Biomedical subjects

A Mero

Publications and source records attributed to A Mero.

At least 19 recordsLinked to original sources

PubMed2005

Protein metabolism and strength performance after bovine colostrum supplementation.

This study was designed to determine the responses of muscle protein, serum amino acids, and strength performance to bovine colostrum supplementation in physically active men. The rest (R) group (n = 6) and the exercise (E) group (n = 6) carried out twice a 2-week experiment randomly assigned in a double-blind fashion with either placebo (PLA; consuming daily 20 g maltodextrin) or bovine colostrum (COL; consuming daily 20 g colostrum supplement) treatment with one month between. On the test day after the treatment period the measurements were carried out in fasting conditions and E carried out a strength training session (STS). The methods involved the infusion of ring-(2)H(5)-phenylalanine, femoral arterial and venous blood sampling, and biopsies from the vastus lateralis muscle. Serum concentration of essential amino acids during recovery was greater (p < 0.05) in the COL groups compared with the PLA groups. Both muscle protein synthesis and breakdown increased (p < 0.05) with COL. There were no differences in phenylalanine net balance or strength performance between the PLA and COL groups. It was concluded that a 2-week supplementation with bovine colostrum in physically active men increases serum concentration of essential amino acids but has no effect either on strength performance or protein net balance in fasting conditions during recovery after STS.

Adult↗

PubMed2002

Serum amino acid responses to three different exercise sessions in male power athletes.

BACKGROUND: The purpose of this study was to investigate serum amino acid responses to 3 different exercise sessions in male power athletes (sprinters and jumpers; n=11). METHODS: All subjects performed 2 running exercise sessions: a short run session (SRS) of 3 x 4 x 60 m with recoveries of 120 and 360 sec, and a long run session (LRS) of 20 sec runs with recoveries of 100 sec until exhaustion. Ten subjects performed a strength exercise session (SES) of 90 min. Serum amino acids (n=21) were assayed 10 min before and 10 min after the sessions. Peak blood lactate was analyzed from fingertip blood samples taken 1 and 5 min after the sessions. RESULTS: The before-after comparisons showed that the essential amino acids (EAAs) decreased by 8.7% (p<0.01) and alanine increased by 26.7% (p<0.001) after SRS. Following LRS the EAAs decreased also by 8.7% (p<0.01) and alanine increased by 25.3% (p<0.001). In the sum of all amino acids there were no changes after SRS and LRS but a significant decrease (14.8%; p<0.01) was observed after SES. Also the EAAs decreased (20.6%; p<0.001) but alanine, taurine and citrulline were the only single amino acids with no changes after SES. The peak blood lactate concentrations after SRS, LRS and SES were 13.8+/-1.9, 16.4+/-1.3 and 2.5+/-0.4 mmol/L, respectively. The lactate value after SES differed (p<0.001) from the values observed after SRS and LRS. The comparison of the changes in the serum amino acid concentrations following the 3 exercise sessions revealed that SRS and LRS were very similar but SES differed from SRS and LRS strongly (p<0.01) in the sum of all amino acids. CONCLUSIONS: The current data indicate that the sum concentrations of all amino acids in serum decrease after the strength exercise session but not after the lactic anaerobic running exercises.

Adult↗

PubMed2001

[Recurrent inguinal hernia after mesh hernioplasty. An emerging problem?].

BACKGROUND: In spite of the successful results of tension free hernioplasties, recurrent inguinal hernias are not an uncommon finding in the clinical practice. METHODS: The authors report their experience in 24 patients observed from January 1994 to December 2000 (23 men, 1 women, min. age 28 yrs, max 78 yrs, mean 58 yrs) who had recurrent inguinal hernia after a tension free hernioplasty. In 22 patients a tension free hernioplasty (Lichtenstein technique 5 patients, Trabucco 7 patients, unclassifiable 10 patients) through an anterior approach was performed while in two, respectively, a Stoppa procedure and a laparoscopic hernioplasty were the first operations; mean recurrence time was 17 months. RESULTS: Mesh and/or plug dislocation was the most frequent cause of recurrence (15 patients), followed by a failure of the internal ring reconstruction (6 patients) and loss of the pubic stitch (2 patients); in 1 patient the mesh was of reabsorbable type. CONCLUSIONS: Mesh hernioplasties represent a valuable progress in inguinal hernia therapy, but increasing clinical experience shows that, together with the experience of the surgeon in the surgical technique, suture of a wide mesh to the surrounding tissues and a adequate inguinal ring reconstruction are critical condition for good results.

