Long-term effects of whole-body vibration training in high-level female basketball players

AIM

The aim of this study was to investigate the long-term effects of Whole-Body Vibration (WBV) training on the jumping capabilities of high-level female basketball players.

METHODS

A 12-week WBV program was applied to 10 national and international level female basketball players. They were randomly distributed into a control group (CG: 23.2±3.96 years, 69.64±11.17 kg, 179.7±7.96 cm) and an experimental group (VG: 24.0±2.65 years, 70.17±9.86 kg, 181.9±10.83 cm). In order to determine the effects of the WBV program on the jumping capabilities of the subjects, the following tests were used: SJ, CMJ, ACMVJ, and 15-seconds maximal jump.

RESULTS

In the SJ test, the CG significantly increased from 455.4±25.91 to 476.6±26.6 ms (+4.42%; P=0.05), while the VG also increased significantly from 455±15.62 to 478.33±16.56 ms (+5.13%; P=0.02). In the CMJ test, the CG significantly increased from 470.2±12.15 to 496±23.38 ms (+5.49%; P=0.04), while the VG remained unchanged: 472±15.62 to 474.67±8.74 ms (+0.76%). In the ACMVJ test, the CG increased from 514±37.67 to 520±15.5 ms (+1.42%), while the VG decreased from 515±31.43 to 510.33±16.56 ms (-0.77%). In the 15-seconds jump test, the CG increased from 459±23.48 to 481.6±15.53 ms (+5.15%), while the VG increased from 464±36.66 to 471±33.96 ms (+1.6%). In this same test, the power generated by the CG increased from 20.01±1.84 to 22.14±2.21 W/kg (+11.12%), while the VG increased from 17.28±2.39 to 22.21±5.82 W/kg (+29.7%).

CONCLUSION

WBV has no extra appreciable effect or benefit on the jumping capabilities of high-level female basketball players compared to regular strength training methods.

The traditional maximal lactate steady state test versus the 5 × 2000 m test

Here, we compared the maximal lactate steady state velocity (vMLSS) estimated from a single-visit protocol (v5×2000) to the traditional multi-day protocol (vMLSS). Furthermore, we determined whether there was a lactate steady state during the time limits (Tlim) at vMLSS or v5×2000. Eight runners completed a half marathon (HM), the traditional protocol to determine the vMLSS and the 5×2000 m test in a randomised order, and a Tlim at vMLSS and at v5×2000 in a randomised order. The vMLSS (13.56±0.90 km·h - 1) was higher than the v5×2000 (12.93±0.90 km·h - 1, p=0.001) and comparable to the vHM (13.34±0.75 km·h - 1). The vMLSS (r=0.83) and the v5×2000 (r=0.91) were associated with the vHM but were not indicative of the competition pace. The Tlim at vMLSS (64±15 min) was lower than the Tlim at v5×2000 (94±21 min) and the HM time (95±5 min). In both Tlim, lactate was lower at 45 min than upon finishing the effort and was predictive of its duration (p<0.05). Our results indicate that the 5×2000 m test can be equally useful to assess runners as the traditional MLSS protocol and that there is no lactate steady state during the Tlim at vMLSS or at v5×2000.

Cardiorespiratory fitness and adiposity in overweight and nonoverweight 8-year-old school children

AIM

The objective of the present study was to determine relationship between cardiorespiratory fitness and body fatness in both nonoverweight and overweight 8-year-old school children.

METHODS

The study participants were a 245 healthy second-grade elementary school children aged 8.9 ± 0.4 yrs (125 boys, 120 girls). Anthropometric data (height, body mass, waist circumference, five skinfold thickness) were collected and body fat percentage was calculated. Body Mass Index (BMI) sex- and age-specific cutoff points were used for overweight and obesity definition and children were placed in two groups: overweight/obese and nonoverweight. Aerobic fitness was assessed with the multistage shuttle-run fitness test. Subjects were grouped into high (upper two quintiles) and low (lower two quintiles) aerobic fitness based on age and sex distributions.

RESULTS

BMI, waist circumference, five skinfold thicknesses and total body fat were lower in overweight and obese children with high aerobic fitness in comparison with youths at the same BMI category with low fitness level (P < 0.01). The beneficial effect of high aerobic fitness was also presented in nonoverweight children (P < 0.01). Finally, aerobic fitness was moderately correlated with total body fat in the whole group of subjects (r = -0.48, P < 0.01).

