Biomedical subjects

A Mero

Publications and source records attributed to A Mero.

25 records · Page 2Linked to original sources

PubMed1990

Physiological performance capacity in different prepubescent athletic groups.

Endurance, strength and speed capacity were investigated among prepubescent male weight lifters (EL), endurance runners (ER) and sprint runners (SR). The subjects were selected by their coaches and all of them were classified as promising and successful junior athletes in the age groups of 10-13 years. Twelve boys belonged to athletic group (AG) and their performance capacity was compared to normally active control (C) boys (n = 9). Biological age was significantly (p less than 0.05) greater in AG (11.3 +/- 0.9 years) than in C (10.2 +/- 1.4 years) but in chronological age there was no difference between the groups. Maximal oxygen uptake was significantly (p less than 0.05) higher in AG (62.3 +/- 3.1 ml.kg-1.min-1) than in C (55.4 +/- 7.7 ml.kg-1.min-1). The endurance runners had the highest value (66.5 +/- 2.9 ml.kg-1.min-1). In anaerobic characteristics there were no significant differences. The rise of centre of gravity (0.26 +/- 0.03 m) of AG in a test for the best drop jump was clearly (p less than 0.05) higher than that (0.22 +/- 0.03 m) of C. The weight lifters and sprint runners were the best in the test for force production. AG had significantly (p less than 0.01) shorter choice reaction time (261 +/- 39 ms) than C (344 +/- 81 ms). Testosterone correlated with jump performances (p less than 0.05), biological age (p less than 0.01) and chronological age (p less than 0.001). Growth hormone correlated significantly only with biological age (p less than 0.05) and testosterone (p less than 0.001). In conclusion, endurance capacity (aerobic) and strength capacity were greater in the athletic group than in the control group and it was suggested that training background and more advanced biological maturation of the athletes affected especially their strength capacity. The parameters used in this investigation can be utilized for talent selection in sport.

Adolescent↗

PubMed1989

Neuromuscular, metabolic and hormonal profiles of young tennis players and untrained boys.

This study compared the neuromuscular, metabolic and hormonal profiles of trained prepubescent tennis players and an untrained group. The boys in the experimental group (n = 9; mean age +/- S.D. = 11.4 +/- 0.5 years) had participated in tennis training for 2.3 +/- 1.0 years and the boys in the control group (n = 9; mean age +/- S.D. = 10.9 +/- 0.4 years) were normal active volunteers. The tennis players were found to be physically more active than the controls when the comparison was made for either 1 year (4.9 +/- 1.8 vs 2.6 +/- 2.5 times per week; P less than 0.05) or for 1 week (3.4 +/- 1.2 vs 0.4 +/- 0.5 times; P less than 0.001) preceding the tests. Choice reaction time was significantly (P less than 0.01) shorter in the experimental group (258 +/- 16 ms) than in the control group (344 +/- 81 ms). Dropping height in the best drop jump was significantly (P less than 0.05) higher in the tennis players (0.46 +/- 0.19 m) than in the control boys (0.27 +/- 0.10 m). The tennis players had significantly lower oxygen consumption at the 'anaerobic threshold' than the controls (P less than 0.05). There were no significant differences between the groups in serum hormone levels. The small differences that existed may have been caused by active participation in sport by the tennis players.

Anaerobic Threshold↗

PubMed1989

Specificity of endurance, sprint and strength training on physical performance capacity in young athletes.

Three prebubescent athlete groups of endurance runners (E; n = 4), sprinters (S; n = 4) and weightlifters (WL; n = 4) and one control group (C; n = 6) as well as one junior but postpubescent weightlifter group (JWL; n = 6) volunteered as subjects in order to investigate specific effects of endurance, sprint and strength training on physical performance capacity during a 1 year follow-up period. The prepubescent E-group had higher (p less than 0.05) VO2 max (66.5 +/- 2.9 ml x kg1 x min-1) already at the beginning of the study than the other three groups. The prepubescent WL-group demonstrated greater (p less than 0.05) maximal muscular strength than the E-group and the WL-group increased its strength greatly by 21.4% (p less than 0.05) during the follow-up. No significant differences were observed in physical performance capacity between the prepubescent WL- and S-groups. Both groups demonstrated a slightly (ns.) better force-time curve recorded from the leg extensor muscles than the E-group and significant (p less than 0.05) increases occurred in these two groups in dynamic explosive performance during the follow-up. The postpubescent JWL-group demonstrated much greater (p less than 0.001) muscular mass and maximal strength than the prepubescent groups. No significant changes occurred in explosive types of performances in these athletes but significant (p less than 0.05) increase took place in the maximal neural activation and strength of the leg extensor muscles during the 1 year.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1988

Blood lactate production and recovery from anaerobic exercise in trained and untrained boys.