Adult↗

PubMed1999

Leucine supplementation and intensive training.

Leucine, isoleucine and valine, the branched-chain amino acids (BCAA), make up about one-third of muscle protein. Of these, leucine has been the most thoroughly investigated because its oxidation rate is higher than that of isoleucine or valine. Leucine also stimulates protein synthesis in muscle and is closely associated with the release of gluconeogenic precursors, such as alanine, from muscle. Significant decreases in plasma or serum levels of leucine occur following aerobic (11 to 33%), anaerobic lactic (5 to 8%) and strength exercise (30%) sessions. In skeletal muscle, there is a decrease in leucine level and a reduction in glycogen stores during exhaustive aerobic exercise. Basal fasting serum leucine levels decrease by 20% during 5 weeks of speed and strength training in power-trained athletes on a daily protein intake of 1.26 g/kg bodyweight. The leucine content of protein is assumed to vary between 5 and 10%. There are suggestions that the current recommended dietary intake of leucine be increased from 14 mg/kg bodyweight/day to a minimum of 45 mg/kg bodyweight/day for sedentary individuals, and more for those participating in intensive training in order to optimise rates of whole body protein synthesis. Consumption of BCAA (30 to 35% leucine) before or during endurance exercise may prevent or decrease the net rate of protein degradation, may improve both mental and physical performance and may have a sparing effect on muscle glycogen degradation and depletion of muscle glycogen stores. However, leucine supplementation (200 mg/kg bodyweight) 50 minutes before anaerobic running exercise had no effect on performance. During 5 weeks of strength and speed training, leucine supplementation of 50 mg/kg bodyweight/day, supplementary to a daily protein intake of 1.26 g/kg bodyweight/day, appeared to prevent the decrease in the serum leucine levels in power-trained athletes. According to 1 study, dietary supplementation of the leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) 3 g/day to humans undertaking intensive resistance training exercise resulted in an increased deposition of fat-free mass and an accompanying increase in strength. Muscle proteolysis was also decreased with HMB, accompanied by lower plasma levels of enzymes indicating muscle damage and an average 50% decrease in plasma essential amino acid levels. Furthermore, BCAA supplementation (76% leucine) in combination with moderate energy restriction has been shown to induce significant and preferential losses of visceral adipose tissue and to allow maintenance of a high level of performance. Caution must be paid when interpreting the limited number of studies in this area since, in many studies, leucine has been supplemented as part of a mixture of BCAA. Consequently, further research into the effects of leucine supplementation alone is needed.

Dietary Supplements↗

PubMed1998

Plasma catecholamine and serum testosterone responses to four units of resistance exercise in young and adult male athletes.

The plasma noradrenaline (NA) and adrenaline (A) concentration responses of seven young male athletes [15 (SD 1) years] and seven adult male athletes [25 (SD 6) years] were investigated together with the serum testosterone (Tes) concentration responses in four different half-squatting exercises. The loads, number of repetitions, exercise intensity and recovery between the sets were manipulated such that different types of metabolic demand could be expected. However, the amount of work done was kept equal in each kind of exercise. After the most exhausting unit of exercise (E3; two sets of 30 repetitions with 50% of 1 repetition maximum and with 2-min recovery between the sets) the plasma NA concentration was significantly lower in the younger than in the adult subjects [15.7 (SD 7.8) vs 32.7 (SD 13.2) nmol x l(-1), P < 0.05], while the A concentrations were similar. In the other three exercises no differences in the plasma catecholamine concentration responses among the groups were observed. The postexercise Tes concentrations, however, were significantly lower in the younger than in the adult subjects in every exercise unit. No correlations between the plasma catecholamine and serum Tes concentration responses were observed in any of the exercise units in either group. The results of the present study may suggest reduced sympathetic nervous activity in the younger subjects compared to the adults in response to exhausting resistance exercise. The results may also suggest that the catecholamines were less involved in eliciting an increase in Tes secretion in these resistance exercises.

Adolescent↗

PubMed1997

Effects of bovine colostrum supplementation on serum IGF-I, IgG, hormone, and saliva IgA during training.

