Biomedical subjects

I Mujika

Publications and source records attributed to I Mujika.

32 records · Page 2Linked to original sources

PubMed1999

Level ground and uphill cycling ability in professional road cycling.

PURPOSE: To evaluate the physiological capacities and performance of professional road cyclists in relation to their morphotype-dependent speciality. METHODS: 24 world-class cyclists, classified as flat terrain (FT, N = 5), time trial (TT, N = 4), all terrain (AT, N = 6). and uphill (UH, N = 9) specialists, completed an incremental laboratory cycling test to assess maximal power output (Wmax), maximal oxygen uptake (VO2max), lactate threshold (LT), and onset of blood lactate accumulation (OBLA). RESULTS: UH had a higher frontal area (FA):body mass (BM) ratio (5.23 +/- 0.09 m2 x kg(-1) x 10(-3)) than FT and TT (P < 0.05). FT showed the highest absolute Wmax (481 +/- 18 W), and UH the highest Wmax relative to BM (6.47 +/- 0.33 W x kg(-1)). WLT and W(OBLA) values were significantly higher in FT (356 +/- 41 and 417 +/- 45 W) and TT (357 +/- 41 and 409 +/- 46 W) than in UH (308 +/- 46 and 356 +/- 41). Scaling of these values relative to FA and BM exponents 0.32 and 0.79 minimized group differences, but considerable differences among mean group values remained. FT and TT had the highest Wmax per FA unit (1300 +/- 62 and 1293 +/- 57 W x m2), whereas TT had the highest absolute W x kg(-0.32) and W x kg(-0.79), as well as W x kg(-0.32), W x kg(-0.79), and W x m2 at the LT and OBLA. CONCLUSIONS: i) Scaling of maximal and submaximal physiological values showed a performance advantage of TT over FT, AT, and UH in all cycling terrains and conditions; and ii) mass exponents of 0.32 and 1 were the most appropriate to evaluate level and uphill cycling ability, respectively, whereas absolute Wmax values are recommended for performance-prediction in short events on level terrain, and W(LT) and W(OBLA) in longer time trials and uphill cycling.

Adult↗

PubMed1999

Anaemia and iron deficiency in athletes. Practical recommendations for treatment.

Trained athletes frequently experience low levels of blood haemoglobin (13 to 14 g/100ml in men and 12 g/100ml in women) plus low haematocrit and low ferritin levels. These parameters define the concept of 'sports anaemia'. Low iron levels may be due to mechanical haemolysis, intestinal bleeding, haematuria, sweating, low iron intake or poor intestinal absorption. The resulting decrease in blood gas transport and muscle enzyme activity impairs performance. The concept of sports anaemia can be criticised. Simply measuring the blood levels does not take into account the haemodilution that occurs in athletes because of training. The lack of these measurements makes it difficult to diagnose anaemia or evaluate any treatment. Anaemia is treated by preventing decreased iron stores through a balanced food intake or iron supplements. Self-medications must be discouraged because of intolerance, risk of overdose and many other drug interactions.

Altitude↗

PubMed1998

The influence of training characteristics and tapering on the adaptation in highly trained individuals: a review.

In the general population, the adaptation to training seems to be dependent on factors such as training intensity, volume and frequency, and the initial level of fitness. In highly trained athletes, however, training intensity and initial performance level appear to be the most important factors influencing the response to training, and therefore competition performance, provided that necessary training volume and frequency are assured. When preparing for a major competition, athletes tend to reduce their training load for a variable period of time. This technique, known as taper, can have a major influence on the athlete's performance. The response to taper may be affected by the degree to which training intensity, volume and frequency are reduced, as well as by the combined effects of these variables. A thorough review of the available literature suggests that training volume and frequency can be reduced to a higher extent than training intensity, if falling into detraining is to be avoided. Moreover, the duration of the taper period and the time constant of decay of the training load can also affect the response to taper. Indeed, slow progressive reductions appear to be more effective than sudden standardized reductions in improving the athlete's performance level.

Adaptation, Physiological↗

PubMed1998

A new reliable laboratory test of endurance performance for road cyclists.

