Jean-Marc Lavoie

Applied Physiology of Swimming

SummaryScientific research in swimming over the past 10 to 15 years has been oriented toward multiple aspects that relate to applied and basic physiology, metabolism, biochemistry, and endocrinology. This review considers recent findings on: 1) specific physical characteristics of swimmers; 2) the energetics of swimming; 3) the evaluation of aerobic fitness in swimming; and 4) some metabolic and hormonal aspects related to swimmers.Firstly, the age of finalists in Olympic swimming is not much different from that of the participants from other sports. They are taller and heavier than a reference population of the same age. The height bias in swimming may be the reason for lack of success from some Asian and African countries. Experimental data point toward greater leanness, particularly in female swimmers, than was seen 10 years ago. Overall, female swimmers present a range of 14 to 19% body fat whereas males are much lower (5 to 10%).Secondly, the relationship between O2 uptake and crawl swimming velocity (at training and competitive speeds) is thought to be linear. The energy cost varies between strokes with a dichotomy between the 2 symmetrical and the 2 asymmetrical strokes. Energy expenditure in swimming is represented by the sum of the cost of translational motion (drag) and maintenance of horizontal motion (gravity). The cost of the latter decreases as speed increases. Examination of the question of size-associated effects on the cost of swimming using Huxley’s allometric equation (Ŷ = axb) shows an almost direct relationship with passive drag. Expressing energy cost in litres of O2/m/kg is proposed as a better index of technical swimming ability than the traditional expression of V̇O2/distance in L/km.Thirdly, maximal direct conventional techniques used to evaluate maximal oxygen consumption (V̇V̇O2 max) in swimming include free swimming, tethered swimming, and flume swimming. Despite the individual pecularities of each method, with similar experimental conditions similar results for V̇O2 max will be found. Free swimming (unimpeded) using the backward extrapolation method will, however, lead to reliable and valid results obtained in a condition that is closer to the competitive situation than with a direct test. A maximal indirect field-test has been recently made available. This test can predict V̇O2 max with an acceptable accuracy (r = 0.877), and provides a mean to evaluate the functional maximal aerobic power in swimming which corresponds to the maximal aerobic swimming velocity.Finally, although general principles of metabolic and endocrine aspects of exercise also apply to swimming, researchers have given a new but growing attention to specific aspects of metabolic and hormonal responses in swimmers. Metabolic studies in swimming point to a certain degree of disparity between swim training and the competitive events as far as substrate utilisation is concerned. Lactate response during swimming has also been used extensively to estimate the kinetics of energy production at submaximal and maximal exercise levels. Reports on endocrine responses specifically related to swimmers have mainly been directed toward the study of the menstrual cycle. Contrary to female gymnasts, the age ofmenarche of girl swimmers has been shown to be somewhat delayed or not delayed at all, although a later age at menarche has been recently observed for the more competitive swimmers. The incidence of athletic amenorrhoea also appears to be higher in runners and ballet dancers than in swimmers.

EFFECT OF VOLUNTARY EXERCISE ON H2O2 RELEASE BY SUBSARCOLEMMAL, AND INTERMYOFIBRILLAR MITOCHONDRIA

Previous data have demonstrated that, to handle the oxidative stress encountered with training at high intensity, skeletal muscle relies on an increase in mitochondrial biogenesis, a reduced H(2)O(2) production, and an enhancement of antioxidant enzymes. In the present study, we evaluated the influence of voluntary running on mitochondrial O(2) consumption and H(2)O(2) production by intermyofibrillar mitochondria (IFM) and subsarcolemmal mitochondria (SSM) isolated from oxidative muscles in conjunction with the determination of antioxidant capacities. When mitochondria are incubated with succinate as substrate, both maximal (state 3) and resting (state 4) O(2) consumption were significantly lower in SSM than in IFM populations. Mitochondrial H(2)O(2) release per unit of O(2) consumed was 2-fold higher in SSM than in IFM. Inhibition of H(2)O(2) formation by rotenone suggests that complex I of the electron transport chain is likely the major physiological H(2)O(2)-generating system. In Lou/C rats (an inbred strain of rats of Wistar origin), neither O(2) consumption nor H(2)O(2) release by IFM and SSM were affected by long-term, voluntary wheel training. In contrast, glutathione peroxidase and catalase activity were significantly increased despite no change in oxidative capacities with long-term, voluntary exercise. Furthermore, chronic exercise enhanced heat shock protein 72 accumulation within skeletal muscle. It is concluded that the antioxidant status of muscle can be significantly improved by prolonged wheel exercise without necessitating an increase in mitochondrial oxidative capacities.