The purpose of this study was to examine the effects of bovine colostrum supplementation (Bioenervi) on serum insulin-like growth factor I (IGF-I), immunoglobulin G, hormone, and amino acid and saliva immunoglobulin A concentrations during a strength and speed training period. Nine male sprinters and jumpers underwent three randomized experimental training treatments of 8 days separated by 13 days. The only difference in the treatments was the drink of 125 ml consumed per day. Posttraining increases were noticed for serum IGF-I in the 25-ml Bioenervi treatment (125 ml contained 25 ml Bioenervi) and especially in the 125-ml Bioenervi treatment (125 ml contained 125 ml Bioenervi) compared with the placebo (normal milk whey) treatment (P < 0.05). The change in IGF-I concentration during the 8-day periods correlated positively with the change in insulin concentration during the same periods with 25-ml Bioenervi treatment (r = 0.68; P = 0.045) and with 125-ml Bioenervi treatment (r = 0.69; P = 0.038). Serum immunoglobulin G, hormone, and amino acid and saliva immunoglobulin A responses were similar during the three treatments. It appears that a bovine colostrum supplement (Bioenervi) may increase serum IGF-I concentration in athletes during strength and speed training.

Adult↗

PubMed1997

Leucine supplementation and serum amino acids, testosterone, cortisol and growth hormone in male power athletes during training.

OBJECTIVE: The purpose of the present study was to examine the effects of leucine supplementation on the amino acid and hormone profile during training. EXPERIMENTAL DESIGN: The study was a randomised double-blind cross-over study during 10 weeks of training. SETTING: The study occurred during a sport training period. PARTICIPANTS: Twenty adult male track and field power athletes finished the study. INTERVENTIONS: The subjects were given leucine (50.0 +/- 3.3 mg/ kg body weight per day) or placebo tablets. MEASUREMENTS: The measurements were carried out before, in the middle of, and after 10 weeks. RESULTS: The serum leucine concentration decreased significantly (p < 0.05) in the placebo group, by 20.1% (from 189 +/- 45 to 151 +/- 21 mumol/l) during the first 5 weeks, but not during the second 5 weeks (180 +/- 61 vs 154 +/- 23 mumol/l). When leucine was taken there were no changes in the serum leucine concentration. The total serum amino acid pool decreased significantly (p < 0.01) in all subjects, by 21.2% during the 10-week training period. The decrease occurred mostly during the first 5 weeks. Glutamine decreased (37.1%; p < 0.01) most of the single amino acids. The serum testosterone concentration increased by 20.7% (p < 0.05) and the serum cortisol concentration by 8.0% (p < 0.05) in all subjects during the first 5 weeks. During the second 5 weeks the testosterone concentration decreased by 19.0% (p < 0.001). CONCLUSIONS: The present findings indicate that on a daily protein intake of 1.26 g/kg body weight the serum concentrations of amino acids are lowered considerably and earlier than the decrease in the serum testosterone concentration during the training season in adult male power athletes. The leucine supplementation of 50 mg/kg body weight per day appears to prevent the decrease in the serum leucine concentration during intensive training.

Adult↗

PubMed1996

Important determinants of anaerobic running performance in male athletes and non-athletes.

The purpose of this study was to investigate the importance of selected metabolic and neuromuscular determinants as predictors of anaerobic running performance. The subjects were male 400-m runners (n = 21), middle- (n = 8) and long-distance runners (n = 11), power athletes (n = 14) and physically active men (n = 34). Maximal power (Pmax), peak blood lactate concentration (peak BLa), power at 10 mM blood lactate level (P10mM), height (CMJrest) and percentage decrease (CMJdecrease) of the counter-movement jump were determined by the maximal anaerobic running test (MART). In addition, maximal oxygen uptake (VO2max) was determined on a treadmill and maximal running velocity (V30m) was measured by the 30-m speed test on a track. Stepwise regression analysis revealed that V30m, P10mM and peak BLa accounted for 92% (P < 0.001) of the variation in Pmax. Regression analysis showed also that V30m, P10mM and delta P (the difference between Pmax and VO2max) were the most important determinants of the 400-m run on a track within a homogeneous group of 400-m runners. The middle-distance and 400-m runners had higher Pmax and P10mM than the long-distance and control group (p < 0.05). The 400-m runners had superior V30m and delta P than the other groups. Furthermore, the 400-m runners and power athletes had higher peak BLa than the long-distance and control group (p < 0.05). The present findings showed that V30m, P10mM and peak BLa determined by the 30-m speed test and the MART were the most important components of anaerobic work capacity. These determinants could be used to explain the differences in anaerobic work capacity between various sport groups as well as between different athletes.

Adult↗

PubMed1996

Effects of sprint training on anaerobic performance characteristics determined by the MART.

