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.

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.

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.

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.

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.

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.

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.

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.