enhances the maintenance of neuro-muscular performance capacity.

Forearm tremor in relation to selected physiological and body dimensional variables.

Interrelationships between forearm tremor and a number of body dimensional, muscle structure, muscular strength and training background variables were studied among 13 male students with athletic backgrounds. The subjects performed isometric dominant upper extremity elbow flexions with a 90 degrees joint angle and with the forearm held in a horizontal position. A freely hanging mass was attached via a strain gauge transducer, a metal chain and cuff to the forearm. An accelerometer attached to the cuff measured the vertical component of tremor. The power spectrum density function was calculated for a tremor acceleration signal and a bandwidth of 7-20 Hz was analysed in more detail. The right M. vastus lateralis was biopsed in order to determine the muscle fiber composition. Arm mass and muscle fiber composition were found to correlate statistically significantly with the tremor frequency characteristics. In the further analyses arm mass was found to be the only variable explaining the tremor frequency characteristics; the effects of the muscle structure variables were minor when the effects of arm mass was controlled in partial correlation analyses. Interindividual differences in motor unit firing properties were presumed to explain the dependence found between arm mass and tremor frequency.

Physical activity, VO2max, and jumping height in an urban population.

We studied the interrelations between, on the one hand, the physical activity (frequency, duration, intensity, and mode) measured by a questionnaire and, on the other, VO2max (submaximal bicycle ergometer test) and the explosive muscle strength (vertical jumping height). A random sample of 774 healthy subjects from the city of Turku participated in this study; the subjects were 25, 35, 45, or 55 yr of age. The VO2max of physically active 55-yr-old female subjects was on the same average level as of 25-yr-old females, who were physically inactive. Correspondingly, the average VO2max of physically active 55-yr-old male subjects was above the average level of 25-yr-old males, who were physically inactive. With the exception of the oldest female study group, the jumping test of physically active subjects gave similar results as those of their inactive counterparts who were 10 yr younger. On the basis of the sports events reported by the subjects, we classified the subjects into five activity mode categories. The mode of activity was significantly associated with VO2max in a three-way ANOVA (P = 0.0027) as well as with the jumping test result (P = 0.0001). Mixed training (includes varied types of exercise for the neuromuscular system) was the most beneficial mode of exercise for developing jumping height. The study suggests that the intensity, frequency, and duration of regular physical activity habits during leisure are associated with both VO2max and the jumping height, and that the jumping height results, in particular, are increased by mixed training.

Forearm tremor during three different isometric loadings.

Forearm tremor was studied during a spring (stiffness 1090 N.m-1), a rigid isometric and a "dynamic" isometric (carrying a freely hanging mass) loading at the level of 50% of maximal isometric voluntary contraction. Thirteen physical education students ranging in age between 20 and 28 years flexed their dominant forearm isometrically towards the vertical direction (90 degree elbow angle) against the three different loads on three test occasions seated on a dynamometer which measured the force at the wrist together with vertical tremor (accelerometer). A power spectrum density function was established for the tremor (acceleration) between 1.0 and 19.9 Hz. A bandwidth of 6.9-19.9 Hz was subsequently analyzed in more detail including the determination of peak power (PMAX), peak power frequency (FMAX), mean power frequency (MPF), and average power (PAVER) as well as proposition (%) of the whole spectrum occupied by the selected bandwidth. The FMAX, MPF and band percentage variables had the best reproducibility (Cronbach's Alpha 0.85-0.95), while for the PMAX and PAVER the coefficients were lower but still satisfactory (0.69-0.89). The coefficients were rather similar for all three loading conditions. In the spring loading the spectrum components inside the analyzed frequency band occupied almost 90% of the whole spectrum, FMAX was more clearly distinguished from the rest of the spectrum, and tremor amplitude was higher and tremor frequency lower than in the rigid isometric and "dynamic" loadings. The respective tremor amplitude and frequency characteristics showed statistically significant correlations between the rigid isometric and "dynamic" loading conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Knee angle as a determinant of lower leg tremor.