PURPOSE: The purpose of this study was to devise and evaluate a laboratory test of cycling performance that simulates the variable power demands of competitive road racing. The test is a 100-km time trial interspersed with four 1-km and four 4-km sprints. METHODS: On three occasions separated by 5-7 d, eight endurance-trained cyclists (peak oxygen uptake 5.0 +/- 0.7 L.min-1, peak power output 411 +/- 43 W, mean +/- SD) performed the test on their own bikes mounted on an air-braked Kingcycle ergometer. Subjects were free to regulate their power output but were asked to complete each sprint and the full distance as quickly as possible. The only feedback given to the cyclists during each test was elapsed distance. RESULTS: In the first test, time for the 100 km and mean times for the 1-km and 4-km sprints were 151:42 +/- 10:36, 1:16 +/- 0:06, and 5:31 +/- 0:16 min:s, respectively; these times improved by 1.6-2.2% in the second test, but there was little further improvement in the third test (0.7 to -0.5%). The between-test correlation for 100-km time was 0.93 (95% CI 0.79 to 0.98), and the within-cyclist coefficient of variation was 1.7% (95% CI 1.1 to 2.5%). Mean sprint performance showed similar good reliability (within-subject variation and correlations for the 1-km and 4-km sprint times of 1.9%, 2.0%, 0.93, and 0.81, respectively). CONCLUSIONS: The high reliability of this laboratory test will make the test useful for research on performance of competitive road cyclists.

Adult↗

PubMed1998

Hematological responses to training and taper in competitive swimmers: relationships with performance.

The purpose of this study was to monitor hematological changes during 12 weeks of intense training and 4 weeks of taper in 8 highly trained competitive swimmers, and to assess the relationships between hematological variables and competition performance. Venous blood samples were obtained in the mid-season (wk 10), before taper (wk 22) and after taper (wk 26). Swimmers participated in actual competitions within 1 wk of each blood testing. Comparisons were made between swimmers improving performance with taper by more than 2% (n = 4), efficient (GE) or less than 2% (n = 4), less efficient (GLE). Hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) increased significantly during training. MCH and MCHC decreased during taper, while serum iron tended to increase (P = 0.07). Improvement in performance during taper was positively correlated with post-taper red cell count (RCC): r = 0.83, P < 0.05. GE swimmers had higher pre- and post-taper RCC, and post-taper Hb and hematocrit. In conclusion, intense training and taper appeared to influence the hematological status and performance capacity of the studied group of swimmers.

Adult↗

PubMed1997

Creatine supplementation as an ergogenic aid for sports performance in highly trained athletes: a critical review.

Creatine supplementation has become a common practice among competition athletes participating in different sports over the last few years. The mechanism by which supplementary creatine could have potential ergogenic effects would be an increased muscle creatine and phosphocreatine concentration, leading to a higher rate of ATP resynthesis, a delay in the onset of muscular fatigue and a facilitated recovery during repeated bouts of high-intensity exercise. A critical review of the literature reveals that these ergogenic effects, when found, have been generally shown in untrained subjects performing several exercise bouts under laboratory conditions. The limited body of scientific data available concerning highly trained athletes performing single competition-like exercise tasks indicates that this type of population does not benefit from creatine supplementation. Therefore, the widespread use of creatine ingestion to improve competition performance does not seem to be justified. The potential interest of creatine supplementation for elite athletes could be related to an increased ability to perform repeated high-intensity exercise bouts, either during training or during competition in sports in which repeated efforts are required (e.g. soccer, basketball), but this possibility needs scientific confirmation.

Adenosine Triphosphate↗

PubMed1996

Validity of a velodrome test for competitive road cyclists.

The aim of this study was to evaluate the validity of a velodrome field test consisting of repeated rides of 2,280 m, with an initial speed of 28 km.h-1 and increments of 1.5 km.h-1 interspersed with 1-min recovery periods until exhaustion. A group of 12 male competitive road cyclists performed maximal cycling tests under velodrome and laboratory conditions. Velodrome oxygen uptake (VO2) and power output were estimated using equations previously published. Physiological responses to the two tests were compared. Relationships between performance in the velodrome and physiological parameters measured in the laboratory were studied. Maximal power output, heart rate and VO2 were similar in the velodrome and the laboratory [372 (SD 50) vs 365 (SD 36) W, 195 (SD 8) vs 196 (SD 9) beats.min-1 and 4.49 (SD 0.56) vs 4.49 (SD 0.46) l.min-1, respectively], while maximal velodrome blood lactate concentration was significantly higher [13.5 (SD 2.1) vs 11.8 (SD 3.1) mmol.l-1]. Velodrome heart rate was higher at submaximal exercise intensities representing 40%, 50% and 60% of maximal aerobic power, and velodrome blood lactate concentration was also higher at 60%, 70% and 80% of maximal aerobic power. The laboratory parameter that showed the highest correlation with the maximal cycling speed in the velodrome was maximal oxygen uptake (VO2max) expressed per unit of body mass (r = 0.93). In addition, the accuracy of different methods of estimation of the metabolic cost of cycling, rolling resistance, air resistance coefficients and VO2max were compared. Significant differences were found. In conclusion, the present results indicated the validity of a velodrome test used to estimate maximal aerobic parameters of competitive road cyclists, as long as the estimation is made using established equations. When road cyclists are tested in the laboratory, physiological values should be expressed per unit of body surface area or body mass, to predict more accurately the cyclist's performance level under specific field conditions.