Metabolically healthy but obese individuals: relationship with hepatic enzymes

The purpose of this study was to investigate the level of plasma hepatic enzymes in obese women displaying the metabolically healthy but obese (MHO) phenotype. We studied 104 obese, sedentary, postmenopausal women. Subjects were classified as MHO or at risk based on insulin sensitivity as assessed with the oral glucose tolerance test-derived Matsuda index. Subjects were divided into quartiles according to insulin sensitivity values. Subjects in the upper quartile were categorized as MHO, whereas subjects in the lower 3 quartiles represented at-risk subjects. Outcome measures were hepatic enzymes (aspartate aminotransferase [AST], alanine aminotransferase [ALT], alkaline phosphatase, and gamma-glutamyltransferase [GGT]], high-density lipoprotein cholesterol, triglycerides, triglycerides to high-density lipoprotein cholesterol ratio, apolipoprotein B, fatty liver index, body composition (dual-energy x-ray absorptiometry), and visceral adipose tissue (computed tomography). The MHO individuals had significantly lower concentrations of ALT, AST, and GGT as well as a lower fatty liver index compared with at-risk subjects (P < .05). In addition, lean body mass index and visceral adipose tissue were significantly lower in MHO individuals (P < .05). Moreover, stepwise regression analysis showed that ALT explained 17.9% of the variation in insulin sensitivity in our cohort, which accounted for the greatest source of unique variance. Results of the present study indicate that postmenopausal women displaying the MHO phenotype present favorable levels of ALT, AST, and GGT. Lower concentrations of hepatic enzymes, in particular, lower circulating ALT levels, in MHO individuals may reflect lower hepatic insulin resistance and lower liver fat content; and this could be involved, at least in part, in the protective profile of MHO individuals.

Resistance Training Does Not Contribute to Improving the Metabolic Profile after a 6-Month Weight Loss Program in Overweight and Obese Postmenopausal Women

CONTEXT Limited data are available regarding the impact of caloric restriction (CR) in combination with resistance training (RT) on the metabolic profile of postmenopausal women. OBJECTIVE The objective of the study was to determine whether RT adds to CR in improving body composition and the metabolic profile. DESIGN AND SETTING This was a 6-month, randomized, clinical trial. PATIENTS Patients included 107 postmenopausal women (body mass index >27 kg/m(2)). INTERVENTION The intervention was a 6-month CR alone or in combination with a RT program. MAIN OUTCOME MEASURES Fat mass (FM), lean body mass (LBM), abdominal sc fat and visceral fat, fasting lipids, insulin sensitivity, resting blood pressure, and inflammation markers were measured. RESULTS Both groups were similar at baseline and significantly decreased body weight, body mass index, FM, percent FM, abdominal sc fat, and visceral fat after the study (P < 0.001), with greater losses of percent FM and trunk FM in the CR + RT group (P < 0.05). LMB significantly decreased in the CR (-0.9 +/- 2.4 kg) and the CR+RT (-0.4 +/- 2.2 kg) groups (P < 0.005), with no difference between them. Both groups significantly improved plasma triglycerides, fasting insulin level, glucose disposal, and markers of the inflammation profile after weight loss (P < 0.05), with no difference between groups. No improvements were observed for the other variables of interest in both groups. CONCLUSIONS CR+RT was associated with greater losses in percent FM and trunk FM compared with CR alone. However, CR+RT was not associated with additional improvements in the metabolic profile compared with CR alone.

Analysis of determinants of swimming economy in front crawl

SummaryThe 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<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< 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.

The effect of the menopausal transition on body composition and cardiometabolic risk factors: a Montreal-Ottawa New Emerging Team group study