The effects of knee joint angle (muscle length) and spring load stiffness on some mechanical parameters of lower leg tremor were studied among twelve male subjects during isometric knee extensions against three springs differing in stiffness at knee angles of 90, 110, and 130 degrees. The power spectral density function was estimated for the acceleration (tremor) signal. The results showed knee angular position to have a significant influence on the lower leg tremor parameters so that higher peak frequencies and lower tremor amplitude values were typical for the shorter knee extensor lengths. Frequency changes with knee angle were explained by the effect of changes in stiffness of a spring-mass system (knee extensor musculature) as a function of muscle length. It was suggested that tremor amplitude is influenced by motor unit recruitment and firing characteristics.

Biomechanical effects of fatigue during continuous hurdle jumping.

Jumping drills that include several successive take-offs are popular in many sports events. An understanding of the effects of fatigue on biomechanical parameters during continuous jumping drills is important when selecting drills and their durations for sports training. In the present study, effects of continuous hurdle jumping on myoelectrical (EMG) activity, ground reaction forces, vertical movements of the body's centre of mass and knee joint angle kinematics were studied among eight male volleyball players (age 20-26 years). The subjects jumped hurdles (height 0.65 m) continuously for 45 s with bilateral foot contacts. All of the take-offs were performed from force-platforms which registered the three components of ground reaction force. The two middle take-offs in both directions were used for further analysis. Knee angular data were recorded by an electrical goniometer for determination of angular displacement and velocity. The jumping was videotaped sagittally to determine the location of the centre of mass at different phases of contact and flight, as well as to calculate the movement amplitude for the centre of mass. The EMG activity was monitored using surface electrodes, full-wave rectified and averaged for a pre-contact period of 55 ms as well as for the eccentric and concentric phases of contact for the M. rectus femoris, vastus lateralis and vastus medialis. The ground reaction forces and knee angular data were used to determine the eccentric and concentric phases of contact. The average EMG activity of the knee extensor muscles during the eccentric and concentric phases of contact increased during the jumping drill.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of concentric exercise on serum muscle and collagen markers.

The effect of an acute bout of high-intensity concentric exercise on serum muscle and collagen marker proteins was studied in nine male students. The muscle-derived serum carbonic anhydrase III, myoglobin, and creatine kinase all increased as a result of the exercise. Serum type I procollagen carboxyterminal propeptide decreased at first but started to increase 2 days after the exercise. Serum galactosylhydroxylysyl glucosyltransferase was elevated immediately after the exercise. No significant changes were seen in the concentrations of serum amino-terminal propeptide of type III procollagen or 4-hydroxyproline. It seems that a single bout of heavy concentric exercise causes protein leakage from muscles and probably from the collagen-synthesizing cells of the connective tissue, which may be accompanied by an initial decrease and a subsequent increase in type I collagen production. The activation of type I collagen production seems to depend on the strain and damage of the musculoskeletal system.

Vertical jumping height and horizontal overhead throwing velocity in young male athletes.

The purpose of this study was to examine the effects of calendar and skeletal age, anthropometric dimensions, training history and their interactions on vertical jumping height and horizontal overhead throwing velocity in a cross-section of 318 young male athletes (age range 9-16 years) participating in cross-country skiing (n = 70), basketball (n = 40), apparatus gymnastics (n = 19), ice hockey (n = 50), track and field (n = 89) and wrestling (n = 50). Vertical jumping height was measured with four different loads held on the shoulders and then interpolated for loads representing 0 and 40% body mass. Horizontal overhead throwing velocity using both hands was determined for seven balls of different weights and then interpolated for weights representing 1 and 5% body mass. Both vertical jumping height and overhead throwing velocity were found to increase (P < 0.01) from the skeletally youngest to the oldest cohort when the effects of body height and mass were controlled. The inter-event comparisons did not reveal statistically significant differences in respect of vertical jumping height. Also in the overhead throwing tests, the inter-event differences were small, although the analysis of variance revealed statistically significant (P < 0.001) differences for the skeletal age cohorts of 13 and 14 years. While the quantity of training had no effect on vertical jumping height, it explained the results in the overhead throwing test. The effects of training on vertical jumping and horizontal overhead throwing among adolescent athletes were considered to be small, while maturational processes and anthropometric development followed by increase in calendar age were deemed to be of greater importance.

Determinants of isometric muscle strength in men of different ages.