CONCLUSION

Indicators of local and total adiposity were lower in overweight and obese children with high aerobic fitness. Being fit may reduce the hazards of obesity in population of 8-year-old school children.

Upper body aerobic fitness comparison between two groups of competitive surfboard riders

The aim of the present study was to evaluate and compare the upper-body aerobic fitness characteristics in 2 groups of competitive surfers with different performance levels. Thirteen male competitive surfers performed an incremental dry-land board paddling test to determine specific peak oxygen uptake (VO2peak), peak power output (Wpeak) and the exercise intensity (%VO2peak) that elicits a blood lactate concentration of 4 mmol x L(-1) (LT4). As a measure of surfing performance, surfers were ranked according to their competitive season performance (RANK) and divided into 2 groups based on their performance level; European top-level competitive surfers (ELS) (n = 7) and regional level competitive surfers (RLS) (n = 6). ELS reached significantly higher values than RLS for Wpeak (154.71 +/- 36.82 W vs. 117.70 +/- 27.14 W: P = 0.04) and LT4 (95.18 +/- 3.42 %VO2peak vs. 88.89 +/- 5.01 %VO2peak; P = 0.02) but not VO2peak (3.34 +/- 0.31 L x min(-1) vs. 3.40 +/- 0.37 L x min(-1); P = 0.77). Spearman-rank order correlation analysis revealed that RANK was inversely correlated with Wpeak (r = -0.65, P = 0.01) and LT4 (r = -0.58, P = 0.03). These findings identify that better surfers have higher upper body aerobic fitness scores.

Blood lactate and heart rate during national and international women's basketball

AIM

In order to measure game intensity in female basketball players, 2 teams (Olympic National Team - I -and a team at 1(st) National Division - N) were studied for a total of 12 games (10 official competitions and 2 practice games -P).

METHODS

Both blood lactate concentration ([La](b)) and mean heart rate (HR) were measured during the games and then compared with a progressive field test where maximal blood lactate (max[La](b)), individual lactate threshold and maximal heart rate (HR max) values were obtained. All different categories (International, National and Practice) and positions (Guard, Forward and Center) were taken into account in this study.

RESULTS

Differences (p<0.05) in HR were found between all positions (Guard=185+/-5.9; Forward=175+/-11 and Center=167+/-12 beats x min(-1)) and between the International team and the rest of the categories (International=186+/-6; National=175+/-13 and Practice=170+/-11 beats x min(-1)). The [La](b) differed between the Guard and the other 2 positions (Guard=5.7+/-2.1; Forward=4.2+/-2.1 and Center=3.9+/-2.0 mmol x L(-1)) and between Practice and the rest of the categories (International=5.0+/-2.3; National=5.2+/-2.0 and Practice=2.7+/-1.2 mmol x L(-1)). The game intensity of International players reached 94.6% of their maximum HR value, whereas National players reached 90.8%, this percentage descending to 89.8% during Practice. International games reached the individual lactate threshold at 89.2% of the maximum HR; National games at 88.6%.

CONCLUSION

We can conclude that the game intensity of female basketball increases according to the level of competition. It may also differ according to playing position, being greatest in guards. The game intensity at international level surpasses the individual lactate threshold, whereas it reaches a lower level in training games.

Physiological differences and rating of perceived exertion (RPE) in professional, amateur and young cyclists

BACKGROUND

The aim of this study is to measure and compare the physiological characteristics and the rating of perceived exertion (RPE) in 72 high level road cyclists of 3 different categories.

METHODS

These cyclists were divided in 3 groups according to their age (24 professionals, mean age 26 years, 22 amateurs, 22 years and 26 juniors, 18 years).

MEASURES

they carried out a progressive test to exhaustion in a specific cycloergometer, starting with a power output of 100 watts and increasing 50 watts each 4 min. VO2 was measured continuously. At the end of each one of the 4 min steps the subject was asked about his RPE using the 6-20 Borg's scale.

RESULTS

Professional cyclists showed a VO2max, VO2 x kg(-1) and a maximum power output significant higher than other groups, while there were no significant differences between amateurs and juniors. VO2 and RPE were significantly different, in all the categories, during high work loads. No significant differences were found between RPE and %VO2max. RPE and heart rate (HR) were significantly different between professionals and juniors. RPE and %HR max were significantly different with low loads, but no with high loads. In the same way, RPE/w and RPE/(w x kg(-1) were significantly different in all categories.