Objective Cardiovascular disease is the first cause of mortality in women in North America. The risk of cardiovascular disease increases sharply after middle age in women, especially after menopause. The aim was to investigate changes in body composition and cardiometabolic profile throughout the menopausal transition. Methods This was a 5-year observational, longitudinal study on the menopausal transition. The study included 102 premenopausal women at baseline (age, 49.9 ± 1.9 y; body mass index, 23.3 ± 2.2 kg/m2). Outcome measures include menopause status, body composition by dual-energy x-ray absorptiometry (total fat mass [FM], trunk FM, and total fat-free mass), waist circumference, visceral and abdominal subcutaneous fat, fasting glucose and insulin levels, homeostasis model assessment of insulin resistance, plasma lipid levels (triglycerides, total cholesterol, and high- and low-density lipoprotein cholesterol), and resting blood pressure. Results Repeated-measure analyses revealed significant increases for FM, percentage FM, trunk FM, visceral fat, plasma fasting glucose, and high-density lipoprotein cholesterol (0.05 > P < 0.01) and a significant decrease for plasma glucose levels after follow-up. Those who were in perimenopause or postmenopause by year 3 of the study showed a significant increase in visceral fat (P < 0.01) compared with baseline. Despite some significant changes in the metabolic profile among the menopause statuses, the women did not show any cardiometabolic deterioration by the end of the study. Conclusions Our results suggest that changes in body composition and fat distribution can occur in nonobese women as they go through the menopausal transition. However, these changes were not accompanied by cardiometabolic deteriorations in the present study.

Time course of the development of non-alcoholic hepatic steatosis in response to high-fat diet-induced obesity in rats.

The aim of the study was to characterize the time course of the development of high-fat diet-induced hepatic steatosis and its relation to body fat accretion and changes in plasma lipid profile. Female Sprague-Dawley rats were high-fat fed (HF; 42 %, kJ) for 1, 2, 4, 6, 12 and 16 weeks and compared to standard fed rats (SD). Data obtained from HF rats were further analysed by classifying the animals into obesity-prone and obesity-resistant. In HF rats, liver lipid content increased rapidly by approximately 200 % during the first 2 weeks, decreased almost to baseline levels between weeks 2 and 6, and re-increased by 17 % between weeks 6 and 16 (P<0.05). Body weight, body fat accretion, plasma leptin, NEFA and glycerol concentrations were higher in HF than in SD rats (P<0.05). These higher values were established in 2 weeks and the differences between the groups did not further enlarge from weeks 2 to 16. Obesity-prone rats depicted higher body weight and body fat accretion than obesity-resistant and SD rats. Surprisingly, however, liver lipid content was the same in obesity-prone as in obesity-resistant rats as they were both higher than in SD rats (weeks 2 and 16; P<0.05). Our data support the hypothesis that the liver acts as a systemic buffer, largely increasing its lipid content in the early stage of high-fat feeding. Our results also suggest that the development of non-alcoholic hepatic steatosis is more linked to dietary fat ingestion than to body weight gain.

Effects of ovariectomy on PPAR alpha, SREBP-1c, and SCD-1 gene expression in the rat liver.

Objective:To investigate whether estrogen deficiency modifies the expression of important genes involved in hepatic lipid regulation, PPAR&agr;, SREBP-1c, and SCD-1, in association with fat accumulation in the liver of ovariectomized rats. Design:Thirty female Sprague-Dawley rats were divided into three groups: sham-operated (n = 12), ovariectomized (n = 12), and ovariectomized with 17&bgr;-estradiol replacement (n = 6). All animals were killed 8 weeks after surgery. In addition to liver triacylglycerol determination, transcripts levels and protein content of peroxisome proliferator-activated receptor &agr;, liver sterol regulatory element-binding protein 1c, and stearoyl coenzyme Adesaturase 1 were quantified by quantitative real-time polymerase chain reaction and Western blot, respectively. Results:As expected, liver triacylglycerol levels were higher (51%; 21.9 ± 2.6 vs 14.5 ± 1.2 mg/g; P < 0.01) in ovariectomized compared with sham-operated rats. Peroxisome proliferator-activated receptor &agr; mRNA levels were 66% lower (P < 0.01), whereas sterol regulatory element-binding protein 1 and stearoyl coenzyme A desaturase 1 transcript levels were 80% and 41% higher (P < 0.05), respectively, after estrogen removal. Our data on gene expression obtained with quantitative real-time polymerase chain reaction for peroxisome proliferator-activated receptor &agr; and sterol regulatory element-binding protein 1c were confirmed by Western blots. All the effects of ovariectomy were prevented by 17&bgr;-estradiol replacement, indicating a role for estrogens in the prevention of hepatic fat accumulation. Conclusions:Our results suggest that a reduction in lipid oxidation and an increase in lipogenesis are defective mechanisms leading to lipid accumulation in the liver of ovariectomized rats. We conclude that estrogen deficiency induced by ovariectomy changes the expression of genes that favor the development of a steatotic phenotype.

\(\dot VO_2 \) peak during free swimming using the backward extrapolation of the O2 recovery curve

SummaryThe purpose of this study was to evaluate the accuracy and feasibility of estimating oxygen consumption (