Values of maximal isometric strength of five muscle groups and associated factors including occupational status, life style and health were studied in three groups of men aged from 31 to 35, 51 to 55, and 71 to 75 years. The results indicated significant differences between the age groups in isometric handgrip, elbow flexion, knee extension, trunk extension and trunk flexion strength. In the youngest group, the manual workers tended to have higher strength values in all muscle groups than the lower and higher status white collar workers, whereas among the middle-aged and oldest men the manual workers tended to have the poorest performance. Good self-rated health and the intensity of physical exercise during leisure were positively associated with muscle strength in the youngest and middle-aged groups whereas in the oldest group the most important variable was home gymnastics. The multivariate structural equation models of isometric strength differed somewhat among the age groups and in these models the above-mentioned variables accounted for from 33% to 43% of the variance in isometric strength within the age groups. The results illustrated the most important factors associated with isometric strength in samples of men of different ages and also provided suggestions as to how these determinants might influence comparisons between different age groups in respect of muscle strength.

Strength characteristics of a healthy urban adult population.

A random sample of 778 subjects representing ages 25, 35, 45 and 55 years were studied for the amount of habitual physical activity, their anthropometric structure, vertical jumping height, trunk extension and flexion torques and dynamic endurance fitness of trunk extension and flexion. The proportion of subjects who were habitually physically active did not change systematically with age. The highest number of physically inactive subjects was found in men and women in the 35-year age group. The results in all the tests used to assess the strength characteristics were statistically significant when related to sex (P less than 0.001) and in all, except the relative maximal isometric torque of trunk extension, when related to age (P less than 0.001). Everyday physical activity was related to the variation in vertical jumping height (P less than 0.001), as well to the dynamic endurance fitness (P less than 0.001) of trunk extension and flexion. The decline in vertical jumping height and dynamic endurance fitness of trunk extension and flexion fitness was found to start at earlier ages than that of relative maximal isometric trunk extension and flexion torques. Dynamic endurance fitness of trunk flexion showed a more pronounced decline with age than trunk extension fitness.

Mechanical work and efficiency in ergometer bicycling at aerobic and anaerobic thresholds.

Internal and external mechanical work, energy consumption and mechanical efficiency were studied in constant-load ergometer bicycling at five different power outputs below, equal to, and above the aerobic (AerT) and anaerobic (AnT) thresholds. The gross, net and true efficiencies of the whole body in five male subjects were calculated. The work against the external load was defined as the external mechanical work. The internal mechanical work was calculated as the sum of the increments of kinetic and potential energy in all body segments by using methods of film analysis. Total energy consumption was measured by combining aerobic and anaerobic energy production. When the power output of the bicycle ergometer was increased from 146 +/- 15 to 283 +/- 17 W, oxygen consumption increased from 2.20 +/- 0.98 to 4.22 +/- 0.20 l min-1 (P less than 0.001), while the oxygen consumption at rest was 0.30 +/- 0.03 l min-1. The concentration of blood lactate increased from 2.2 +/- 0.4 at the lowest work load to 8.6 +/- 1.2 mmol l-1 at the highest work load (P less than 0.001). The amount of external work done per revolution increased from 139 +/- 20 to 277 +/- 29 J (P less than 0.001), while the amount of internal work per revolution remained almost constant (56 +/- 12 J). The gross efficiency in the present study was 17-20%, net efficiency 18-22% and true efficiency 21-30%, respectively. The highest gross and net efficiencies were reached at the AerT. The lowest efficiencies were obtained at highest work load.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanical jumping power in young athletes.

Mechanical jumping power was determined for 286 young male athletes representing six sports events and ranging in calendar and skeletal ages from 8.8 to 17.1 and from 7.8 to 18.1 years, respectively. The subjects performed successive maximal vertical jumps on a contact mat for 30 s. The number of jumps and their cumulative flight time after 15 and 30 s were used for calculations of mechanical power. The jumping performances of the young athletes were found to be reproducible from the age of 10-12 years in respect to the angular displacement of the knee and duration of contact. Absolute mechanical power, as well as power related to body weight, increased with calendar and skeletal ages. Of the anthropometric characteristics, the circumference of the thigh and body weight showed the highest correlation with mechanical power; subjects with the greatest thigh circumference and body weight having the lowest mechanical power. The subjects were divided into 'power' (track and field, gymnastics) and 'endurance' (skiing, orienteering) groups. The former reached higher mechanical power values than the latter. Mechanical power for the second 15-s jumping period was on average 4.7% lower than for the first. The events did not differ from each other in respect of the decrease in power.