CONCLUSIONS

We conclude that professional road cyclists reached a VO2max, VO2max x kg(-1) and a maximum power higher than the other categories; so, therefore, these parameters are good as performance indicators, and RPE is of practical value to prescribe exercise training intensities in each category.

The response of sexual and stress hormones of male pro-cyclists during continuous intense competition

The aim of this study was to compare hormonal changes in plasma total testosterone (T), cortisol (C), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (P) in two world-class teams, both consisting of 9 top male pro-cyclists, during a real sports situation (the 1998 "Vuelta a España", a 3-week multi-stage international cycling competition). Venous blood samples were taken the day before the race (S0), after 1 week (S1), after 2 weeks (S2) and at the end of the race (S3). The S0 T level was significantly lower in the team with more racing days in the previous month. There was a significant basal T decrease (p < 0.05) during the race in comparison with the initial value, in spite of the difference in S0 T level between teams. However, there was no difference between teams in the mean decrease in T level. C decreased significantly between S0 and S1 and between S1 and S2, but not between S2 and S3. There were no differences in P concentration between teams or throughout the study, except for a significant increase between S2 and S3. There were no initial differences in LH nor FSH concentration between the teams, nor at any of the study follow-up times. We conclude that in professional top-level athletes S0 T values depend on the number of competition days of the previous month. We observed a similar decrease in the T levels in both teams, independent of the absolute S0 values. In both teams C decreased during long-lasting cycling competition.

Thyroid hormone levels during a 3-week professional road cycling competition

AIMS

The aim of this investigation was to examine the thyroid hormone levels of professional cyclists during a 3-week stage competition (Vuelta a España 1998).

METHODS

The study population was made up of 16 male cyclists from two world-leading professional teams. Four blood samples were drawn (between 07:00 and 09:00 a.m.) from each participant before and at the end of the 1st, 2nd and 3rd weeks of competition. 3,5,3'(-Triiodothyronine (T(3)), free T(3) (FT(3)), thyroxine (T(4)), free T(4) (FT(4)) and thyroid-stimulating hormone (TSH) were determined in each blood sample by radioimmunoassay.

RESULTS

Serum T(4), FT(4) and FT(3) levels showed a significant increase (p < 0.05) by the last week of competition while concentrations of TSH and T(3) remained unchanged.

CONCLUSION

In conclusion, 3 weeks of competition provokes changes in basal thyroid hormone concentrations in professional road cyclists.

Left ventricular mass index and sports: the influence of different sports activities and arterial blood pressure

BACKGROUND

The mechanisms by which endurance training produces physiological hypertrophy have been thoroughly investigated but not with young athletes. The aim of our study was to investigate arterial blood pressure exercise responses in young athletes who started heavy training by the age of 11, participating in metabolically different sports (cycling, kayaking, and soccer) and to analyse the influence that arterial blood pressure at maximum exercise and VO(2) max could have on the development of cardiac mass in these subjects.

SUBJECTS AND METHODS

We studied a group of well trained normotensive male subjects, comprising 37 cyclists, 15 soccer players and 12 canoeists (mean age, 16+/-1 years). Evaluation included a clinical history and physical examination, M-mode and two-dimensional echocardiography, 12-lead resting electrocardiogram and a graded exercise test with direct determination of VO(2) max. Systolic and diastolic blood pressure were measured at rest and maximum exercise. Determination of the left ventricular mass index (LVMI) was performed using Devereux's formula with correction for the body surface area.

RESULTS

Cyclists showed values of LVMI in g m(-2) significantly higher than those of other subjects (123 vs. 92 and 113). Canoeists showed the maximal arterial blood pressure at maximum exercise in mmHg (190 vs. 172 and 170) and cyclists showed the maximal VO(2) ml kg(-1) min(-1) uptake (57.6 vs. 48.5 and 53.3). A linear correlation was found between LVMI and VO(2) max (r=0.4727, P<0.001) and this correlation was also significant with systolic blood pressure at maximum exercise (r=0.2909, P<0.01). No differences in LVMI were found when comparing those subjects who presented systolic blood pressure at maximum exercise equal or greater than 195 mmHg with those who presented less than this value.