The purpose of this study was to investigate the effects of sprint training on the anaerobic performance characteristics in well-trained sprint runners employing the maximal anaerobic running test (MART). Another purpose was to study the applicability of MART in the prescription of sprint training. Nine male sprint runners performed the MART before and after a 10-week intensive training period. The MART consisted of n.20-s runs on a treadmill with a 100-s recovery between the runs. Initial power, expressed as O2 demand (74 ml.kg-1.min-1), was increased by 6 ml.kg-1.min-1 for each consecutive run until exhaustion. Blood lactate concentration was measured at rest and after each run. Maximal power (Pmax), power at 10 mM (P10mM) and 3 mM (P3mM) blood lactate levels, and peak blood lactate concentration (peak BLa) were determined from the blood lactate vs O2 demand curve. The Pmax increased from 118.6 +/- 6.0 to 122.6 +/- 4.9 ml kg-1.min-1 (P = 0.009) during the training period and the changes of Pmax correlated positively with the volume of bounding exercises (r = 0.64; p = 0.032). The volume of extensive interval training correlated positively with the changes of P3mM (r = 0.62; p = 0.040) and negatively with the changes of P[10mM-3mM] (r = -0.68; p = 0.016) and peak BLa (r = -0.69; p = 0.019) during the particular training period. A positive correlation was also found between the changes of CMJrest and the volume of bounding and strength training (r = 0.60; p = 0.044). The present results suggested that sprint training induces an adaptive increase in the maximal anaerobic running power in well-trained male sprint runners. Furthermore, correlation analysis revealed that individual changes in P3mM, peak BLa, Pmax and CMJrest were related to the volume of specific training methods. Therefore we could conclude that the results of the MART could provide guidance in prescribing training for sprint running.

Adult↗

PubMed1996

Comparison of two maximal anaerobic cycling tests.

The purpose of this study was to compare two cycle ergometer modifications of the maximal anaerobic running test (MART) with each other and with the MART. Ten male physical education students performed the two maximal anaerobic cycling tests (MACT) in a random order and the MART between the MACTs. Each test consisted of n.20-s exercise bouts with a 100-s recovery period between them. Based on the ACSM equations the oxygen demand of the initial bout in each test equalled 56 ml.kg-1.min-1 and the increase for each consecutive bout was 6 ml.kg-1.min-1. In MACTres the resistance was increased and the pedalling frequency was kept constant (100 rpm) while in MACTfreq the frequency was increased and the resistance was constant (0.077 x body weight). In the MART the velocity of the treadmill was increased and the slope was constant (4 degrees). Blood lactate (BLa) concentration was measured at rest, 40 s after each run and during a 10-min recovery period. Maximal power (Pmax) was similar in the MART, MACTres and MACTfreq (107 +/- 4, 107 +/- 8 and 105 +/- 6 ml.kg-1.min-1, respectively) while significant differences (p < 0.05) were observed in the peak BLa (12.8 +/- 1.3, 15.6 +/- 1.7, and 14.7 +/- 2.1 mM, respectively). BLa was lower in the MACTfreq than in the MACTres until the oxygen demand of 86 ml.kg-1.min-1 and it was higher in both MACTs compared to the MART at each workload. We concluded that the MART can be modified for the bicycle ergometer although metabolic acidosis was greater in bicycle modifications. Further, the comparison of the MACTres and MACTfreq showed that blood lactate accumulation was greater at the higher pedalling frequency.

Acidosis↗

PubMed1995

Blood lactate and ammonia in short-term anaerobic work following induced alkalosis.

This study was designed to investigate the effect of an induced metabolic alkalosis on a 300 m sprinting time in six elite 400 m runners. The subjects competed as pairs, on two separate occasions, in a standard racing format, three hours after ingestion of either an alkaline (sodium citrate, 0.5 g.kg-1 body weight) or a placebo solution (calcium carbonate, 0.5 g.kg-1 body weight). The results showed that following alkaline ingestion mean sprinting time was not improved. Peak blood lactate during recovery was higher after sodium citrate administration than after placebo (19.88 +/- 2.09 vs 18.82 +/- 1.84 mmol.l-1, p < 0.01). No difference was observed in peak blood ammonia between the alkaline and placebo treatments (187.0 +/- 37.0 vs 188.8 +/- 49.0 mumol.l-1). The absence of effects on performance confirms that when exercise of short duration (30 to 40 s) is used, alkaline agents have minor or no effects on performance. The altered relationship observed between blood lactate and ammonia under placebo and buffering loading conditions suggests that the regulation of lactate and ammonia metabolism is unrelated.

Adult↗

PubMed1994

EMG activities and ground reaction forces during fatigued and nonfatigued sprinting.

