Biomedical subjects

J C Chatard

Publications and source records attributed to J C Chatard.

43 records · Page 3Linked to original sources

PubMed1990

Analysis of determinants of swimming economy in front crawl.

The purpose of this study was to investigate the relationship between swimming economy, energy cost to move the body per unit distance (CS) at a given velocity (v) and the potential determinants, i.e. performance level, body size, swimming technique and v. A total of 101 males were studied. Three performance levels (A, B, C) were determined, ranging from the slower (A) to the faster times (B, C). At level C and at 1.1 m.s-1, CS 1.1, was reduced by 55% and 25% when compared with levels A and B and when calculated per unit of surface area (SA) and unit of hydrostatic lift (HL). For the whole group of swimmers, CS 1.1 = 21.88 SA-2.15 HL + 5.9 (r = 0.56, P less than 0.01). Among the 101 swimmers, three other groups were selected to evaluate specifically the influence of arm length and swimming technique on CS, i.e. arm or leg swimmers and sprinters versus long-distance swimmers, CS was significantly (P less than 0.05) lower for long-arm swimmers, arm and long-distance swimmers than for short-arm, leg and sprint swimmers by 12%, SD 3.3%, 15%, SD 3.8% and 16.5%, SD 3%, respectively. For all groups, CS increased with v on average by 10% every 0.1 m.s-1. It is concluded that technical ability cannot be interpreted directly from CS. Performance levels, body size, swimming technique and v at which the measurements are obtained must be also taken into account.

Adolescent↗

PubMed1990

Passive drag is still a good evaluator of swimming aptitude.

The passive drag (Dp) of 218 competitive swimmers was studied and related to their performance level. To study this relationship, specific attention was given to anthropometric and joint laxity (JL) variations. The Dp was measured at 1.40 m.s-1, using a mechanical winch and a strain gauge with a load cell connected to a strain bridge. Swimmers were towed in a prone position holding their breath after a maximal inspiration. Buoyancy was evaluated by the hydrostatic lift (HL), i.e., the maximal weight just necessary to maintain the swimmer in a balanced position under the water after a maximal inspiration. The JL was assessed by a standard scoring system. The Dp was related mainly to the surface area (SA) (r = 0.73 and 0.53; P less than 0.01, for males and females, respectively). For a given SA, Dp was inversely related to the performance level. The JL explained 7% of the variability of Dp. On average, Dp measured after a maximal expiration, increases of about 22% SD 3% (P less than 0.01). This increase was related to individual vital capacities (r = 0.86, P less than 0.01). As Dp was mainly related to SA and HL, it is suggested that the body exerts a large pressure effect on the water. The contribution to performance might be related to the gliding phase of swimming.

Adolescent↗

PubMed1990

Swimming skill and stroking characteristics of front crawl swimmers.

The performance over a 368-meter swim, VO2max, stroke pulling pattern and anthropometric data of nine male competitive freestylers were studied to identify aspects of swimming techniques which allow a swimmer to be "more skilled" than another. Performance was mainly related to VOmax, r = 0.80, the incorporation of the hydrostatic lift increased the correlation coefficient to 0.87 at the second stepwise regression. The real performance was compared to the theoretical performance obtained from the results of the stepwise regression. The group of four swimmers whose real performance was higher than that calculated by the regression equation was considered "skilled", when compared to the other group ("less skilled"). "Skilled" swimmers were characterized by a higher stroke frequency and superposition of both arm actions, a shorter stroke length, downsweep phase and longer upsweep phase. Those two phases were linked together, r = -0.88, p less than 0.01, but not related to stroke rate. Entry phase and depth of stroke pattern were related to hydrostatic lift, r = -0.80 and 0.77, respectively, p less than 0.01. However, there was no relationship between stroke length and anthropometric data.

Adult↗

PubMed1990

The contribution of passive drag as a determinant of swimming performance.

The purpose of the present investigation was to evaluate the contribution of passive drag (Dp) to the prediction of a 400-m swim. A second aim was to evaluate the relation between Dp and some anthropometric factors. In a first experiment, 84 swimmers (both sexes) had their Dp (at 1.4 m.s-1) and VO2max measured in water and put into relation with the performance time of a 400-m swim. Performance times were mainly related to VO2max (r = 0.70 and 0.72, p less than 0.01, for male and female swimmers, respectively). Inclusion of Dp as a second variable improved significantly (p less than 0.01) the accuracy of the regression up to 0.75 and 0.78. Passive drag was also significantly (p less than 0.01) related to height (r = 0.80 and 0.60, p less than 0.01, for male and female swimmers, respectively), weight (r = 0.78 and 0.54, p less than 0.01, for males and females, respectively), and body surface area (r = 0.80 and 0.58, p less than 0.01, for males and females, respectively). In a second group of 7 male swimmers, it was found that Dp values were increased on average by 34% (p less than 0.01) when measured after a maximal expiration as compared to measurements after a maximal inspiration. In a third group of swimmers (n = 41) for which generalized joint laxity was measured, it was found that this variable contributes significantly to the Dp variability. The present results show that Dp can be considered as contributing significantly to prediction of performance in swimming.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1989

Relationship between the 4 mmol running velocity, the time-distance relationship and the Léger-Boucher's test.

