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.

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.

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.

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.

Some biomechanical aspects of the foot and ankle in athletes with and without shin splints.

Thirteen adult male athletes (long-distance runners and orienteerers without foot problems) and 35 male athletes with shin splints were compared with respect to: 1) the position of the lower leg and the heel while standing, 2) the passive range of mobility in the subtalar joint, and 3) the angular displacement between the calcaneus and the midline of the lower leg (Achilles tendon angle) while running with bare feet on a treadmill. In standing, the two groups differed statistically significantly in the Achilles tendon angle, which values were greater in the shin splint group. With respect to passive mobility, the athletes with shin splints had significantly greater (P less than 0.05-0.01) angular displacement values in inversion, eversion, and in their sum than the control group. While running, the Achilles tendon angle of the shin splint group was significantly greater (P less than 0.01) at the heel strike. Further, the shin splints group had a significantly greater (P less than 0.01) angular displacement between the heel strike and the maximal everted position. The results suggest structural and functional differences in the feet and ankles between healthy athletes and those with shin splints.

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.

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.

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)

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.

Effects of pretension on isometric force production.

This study was designed to investigate the effect of muscle fiber distribution and pretension at various submaximal contraction levels on the isometric force-time curve during knee extension. Thirteen male physical education students volunteered as subjects. They were instructed to react to an auditory and light signal by extending their right knee as quickly and forcefully as possible. The contractions were performed from seven pretension levels ranging from 0% to 70% of maximal voluntary contraction value (MVC). The isometric force-time curves were analyzed for their maximal rate of isometric force production. Preliminary tension was found to have statistically significant, decreasing effects on isometric maximal strength produced from the pretension levels of 20%, 30%, and 40% of MVC and on the rate of isometric force production (RFD). Relatively, the decrease was greater for the RFD than for the maximal strength. The effect of the 20% preliminary tension on the RFD was greater (P less than 0.05) for subjects rich in fast-twitch muscle fibers in their m. vastus lateralis than for subjects rich in slow-twitch fibers. At the other preliminary tension levels, the intergroup differences did not reach the level of statistical significance.

Anthropometric and physical performance characteristics of male volleyball players.

Fourteen Finnish and ten Russian elite male volleyball players were studied for their anthropometric dimensions, maximal isometric trunk extension and flexion, leg extension strength and vertical jumping height. In addition, the height of rise of the body centre of gravity h (C.G.), and the height of the hand and ball were analyzed from a video tape in spike and block jumps taken during actual competition. The two teams were found to differ significantly in the h (C.G.) during a vertical jumping test where a preliminary counter movement was allowed and in the lengths of lower limbs and legs; the Russian volleyball players jumped higher and had longer lower extremities. In actual competition, the hands of the Russian players while performing a spike were on the average ten centimeters higher (p less than .01) than the hand of the Finnish players. No significant differences were found, however, between the teams in the h (C.G.) during spiking. This finding seems to suggest that the Russians have better spike technique.

Changes in motor unit activity and metabolism in human skeletal muscle during and after repeated eccentric and concentric contractions.

This study was designed to investigate electromyographic (EMG), muscle glycogen and blood lactate changes in quadriceps muscle group during repeated 40 maximal eccentric and concentric contractions, and to follow the recovery in EMG, muscle glycogen and serum creatine kinase values during a 4 day period following the work test. The subjects were normal males and test order (eccentric or concentric) was randomly selected. The results indicated first, that the EMG parameters (IEMG, AMUP), muscle glycogen and blood lactate changed in a similar manner during the both fatigue loads. Despite the high tension work no selective depletion of glycogen could be observed in the slow or fast twitch muscle fibres in either type of work. The restoring of muscle glycogen occurred in a similar manner after the both fatigue loads, and no significant differences were present between eccentric and concentric works in the serum creatine kinase levels for a 2 days period. The eccentric work was associated with muscle soreness, which was strongest during the second day after the termination of the work test. The recovery of the EMG parameters were also delayed in eccentric fatigue. After concentric fatigue EMG-activity returned to normal values within 2 days.

Force-time characteristics and fiber composition in human leg extensor muscles.

Recording of the force-time (f-t) characteristics of muscular contraction expresses the rate at which tension is developed. To further understand the problems involved in force production during voluntary contraction, the f-t curve was registered during maximal voluntary isometric extension of both legs performed in the sitting position with the knee angle at 107 degrees. 38 athletes representing various sport events, five pairs of monozygous, and ten pairs of dizygous twins were used as subjects. The reference group consisted of eight normal men. The data disclosed that the time to produce certain force levels showed good trial-to-trial and satisfactory day-to-day reproducibility below tension levels of 0.9 x PO. At these force levels the time of tension development was positively (p less than 0.05) related to the per cent distribution of slow twitch fibers in the vastus lateralis muscle. This result is consistent with animal experiments concerning the mechanical characteristics of slow and fast muscles. In addition, it was observed that the athletic groups had f-t curves different from the other subjects. Genetic factors had only slight influence on the f-t measurement.

Effects of fatigue on isometric force- and relaxation-time characteristics in human muscle.

Effects of intermittent one leg isometric fatigue on maximal isometric force, force production, relaxation and blood lactate were studied using 29 male students as subjects. The relative changes of variables during fatigue and recovery were intercorrelated together with muscle structure variables, which were determined using needle biopsy technique. Maximal force decreased, force production and relaxation became slower and muscle lactate increased during fatigue. Change of maximal force, force production and lactate during fatigue as well as recovery of maximal force and lactate after fatigue were correlated significantly to muscle fiber distribution. Fatiguability of the force-time characteristics was therefore influenced by the differences in the metabolic profiles of the individual muscle fibers. However, ability to relax the muscle quickly was not observed to be dependent on muscle structure. This suggest that different fatigue mechanisms might be present in relaxation than in force production.