CONCLUSIONS

It can be concluded that VO(2) max is the variable that better correlates with the LVMI. Athletes who reach greater systolic blood pressures at peak exercise have a tendency to develop greater LVMI. In comparison with soccer players and canoeists, cyclists are the sportsmen who develop a greater LVMI and VO(2) max.

Intensity of exercise during road race pro-cycling competition

PURPOSE

The aim of this study was to quantify the intensity of competition during two professional bicycle stage races: the Tour de France (Tour) and Vuelta a España (Vuelta).

METHODS

The HR responses of 18 world class cyclists were recorded during the races and compared with HR ranges that corresponded to four intensities of exercise that were measured in the laboratory with an incremental test to exhaustion 2 wk before each race. The four intensities were: Anaerobic (AN) over the individual anaerobic threshold, which was over 90% of VO2max; intense aerobic (IA), which was between 70 and 90% of VO2max; moderate aerobic (MA), which was between 50 and 70% of VO2max; and recovery (RE), which was < 50% of VO2max. The stages were divided in individual time trial (ITT), flat, or mountain.

RESULTS

The mean HR of the Vuelta and Tour were, respectively, 133.8 +/- 17.9 and 134 +/- 18.6 beats x min(-1). The mean total time of each stage was 269.6 +/- 122 and 259.4 +/- 119.9 min. The mean stage time over IAT was 17.5 +/- 15.7 and 24.7 +/- 26 min; the IA time was 75.2 +/- 47.6 and 79.6 +/- 48.3 min; the MA was 97.2 +/- 57.4 and 89.5 +/- 54.9 min. Finally the RE time was 79.6 +/- 60.5 and 65.4 +/- 69.7 min. The percentage of participation related to total time of the race was, respectively, in the Vuelta and the Tour, 12.99 and 16.8% in AN exercise intensity, 29.5 and 29.2% in IA, 32.4 and 31.9% in MA, and 25.1 and 25.2% in RE. There are no differences in AN time among flat, mountain, and ITT stages in each race, except for the mountain stages in the Tour.

CONCLUSION

Cycling is a high intensity sport because approximately 93 min in flat and 123 min in mountain stages were above 70% of VO2max. In addition, the time spent at IAT was roughly 20 min regardless of stage type, suggesting that the anaerobic capacity limits performance.

Genetic variation in the renin-angiotensin system and athletic performance

The D allele at the angiotensin-I-converting enzyme (ACE)-insertion/deletion polymorphism has been associated with an increased risk of developing several pathological processes, such as coronary heart disease and ventricular hypertrophy. Individuals with the DD genotype show a significantly increased left-ventricular mass in response to physical training, compared to the II genotype (which would be associated with the lowest plasma ACE levels) and the ID genotype. The II genotype has been linked to a greater anabolic response. In accordance with a role for ACE in the response to rigorous physical training, a higher frequency of the I allele has been reported to exist among elite rowers and high-altitude mountaineers. Sixty elite (professional) athletes (25 cyclists, 20 long-distance runners, and 15 handball players), and 400 healthy controls were genotyped for the DNA polymorphisms of the ACE, angiotensinogen (Ang) and angiotensin receptor type 1 (AT1) genes. Plasma ACE levels showed a strong correlation with the I/D genotype in our population. The I-allele occurred at a significantly higher frequency in athletes compared to controls (P = 0.0009). Gene and genotype frequencies for the Ang and AT1 polymorphisms did not differ between athletes and controls. Since the frequency of the ACE I allele was significantly increased among our elite athletes, we conclude that the ACE polymorphism represents a genetic factor that contributes to the development of an elite athlete.

Comparison of dietary intake and eating behavior of professional road cyclists during training and competition

The dietary intake and eating behavior of a group of professional elite road cyclists during high intensity training and competition was compared. Their eating pattern consisted of several snacks throughout the race or training, a meal eaten no later than 1 hr postexercise, supper, and breakfast. Protein intake showed a significant difference between evaluation times expressed in three ways: per total amount intake, by kg body weight, and percentage of energy supplied. Due to the high energy intake of these cyclists during training and competition (22.9 +/- 1.5, 22.4 +/- 1.7 MJ, respectively) they presented a high consumption of each macronutrient both in competition and in training. The eating behavior of these athletes was similar during breakfast (possibility to choose from among approximately 25 foods) and supper (set menu), with variation in the energy intake and a similar relative contribution of the different macronutrients. In general, it is possible to consider the professional road cyclists as a homogeneous group with a similar nutrition intake, eating habits, and nutritional needs throughout the more demanding periods of the season. Furthermore, differences found in protein intake between periods could not be explained by differences in the food available in competition and training periods.