Blood lactate production and recovery from anaerobic exercise were investigated in 19 trained (AG) and 6 untrained (CG) prepubescent boys. The exercises comprised 3 maximal test performances; 2 bicycle ergometer tests of different durations (15 s and 60 s), and running on a treadmill for 23.20 +/- 2.61 min to measure maximal oxygen uptake. Blood samples were taken from the fingertip to determine lactate concentrations and from the antecubital vein to determine serum testosterone. Muscle biopsies were obtained from vastus lateralis. Recovery was passive (seated) following the 60 s test but that following the treadmill run was initially active (10 min), and then passive. Peak blood lactate was highest following the 60 s test (AG, 13.1 +/- 2.6 mmol.1-1 and CG, 12.8 +/- 2.3 mmol.1-1). Following the 15 s test and the treadmill run, peak lactate values were 68.7 and 60.6% of the 60 s value respectively. Blood lactate production was greater (p less than 0.001) during the 15 s test (0.470 +/- 0.128 mmol.1-1.s-1) than during the 60 s test (0.184 +/- 0.042 mmol.1-1.s-1). Although blood lactate production was only nonsignificantly greater in AG, the amount of anaerobic work in the short tests was markedly greater (p less than 0.05-0.01) in AG than CG. Muscle fibre area (type II%) and serum testosterone were positively correlated (p less than 0.05) with blood lactate production in both short tests. Blood lactate elimination was greater (p less than 0.001) at the end of the active recovery phase than in the next (passive) phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobiosis↗

PubMed1987

Neuromuscular and anaerobic performance of sprinters at maximal and supramaximal speed.

Neuromuscular and anaerobic performance was investigated in nine male sprinters who were running at maximal and supramaximal speeds. Supramaximal running was performed by a towing system. A rubber rope pulled by an electronic motor towed the runner, and the angle of draught ranged from 10 degrees to 17 degrees upward from the horizontal. All runs were filmed at 100 frames X s-1, and ground reaction forces were measured with a long force platform system. EMGs were recorded telemetrically with surface electrodes from five leg muscles. Blood lactate and oxygen debt were measured during recovery. The results indicated that in supramaximal running the increases in velocity (4.3%-4.6%) were associated with increase in stride length (P less than 0.01). Comparison of the ground reaction forces showed that in the impact phase maximal force, average force, work, and power were significantly (P less than 0.01-0.001) greater in a horizontal direction and maximal and average forces were greater (P less than 0.05-0.01) in a vertical direction compared with a preceding maximal run. There were no significant differences in EMG activity of any studied muscle between the various runs. Peak blood lactate was 27.7% (P less than 0.001) and oxygen debt 30.3% (P less than 0.01) higher after maximal than supramaximal runs. It is concluded that supramaximal running with towing horizontally and vertically simultaneously causes increases in stride length and changes are associated with a smaller energy expenditure despite the high intensity of the performance.

Adult↗

PubMed1987

Electromyographic activity in sprinting at speeds ranging from sub-maximal to supra-maximal.

Eleven male and eight female sprinters were filmed when running at five different speeds from sub-maximal to supra-maximal levels over a force platform. Supra-maximal running was performed by a towing system. The electromyographic (EMG) activity of 10 muscles was recorded telemetrically using surface electrodes. Pre-activity (PRA), activity during ground contact, immediate post-contact activity, and minimum activity were the major EMG parameters analyzed from two consecutive strides. Reproducibility of the variables used was rather high (r = 0.85 to 0.90 and coefficient of variation = 6.6 to 9.7%). The results demonstrated increases (P less than 0.001) in PRA and forces in the braking phase when running speed increased to supra-maximum. PRA correlated (P less than 0.01) with the average resultant force in the braking phase. Relative PRA (percentage of maximal value during ipsilateral contact) remained fairly constant (about 50 to 70%) at each speed. In the propulsion phase of contact, integrated EMG activity and forces increased (P less than 0.001) to maximal running, but at supra-maximal speed the forces decreased non-significantly. Post-contact activity and minimum activity increased (P less than 0.001) to maximal running but the supra-maximal running was characterized by lowered integrated EMG activities in these phases. Post-contact activity correlated (P less than 0.05) with average resultant force in the propulsion phase of the male subjects when running velocity increased. It was suggested that PRA increases are needed for increasing muscle stiffness to resist great impact forces at the beginning of contact during sprint running.

Adolescent↗

PubMed1986

Force-, EMG-, and elasticity-velocity relationships at submaximal, maximal and supramaximal running speeds in sprinters.

The relationships between ground reaction forces, electromyographic activity (EMG), elasticity and running velocity were investigated at five speeds from submaximal to supramaximal levels in 11 male and 8 female sprinters. Supramaximal running was performed by a towing system. Reaction forces were measured on a force platform. EMGs were recorded telemetrically with surface electrodes from the vastus lateralis and gastrocnemius muscles, and elasticity of the contact leg was evaluated with spring constant values measured by film analysis. Data showed increases in most of the parameters studied with increasing running speed. At supramaximal velocity (10.36 +/- 0.31 m X s-1; 108.4 +/- 3.8%) the relative increase in running velocity correlated significantly (P less than 0.01) with the relative increase in stride rate of all subjects. In male subjects the relative change in stride rate correlated with the relative change of IEMG in the eccentric phase (P less than 0.05) between maximal and supramaximal runs. Running with the towing system caused a decrease in elasticity during the impact phase but this was significant (P less than 0.05) only in the female sprinters. The average net resultant force in the eccentric and concentric phases correlated significantly (P less than 0.05-0.001) with running velocity and stride length in the maximal run. It is concluded that increased neural activation in supramaximal effort positively affects stride rate and that average net resultant force as a specific force indicator is primarily related to stride length and that the values in this indicator may explain the difference in running velocity between men and women.

Adult↗