The present study was designed to investigate EMG activities and ground reaction forces during fatigued and nonfatigued running. Ten male sprint runners volunteered to run a maximal 20-m speed test, a 400-m time trial, and submaximal 20-m runs at the average speed of the first 100 m of the 400 m. During the latter stage of each run, ground reaction forces and EMG activity of four leg muscles were recorded. EMG activities were time averaged during three phases of running: preactivation, braking, and propulsion phase. The resultant ground reaction forces both in the braking (P < 0.001) and in the propulsion phase (P < 0.01) were greater in the maximal and submaximal 20 m than at the end of the 400 m. The averaged EMG during the braking phase (P < 0.01) and during the total ground phase (P < 0.05) was smaller in the submaximal 20 m than at the end of the 400 m. On the other hand the averaged EMG was greater during the maximal 20 m than at the end of the 400 m during the propulsion phase (P < 0.001) and during the total ground phase (P < 0.05). In addition, the more the preactivity increased the less the resultant ground reaction force decreased in the braking phase during the 400 m run (r = 0.77, P < 0.05). It was concluded that the role of the increased neural activation was to compensate for muscular fatigue and the preactivation had an important role in maintaining force production during the 400-m run. In addition, the fatigue was different in each working muscle.

Adult↗

PubMed1993

A new method for the evaluation of anaerobic running power in athletes.

A new maximal anaerobic running power (MARP) test was developed. It consisted of n.20-s runs on a treadmill with a 100-s recovery between the runs. During the first run the treadmill speed was 3.97 m.s-1 and the gradient 5 degrees. The speed of the treadmill was increased by 0.35 m.s-1 for each consecutive run until exhaustion. The height of counter-movement jumps and blood lactate concentration ([la-]b) were measured after each run. Submaximal ([la-]b = 3 mmol.l-1 and 10 mmol.l-1) and maximal speed and power (W3mmol, W10mmol and Wmax, respectively) were calculated and W was expressed in oxygen equivalents according to the American College of Sports Medicine equation. Thirteen male athletes whose times over 400 m ranged from 47.98 s to 54.70 s served as subjects. In the MARP-test the speed at exhaustion was 6.89 (SD 0.28) m.s-1 corresponding to a Wmax of 118 (SD 5) ml.kg-1 x min-1. The peak [la-]b after exhaustion was 17.0 (SD 1.6) mmol.l-1. A significant correlation (r = 0.89, P < 0.001) was observed between the Wmax and the average speed in the 400-m sprint. The maximal 20-m sprinting speed on a track and W10mmol correlated with both the Wmax and the 400-m speed. It was concluded that the new method allows the evaluation of several determinants of maximal anaerobic performance including changes in the force-generating capacity of leg muscles and [la-]b relative to the speed of the sprint running. the [la-]b at submaximal sprinting speed was suggested as describing the anaerobic sprinting economy.

Adult↗

PubMed1993

Aerobic characteristics, oxygen debt and blood lactate in speed endurance athletes during training.

Aerobic characteristics, oxygen debt and blood lactate were analysed in 20 male speed endurance athletes (400 m sprinters and 400 m hurdlers). The subjects were tested three times; at the beginning of March, at the end of May and at the end of August. Aerobic and anaerobic threshold and maximal oxygen uptake measured on the treadmill decreased (p < 0.05-0.01) from the second test occasion to the third one. The anaerobic work test on the treadmill was a constant load test at 5.56 m.s-1 with a slope of 4 degrees. The time to exhaustion increased (p < 0.05) from the first test occasion (112 +/- 17 s) to the second one (136 +/- 35 s) and did not change in the last test (135 +/- 25 s). Following the anaerobic work test oxygen debt was measured during 20 minutes. The highest total oxygen debt values (144 +/- 19 ml.kg-1) were observed in the second test occasion. Peak blood lactate following the anaerobic work increased (p < 0.05) from the first test occasion to the second one and remained at the same level during the next three competitive months. The good speed endurance athletes differed from the poor counterparts in time to exhaustion (p < 0.01), in 100 m record time (p < 0.01) and in maximal oxygen uptake (p < 0.05). Our results suggest that aerobic characteristics decrease during the competitive period in speed endurance athletes. The anaerobic performance capacity including work time and peak blood lactate is at high level in the competitive period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Biomechanics of sprint running. A review.