Importance of wash riding in kayaking training and competition

PURPOSE

The use of different wash-riding techniques is common during kayak training and competition. Changes in wash-riding positions could imply a different exercise intensity. The aim of this study, therefore, was to quantify the energy savings made when a kayaker is "wash riding."

METHODS

Eight male international flat water kayakers, who performed a field test of 2000 m in each of the four wash-riding positions, head (H), right wave (RW), left wave (LW), and end position (V), were studied. The data investigated were: time, stroke rate, blood lactate (BL), heart rate (HR), and rate of perceived exertion (RPE). Under laboratory conditions kayakers performed the same intensity of exercise in a kayak ergometer, and HR, oxygen uptake (VO2), BL, mean power output (W), and RPE were measured.

RESULTS

The results show significant differences (P < 0.05) among H, RW/LW, and V. The mean values for BL (P < 0.05) were 4.2, 2.0, 2.2, and 1.5 mmol.L-1, for H, RW, LW, and V, respectively. RPE also revealed differences, with values of 15, 12.6, 12.6, and 9.7 for H, RW, LW, and V, respectively. Mean power output gave values of 190.3 (H), 155.6 (RW and LW), and 129.5 (V) W. HR was different between H and V (172 and 151), while stroke rate was different among the parameters H, RW, and V (93.7, 88.8, and 87.6, respectively). The VO2 in the kayak ergometer test showed a difference between H and V (3.78 and 2.23 L.min-1).

CONCLUSIONS

We conclude that "wash riding" involves a saving in energy cost of between 18% and 31.9%, depending on the position. This conclusion is of importance for the quantification and calibration of kayak training and competition.

Macronutrients intake of top level cyclists during continuous competition--change in the feeding pattern

In order to quantify the nutritional status and the feeding pattern of professional cyclists during continuous competition, food intake was accurately measured and recorded using the weighed inventory of food (over three 24 h periods) during all meals in ten top professional cyclists during a real 3 weeks' competition. A 24 h period was defined as the time between the start of one stage and the next start. The 24 h period intake of energy, protein, fat, and carbohydrate was used to discover whether these intakes met requirements for endurance exercise. The average intake of energy and macronutrients was: energy = 23.5 +/- 1.8 MJ/24 h period, carbohydrate = 841.4 +/- 66.2 g/ 24h period; protein = 201.8 +/- 17.7g/24 h period; and fat = 158.6 +/- 16.3 g/24 h period. The carbohydrate, protein and fat contribution to energy was 60.0%, 14.5%, and 25.5% respectively. Fluid intake per 24h period was 3.29 +/- 0.94l (1.26 +/- 0.55 l during the race). Our study shows a similar energy intake in comparison with the only previous study in 1989 but there is a change in the feeding pattern of top level cyclists. A more important role is given to the intake of carbohydrate just after competitions together with an increase in protein intake. Both changes could have a positive effect on performance.

Adaptation of the lumbar spine to different positions in bicycle racing

STUDY DESIGN

A radiologic and electromyographic study was done of the adaptation of the lumbar spine to high-performance cycling.

OBJECTIVES

To evaluate changes in the lumbar spine produced by different cycling positions on different types of bicycles used during competition.

METHODS

Three professional cyclists were observed to evaluate changes in the lumbar spine. Radiographs were obtained of the different positions adopted by the cyclists during competition, and changes in the angles of the lumbar spine were measured. An electromyographic study was done of the abdominal, lumbar, and thoracic paravertebral muscles.

RESULTS

The cyclists' positions involved a change from discal lordosis to kyphosis. To obtain a more aerodynamic position, the cyclists flexed the hip and made the pelvis horizontal without changing disc angles. The contraction of paravertebral lumbar muscles was proportional to pedalling intensity and decreased in more aerodynamic positions. The tone of the paravertebral thoracic muscles depended on the extent of cervical hyperextension. Abdominal muscles remained relaxed in all bicycle positions and with all pedalling intensities.