Adult↗

PubMed1996

Blood lactate recovery measurements, training, and performance during a 23-week period of competitive swimming.

The purpose of this study was to relate measurements of blood lactate concentration, performance during a maximal anaerobic lactic test (MANLT) and training loads during a 23-week swimming season. Six elite 200-m freestyle male swimmers [mean age 19.5 (SD 1.6) years, height 184 (SD 5) cm and body mass 77.7 (SD 9.0) kg], participated in the study. The MANLT consisted of four all-out 50-m swims interspersed with 10-s recovery periods. Blood lactate concentrations were determined at 3 and 12-min post-exercise and were performed on weeks 2,6,10,14,18 and 21. Swimmers participated in 200-m freestyle competitions on weeks 1,7,13 and 23 (national championships). During weeks 1-10, training mostly involved aerobic exercise, while during weeks, 11-23, it involved anaerobic exercise. At 3-min and 12-min post-MANLT lactate concentrations varied throughout the season [range from 14.9 (SD 1.2) to 18.7 (SD 1.0) mmol.l-1] but demonstrated non-systematic variations. In contrast, the percentage of mean blood lactate decrease (% [La-]recovery) between min 3 and min 12 of the passive recovery post-MANLT increased from week 2 to 10 with aerobic training and decreased from week 10 to 21 with anaerobic training. The MANLT performance improved continuously throughout the season, while competition performance improved during the first three competitions but declined in the final championships, coinciding with the lowest % [La-]recovery and signs of overtraining, such as bad temper and increased sleeping heart rate. The results of this study indicated that % [La-]recovery could be an efficient marker for monitoring the impact of aerobic and anaerobic training and avoiding overtraining in elite 200-m swimmers.

Adolescent↗

PubMed1996

Hormonal responses to training and its tapering off in competitive swimmers: relationships with performance.

During a winter training season, the effects of 12 weeks of intense training and 4 weeks of tapering off (taper) on plasma hormone concentrations and competition performance were investigated in a group of highly trained swimmers (n = 8). Blood samples were collected and the swimmers performed their speciality in competition at weeks 10 (mid-season), 22 (pre-taper) and 26 (post-taper). No statistically significant changes were observed in the concentrations of total testosterone (TT), non-sex hormone binding globulin-bound-testosterone (NSBT), cortisol (C), luteinising hormone, thyroid stimulating hormone, triiodothyronine, thyroxine plasma catecholamines, creatine kinase and ammonia during training and taper. Mid-season NSBT: C ratio and the amount of training were statistically related (r = 0.82, P < 0.05). Competition performance slightly declined during intense training [0.52 (SD 2.51)%, NS] and improved during taper [2.32 (SD 1.69)%, P < 0.01]. Changes in performance during training and taper correlated with changes in ratios TT: C (r = 0.86, P < 0.01 and r = 0.81, P < 0.05, respectively) and NSBT: C (r = 0.77, P < 0.05 and r = 0.76, P < 0.05, respectively). In summary, these results showed that the monitored plasma hormones and metabolic indices were unaltered by 12 weeks of intense training and 4 weeks of taper. The TT: C and NSBT: C ratios, however, appeared to be effective markers of the swimmers' performance capacities throughout the training season.

Adult↗

PubMed1996

Effects of training and taper on blood leucocyte populations in competitive swimmers: relationships with cortisol and performance.

The effects of 12 weeks of training and 4 weeks of taper on blood leucocyte populations and cortisol were investigated in 8 well-trained competition swimmers. Blood samples were taken at rest in the mid-season (week 10), before taper (week 22) and after taper (week 26). Swimmers improving by more than 2% with taper (N = 4), efficient (GE), were compared with swimmers improving by less than 2% (N = 4), less efficient (GLE). No significant changes were observed in leucocyte subpopulations or cortisol during training. The percentage of neutrophils decreased during taper (p < 0.05). Basophils and the percentage of granulocytes tended to decrease, while lymphocytes tended to increase. The increment in lymphocytes was positively related with the reduction in training volume during taper (r = 0.86, p < 0.05). Cortisol levels did not change with taper and were not related with leucocyte status and kinetics. GE swimmers had higher pre- and post-taper eosinophil counts than GLE swimmers (p < 0.05). Lymphocyte counts in GE tended to be higher, too. Cortisol decreased with taper in GE, while it increased in GLE. In conclusion, taper appeared to have an influence on leucocyte populations, which did not seem to be related with blood cortisol.