The relationship between distance and best time is roughly linear for distances between 1500 and 5000 m. The slope of this relationship has the dimension of a velocity (Vlim) which can be sustained during a long time. The individual time-distance relationships and the resulting Vlim have been studied in 32 subjects practicing different athletic activities by measuring exhaustion time for 2 to 4 constant-velocity running exercises performed to exhaustion. The velocity corresponding to 4 mmol.l-1 of blood lactate (V4 mmol) has been compared with Vlim. As maximal oxygen uptake is a major factor determining V4 mmol, Vlim and V4 mmol have also been correlated with the result of a field test which is assumed to measure maximal aerobic power (Léger-Boucher's test). This test consists in running until exhaustion at a velocity which increases every two minutes. The higher the velocity at exhaustion (Vléger) is, the higher the maximal oxygen uptake is assumed. Both Vlim and Vléger were very well correlated with V4 mmol (r greater than 0.90) and the average value of Vlim was almost equal to the average value of V4 mmol (13.89 vs 13.71 km.h-1). However, it was not possible to estimate V4 mmol accurately from the values of Vlim or Vléger because the standard errors of estimates were too large.

Exercise↗

PubMed1986

Effects of endurance training on capillary supply of human skeletal muscle on two age groups (20 and 60 years).

Two groups of human subjects were submitted to a 20-week endurance training program (1 h a day, 4 days a week, 70-80% max VO2). The first group (G20) consisted of eight 22 +/- 3 years male students, the second group (G60) was composed of seven still very physically active elderly male subjects (62 +/- 4 years). Training significantly increased max VO2 by 15% in G20 and 7% in G60. Muscle samples taken from the vastus lateralis muscle before and after training were histochemically stained for fibre-typing (myofibrillar ATPase), capillary supply and fibre area measurements (amylase PAS and NADH-TR). Fibre-type distribution was unchanged with training. Capillary density (cap X mm-2) increased significantly in both groups from 316 +/- 42 to 396 +/- 73 in G20 and from 308 +/- 48 to 409 +/- 55 in G60. This enhancement of capillary supply was linked to the proliferation of capillaries in G20 where the number of capillaries in contact with ST and FTa fibres (CC) significantly increased from 4.6 to 5.9 and from 4.8 to 6.1 respectively. No significant changes in fibre areas were found in G20. On the contrary, G60 did not show any significant sign of capillary growth (CC unchanged) whereas fibre areas significantly decreased in ST (6,410 to 5,520 micron 2) and FTa fibres (5,830 to 5,090 micron 2). A methodological evaluation of fibre-area measurement was described, with confirmation of the data. It was concluded that this study may illustrate the trainability of skeletal muscle of elderly men in a possibly different way to that seen in a younger age group.

Adult↗

PubMed1984

[Maximal effort, maximal heart rate and serum lactic acid in exercise electrocardiography. A comparative study].

In exercise stress testing the quantification of effort on which the value and significance of the test depend is based on two simple and practical criteria: theoretical maximal heart rate for age (MHR) and serum lactic acid levels 3 minutes after exercise. Usually only MHR is used, 85% of MHR being the common cut-off point between "interpretable" maximal or "inframaximal" effort and useless effort. Our study was based on 1 000 exercise stress tests performed over a two year period with the same protocol and equipment. Initially, we determined our values of MHR and serum lactic acid in undoubted maximal effort stress tests, as shown by a levelling out of the heart rate during the last load increments, the last stage of exercise being sustained for at least 1.5 minute. The application of both criteria to all the investigations showed significant differences in the evaluation of the exercise obtained when the maximal measured heart rate was between 85 and 95% of MHR. This was also true, to a lesser extent, in patients over 60 years of age or under 30 years of age with maximal measured heart rate of 85% or less than MHR. A discussion of the theoretical basis of the two criteria helps explain this divergence, attributing it to the inaccuracy and unreliability of the MHR. The only obstacle to the use of serum lactate as the preferential indicator of maximal effort is the need for laboratory facilities and the delay in obtaining the result.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