CONCLUSIONS

The changes observed could modify the normal biomechanics of the lumbar spine, but the overall mechanical load on the spine is reduced by shifting weight onto the upper limbs. The imbalance that occurs between the activity of flexor and extensor muscles could cause lumbar pain in persons without proper physical preparation.

Aldosterone levels and cardiac hypertrophy in professional cyclists

Aldosterone has been associated with the development of cardiac hypertrophy and a correlation has been found between levels of aldosterone and the degree of cardiac hypertrophy in hypertensive patients. Our study aimed to test the relation between physiologic cardiac hypertrophy and serum aldosterone in a group of highly trained cyclists. Determination of the left ventricular mass index (LVMI) was performed in a group of 40 professional cyclists by using Devereux's formula with correction for body surface area. After an overnight fast, blood samples were collected and serum aldosterone levels were measured using RIA. LVMI and serum aldosterone were intercorrelated using linear regression analysis. Twenty-three of the 40 cyclists (58%) presented an LVMI > 130 g.m-1 and the other 17 subjects (42%) presented an LVMI < 130 g.m-1. Serum aldosterone levels did not correlate with LVMI in either of the groups (LVMI > 130 g.m-1, r = -0.089; LVMI < 130 g.m-1, r = 0.146). The lack of correlation of this hypertrophy with serum aldosterone levels suggests that physiologic hypertrophy of the athlete's heart could be caused by a different stimulus to that seen in pathologic hypertrophy of hypertensives.

Prevalence and upper limit of cardiac hypertrophy in professional cyclists

The term athlete's heart refers to an increased left ventricular mass. Few studies have assessed the prevalence and normal upper limit of cardiac hypertrophy in highly trained cyclists and this was the aim of this study. A group of 40 professional road cyclists [mean age 26 (SD 3) years] who had participated in European competitions for 3-10 years, were evaluated at the beginning of the 1992-93 season. Evaluation included a clinical history and physical examination, one and two-dimensional echocardiography, 12-lead resting electrocardiogram and a graded exercise test. Determination of the left ventricular mass index (LVMI) was performed using Devereux's formula with correction for the body surface area. Systolic and diastolic blood pressure were measured at rest and at peak exercise. Of the group 23 cyclists (58%) presented a LVMI greater than 130 g.m-2, 21 cyclists presented a diastolic ventricular thickness equal to or greater than 13 mm, with a superior limit of 19 mm; 3 cyclists presented asymmetrical septum hypertrophy; and the relationship between posterior wall and left ventricular diastolic radius was equal to or greater than 0.45 in 14 cases (35%). Electrocardiographic abnormalities of ST-T segment were seen in only 1 subject. No correlation was found between the degree of ventricular hypertrophy and arterial blood pressure. We concluded that these professional cyclists showed a high prevalence of cardiac hypertrophy (58%). The distribution of this hypertrophy was concentric in 20/33 and asymmetric in 3/23 of the subjects with left ventricular hypertrophy. The electrocardiograms were normal in 98% of the subjects.

Aerobic exercise capacity at sea level and at altitude in Kenyan boys, junior and senior runners compared with Scandinavian runners

The aim of this study was to characterize Kenyan runners in regard to their oxygen uptake and blood and ammonia responses when running. Untrained Kenyan boys (14.2 +/- 0.2 years) and Scandinavian runners were included for comparison. The studies were performed at altitude (approximately 2.000 m.a.s.l.) and, for several Kenyan and Scandinavian runners, at sea level as well. At altitude sedentary adolescent Kenyan boys had a mean maximal oxygen uptake (VO2max) of 47 (44-51) ml.kg-1.min-1, whereas similarly aged boys regularly walking or running but not training for competition reached above 62 (58-71) ml.kg-1.min-1 in VO2max. Kenyan runners in active training had 68 +/- 1.4 ml.kg-1.min-1 at altitude and 79.9 +/- 1.4 ml.kg-1.min-1 at sea level, with individuals reaching 85 ml.kg-1.min-1. The best Scandinavian runners were not significantly different from the Kenyan runners in VO2max both at altitude and at sea level, but none of the Scandinavians reached as high individual values as observed for some Kenyan runners. The running efficiency, determined as the oxygen cost at a given running speed, was less in the Kenyan runners, and the difference became more pronounced when body weight was expressed in ml.kg-0.75 min-1. Blood lactate concentration was in general lower in the Kenyan than in the Scandinavian runners, and the Kenyans also had extremely low ammonia accumulation in the blood even at very high exercise intensities. It is concluded that it is the physical activity during childhood, combined with intense training as teenagers that brings about the high VO2max observed in some Kenyan runners. Their high aerobic capacity, as well as their good running economy, makes them such superior runners. In addition, their low blood lactate and ammonia accumulation in blood when running may also be contributing factors.