Understanding of biomechanical factors in sprint running is useful because of their critical value to performance. Some variables measured in distance running are also important in sprint running. Significant factors include: reaction time, technique, electromyographic (EMG) activity, force production, neural factors and muscle structure. Although various methodologies have been used, results are clear and conclusions can be made. The reaction time of good athletes is short, but it does not correlate with performance levels. Sprint technique has been well analysed during acceleration, constant velocity and deceleration of the velocity curve. At the beginning of the sprint run, it is important to produce great force/power and generate high velocity in the block and acceleration phases. During the constant-speed phase, the events immediately before and during the braking phase are important in increasing explosive force/power and efficiency of movement in the propulsion phase. There are no research results available regarding force production in the sprint-deceleration phase. The EMG activity pattern of the main sprint muscles is described in the literature, but there is a need for research with highly skilled sprinters to better understand the simultaneous operation of many muscles. Skeletal muscle fibre characteristics are related to the selection of talent and the training-induced effects in sprint running. Efficient sprint running requires an optimal combination between the examined biomechanical variables and external factors such as footwear, ground and air resistance. Further research work is needed especially in the area of nervous system, muscles and force and power production during sprint running. Combining these with the measurements of sprinting economy and efficiency more knowledge can be achieved in the near future.

Acceleration↗

PubMed1991

Relationships between muscle fibre characteristics and physical performance capacity in trained athletic boys.

The relationships between muscle fibre characteristics and the physical performance capacity of trained athletic boys (aged 11-13 years) were studied over 2 days. The subjects were divided into two groups according to muscle fibre distribution. The 'fast' group (FG) comprised 10 subjects (sprinters, weightlifters, tennis players) with more than 50% fast-twitch fibres (type II), and the 'slow' group (SG) comprised 8 subjects (endurance runners, tennis players, one weightlifter) with more than 50% slow-twitch fibres (type I) in their vastus lateralis muscle. The 'fast' group had 59.2 +/- 6.3% and the 'slow' group had 39.4 +/- 9.8% type II fibres. Other clear differences (P less than 0.05-0.01) between the groups were observed as regards reaction time, rate of force development and rise of the body's centre of gravity in the squatting jump. For these variables, the 'fast' group was superior to the 'slow' group. Muscle fibre distribution (% type II) correlated (P less than 0.05-0.01) negatively with reaction time. Muscle fibre area (% type II) correlated negatively with reaction time (P less than 0.05-0.001) and positively with chronological age (P less than 0.05) height (P less than 0.05), mass (P less than 0.001), serum testosterone (P less than 0.05), force production (P less than 0.05-0.01) and blood lactate (P less than 0.05) in the 60-s maximal anaerobic test. There were no significant correlations between muscle fibre characteristics and maximal oxygen uptake. The present study assumes that heredity partly affects the selection of sporting event. Growth, development and training are associated with muscle fibre area, which affects the physical performance capacity of the neuromuscular system in trained young boys.

Adipose Tissue↗

PubMed1990

Reaction time and electromyographic activity during a sprint start.

Eight male sprinters were filmed running three maximal starts over 3 m on a long force platform. The subjects were divided into two groups (n = 4) according to the leg on which the electromyograph (EMG) electrodes were fixed. When in the set position one group had electrodes on the front leg (FLG) and the other group on the rear leg (RLG). The EMG activities of the gastrocnemius caput laterale muscle (GA), vastus lateralis muscle (VL), biceps femoris caput longum muscle (BF), rectus femoris muscle (RF) and gluteus maximus muscle (GM) were recorded telemetrically using surface electrodes. Total reaction time (TRT) was defined as the time from the gun signal until a horizontal force was produced with a value 10% above the base line. Pre-motor time was defined as the time from the gun signal until the onset of EMG activity and motor time (MT) as the time between the onset of EMG activity and that of force production. Reproducibility of the reaction time variables was satisfactory (r = 0.79-0.89; coefficient of variation = 8.8%-11.6%). The TRT was 0.121 s, SD 0.014 in FLG and 0.119 s, SD 0.011 in RLG. The MT ranged from 0.008 s, SD 0.009 (GM) to 0.057 s, SD 0.050 (GA) in FLG and from 0.018 s, SD 0.029 (GA) to 0.045 s, SD 0.009 (GM) in RLG. In some individual cases there were no MT values before horizontal force production.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

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

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 less than 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 less than 0.001), speed-strength (P less than 0.01-P less than 0.001) and anaerobic capacity (P less than 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 = 0.49-0.58; P less than 0.05-P less than 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 less than 0.01-P less than 0.001) and anaerobic capacity (r = 0.49; P less than 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.

Anaerobiosis↗