Adult↗

PubMed1996

Modeled responses to training and taper in competitive swimmers.

This study investigated the effect of training on performance and assessed the response to taper in elite swimmers (N = 18), using a mathematical model that links training with performance and estimates the negative and positive influences of training, NI and PI. Variations in training, performance, NI, and PI were studied during 3-, 4-, and 6-wk tapers. The fit between modeled and actual performance was significant for 17 subjects; r2 ranged from 0.45 to 0.85, P < 0.05. Training was progressively reduced during tapers. Performance improved during the first two tapers: 2.90 +/- 1.50% (P < 0.01) and 3.20 +/- 1.70% (P < 0.01). Performance improvement in the third taper was not significant (1.81 +/- 1.73%). NI was reduced during the first two tapers (P < 0.01 and P < 0.05, respectively), but not during the third. PI did not change significantly during tapers. Thus, the present results show that the model used is a valuable method to describe the effects of training on performance. Performance improvement during taper was attributed to a reduction in NI. PI did not improve with taper, but it was not compromised by the reduced training periods.

Adult↗

PubMed1996

Creatine supplementation does not improve sprint performance in competitive swimmers.

This study was conducted to examine the effects of creatine (Cr) supplementation on sprint swimming performance and energy metabolism. Twenty highly trained swimmers (9 female, 11 male) were tested for blood ammonia and for blood lactate after the 25-, 50-, and 100-m performance in their best stroke on two occasions 7 d apart. After the first trial, subjects were evenly and randomly assigned to either a creatine (5 g creatine monohydrate 4 times per day for 5 d) or a placebo group (same dosage of a lactose placebo) in a double-blind research design. No significant differences in performance times were observed between trials. Post-exercise blood ammonia concentration decreased in the 50- and 100-m trials in the creatine group and in the 50-m trial in the placebo group. The supplementation period had no effect on post-exercise blood lactate. Therefore, creatine supplementation cannot be considered as an ergogenic aid for sprint performance in highly trained swimmers although adenine nucleotide degradation may be reduced during sprint exercise after 5 d of creatine ingestion.

Adult↗

PubMed1995

Mitochondrial ATP production rate in 55 to 73-year-old men: effect of endurance training.

The effect of 6-week endurance training on mitochondrial ATP production rate was investigated in 14 elderly men. Mean age, body weight and height were 63 +/- 6 yr, 75.6 +/- 9.2 kg and 174 +/- 4 cm, respectively. Subjects trained on a Monark cycle ergometer at 79 +/- 8% of their maximal heart rate for 1 h day-1, 4 days week-1. Muscle samples were obtained at rest, before and after endurance training, by a needle biopsy technique and used for determination of mitochondrial ATP production rate in isolated mitochondria and enzyme assays. Endurance training resulted in a significant increase in maximal oxygen uptake (L min-1) (P < 0.01). Citrate synthase activity, a mitochondrial marker enzyme, and hexokinase activity increased significantly (both P < 0.01) in response to training while 3-hydroxyacyl-CoA dehydrogenase and carnitine palmitoyltransferase I activities remained statistically unchanged. A higher mitochondrial ATP production rate was observed after endurance training with the substrate combinations pyruvate+palmitoyl-L-carnitine+L-glutamate+malate (P < 0.01), L-glutamate (P < 0.001), pyruvate+malate (P < 0.05) and palmitoyl-L-carnitine+malate (P < 0.01). The largest increase was obtained with L-glutamate (170%). Significant correlations were observed between the percent increase in citrate synthase activity and those of mitochondrial ATP production rates. It was concluded that the increased mitochondrial ATP production rate of aged human skeletal muscle with training seems mainly to occur through an increased mitochondrial content, and in a way similar to those observed in young men.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1995

Effects of training on performance in competitive swimming.

The relationships between the mean intensity of a training season, training volume and frequency, and the variations in performance were studied in a group of 18 elite swimmers. Additionally, differences between the swimmers who improved their personal record of the previous year during the follow-up training season (GIR, n = 8) and those who did not (GNI, n = 10) were investigated. The improvement in performance during the follow-up season was significantly correlated with the mean intensity of the training season (r = 0.69, p < 0.01), but not with training volume or frequency. The performance improvement during the follow-up season was negatively related to the initial performance level (r = 0.90, p < 0.01). The decline in performance during detraining from the previous year was less for the GIR than for the GNI (6.21 +/- 2.30% vs. 9.79 +/- 2.18%, p < 0.01). The present findings suggest that training intensity is the key factor in performance improvement in a group of elite swimmers. Factors such as previous detraining and initial performance level could jeopardize success in spite of a good adaptation to training.

Adaptation, Physiological↗