Morphology, enzyme activities and buffer capacity in leg muscles of Kenyan and Scandinavian runners

The study comprises data on 12 Scandinavian runners who had either trained for two weeks in Kenya (n = 6; approximately 2000 meters above sea level (m.a.s.l.)) or in Portugal (n = 6; sea level (s.l.)) and on 13 Kenyan runners (9 junior and 4 senior) living and training at approximately 2000 m.a.s.l. Muscle biopsies were taken before and after the training camps in the Scandinavian runners and once on the Kenyan runners from the vastus lateralis (v.l.) and the gastrocnemius muscles. Muscle fiber size and composition were similar in the various groups (4.6-5.1 X 10(3) microns2; ST approximately 60-70%; FTa 30-40%; FTb < 6.0%) with a tendency for some more (approximately 5%) FTa fibers in the gastrocnemius muscle. Mean number of capillaries in v.l. varies between 405-493 cap.(mm2)-1, 2.0-2.7 cap.fiber-1, and 4.4-6.2 cap around the various fiber types, with the Kenyan seniors having the highest and the Kenyan juniors the lowest values. All runners had 10-20% more capillaries in their gastrocnemius muscle. Similar levels for citrate synthase (CS) activity were found in the v.l. of the Kenyan seniors and Scandinavian runners, whereas the Kenyan juniors were 10-15% lower. The 3- hydroxyacyl-CoA-dehydrogenase (HAD) activity was 20% higher in the Kenyan than in the Scandinavian runners. In the gastrocnemius muscle, both enzyme activities were 20-50% higher in Scandinavian and Kenyan runners. The ratio for lactate dehydrogenase (LDH) isoform1-2 and isoform4-5 was increased when training at altitude due to a lowering of LDH4-5 and became close to what was observed in the Kenyan runners.

Exercise in the heat: strategies to minimize the adverse effects on performance

Exercise in the heat is usually associated with reduced performance; both dehydration and hyperthermia adversely affect mental and physical performance. For athletes from temperate climates, the negative effects of heat had humidity can be attenuated by a period of acclimatization. This requires up to 10-14 days. Endurance-trained individuals already show some of the adaptations that accompany acclimatization, but further adaptation occurs with training in the heat. Prior dehydration has a negative effect even on exercise of short duration where sweat losses are small. The athlete must begin exercise fully hydrated and regular ingestion of fluids is beneficial where the exercise duration exceeds 40 min. Dilute carbohydrate-electrolyte (sodium) drinks are best for fluid replacement and also supply some substrate for the exercising muscles. Post-exercise rehydration requires electrolyte as well as volume replacement. In extreme conditions, neither acclimatization nor fluid replacement will allow hard exercise to be performed without some risk of heat illness.

Melatonin and gonadotropin hormones in pubertal sportsgirls

In order to determine the influence of physical training on menstrual disturbances in sportsgirls, the levels of luteinizing hormone (LH), follicle stimulating hormone (FSH) and melatonin have been studied in young athletes of track and field speciality using the Cooper test. Basal hormone levels and anthropometric data were also studied in age matched control girls. No significant differences in LH, FSH and melatonin hormone concentrations were observed between the PRE and POST Cooper test. However, significantly lower basal levels of LH were found in the early follicular phase or luteal phase of sportsgirls when contrasted with the control girls. No differences in FSH levels were observed in the early follicular phase of sportsgirls but higher FSH levels were found in the luteal phase. Daytime melatonin levels of sportsgirls were significantly higher than those in control girls. Age and anthropometric parameters studied showed no differences in height, weight, tricipital skinfold and percentage of body fat, but abdominal and subescapular skinfold measures were greater in control girls than in sportsgirls. It appears that continuous physical training can produce alterations in antireproductive hormone secretion such as melatonin, which can play an inhibitory role on the menstrual cycle hormone patterns in sportsgirls.

Altitude training and muscular metabolism

To study the effects of training at moderate altitude on muscle metabolism; we defined the lowest altitude which affected the aerobic capacity in man, and we studied the differences between training at an altitude of 2300 m and at sea level, both at the same relative (to the VO2max) and absolute intensity of work. We confirmed that at 1200 m the VO2max is decreased in sedentary and well-trained persons. Elite athletes already at 900 m decrease their VO2max. We have found an increase in myoglobin, oxidative enzyme activities and endurance capacity and a decrease in some glycolytic enzyme activities associated with simulated altitude training. We conclude that when the amount of training performed at altitude is similar to the amount at sea level, the stimulus of hypoxia associated with the training stimulus induces improvements in the muscle oxidative enzymes and myoglobin.

Is hypoxia a stimulus for synthesis of oxidative enzymes and myoglobin?

To compare two situations with similar magnitudes of mitochondrial substrate flux but different blood oxygen contents, one-legged training was employed. Ten healthy subjects trained one leg under normobaric conditions and the other under hypobaric conditions. At each session the subjects trained each leg for 30 min. The absolute work intensity was the same for both legs and was chosen to correspond to 65% of the average (right and left) pretraining one-legged maximal work capacity. There were three to four training sessions per week for 4 wk. Muscle biopsies from each leg were taken before and after training and analyzed for fiber types, capillaries, myoglobin, and oxidative and glycolytic enzymes. The most striking finding was a greater increase of citrate synthase activity under hypobaric conditions than under normobaric conditions. In addition, the myoglobin content increased in the leg trained under hypobaric conditions, whereas it tended to decrease in the normobarically trained leg. Because both legs were trained at the same intensity, the oxygen turnover and the substrate flux through the carboxylic acid cycle and the respiratory chain must have been of similar magnitude. Thus a difference in substrate flux is less likely to have caused the differences in enzyme activities and myoglobin content between training under normobaric and hypobaric conditions. Instead, the stimulus seems to be related to the blood oxygen content or tension.

Effects of training at simulated altitude on performance and muscle metabolic capacity in competitive road cyclists

Differences between the effects of training at sea level and at simulated altitude on performance and muscle structural and biochemical properties were investigated in 8 competitive cyclists who trained for 3-4 weeks, 4-5 sessions/week, each session consisting of cycling for 60-90 min continuously and 45-60 min intermittently. Four subjects, the altitude group (AG), trained in a hypobaric chamber (574 torr = 2300 m above sea level), and the other four at sea level (SLG). Before and after training work capacity was tested both at simulated altitude (574 torr) and at sea level, by an incremental cycle ergometer test until exhaustion. Work capacity was expressed as total amount of work performed. Venous blood samples were taken during the tests. Leg muscle biopsies were taken at rest before and after the training period. AG exhibited an increase of 33% in both sea level and altitude performance, while SLG increased 22% at sea level and 14% at altitude. Blood lactate concentration at a given submaximal load at altitude was significantly more reduced by training in AG than SLG. Muscle phosphofructokinase (PFK) activity decreased with training in AG but increased in SLG. All AG subjects showed increases in capillary density. In conclusion, work capacity at altitude was increased more by training at altitude than at sea level. Work capacity at sea level was at least as much improved by altitude as by sea level training. The improved work capacity by training at altitude was paralleled by decreased exercise blood lactate concentration, increased capillarization and decreased glycolytic capacity in leg muscle.

Effect of hyperthyroidism on fibre-type composition, fibre area, glycogen content and enzyme activity in human skeletal muscle

Seven hyperthyroid patients were studied by repeated muscle biopsies (vastus lateralis) before and after a period of medical treatment which averaged 10 months. The biopsies were analysed with regard to fibre-type composition, fibre area, capillary density, glycogen content and enzyme activities representing the glycolytic capacity (hexokinase, 6-phosphofructokinase), oxidative capacity (oxoglutarate dehydrogenase, citrate synthase) and Ca2+- and Mg2+-stimulated ATPase in muscle. In the pretreatment biopsy (hyperthyroid state), there was a significantly lower proportion of type I fibres (30% vs. 41%), a higher capillary density (23%), lower glycogen content (33%), and higher hexokinase activity (32%) compared with the post-treatment biopsy. No significant changes in the activity of the remaining enzymes were observed. The present study indicates that hyperthyroidism induces a transformation from type I to type II fibres in human skeletal muscle. The increase in hexokinase activity probably reflects a higher glucose utilization by skeletal muscle in order to compensate partially for the reduced glycogen content.