Fabienne Mougin

Influence of exercise duration on serum insulin-like growth factor and its binding proteins in athletes

Abstract The changes in circulating concentrations of insulin-like growth factors during exercise have to date remained incomplete in their documentation. Therefore, we examined in 25 healthy athletes the effects of three different durations of three types of exercise – incremental ergometer cycling exercise (ICE), long-distance Nordic ski race (NSR) and a treadmill-simulated soccer game (TSG) lasting 20 min, 3 h, and 2 × 45 min separated by a 15-min half-time rest respectively, on plasma concentrations of growth hormone ([GH]), insulin-like growth factor-1 ([IGF-I]) and its binding proteins 1 and 3 ([IGFBP-1], [IGFBP-3]). Compared to baseline, serum [GH] increased by 15.2-fold after ICE (P < 0.001), 2.9-fold after NSR (P < 0.01) and 4.6-fold after TSG. Serum [IGF-I] rose by 11.9% after ICE (P < 0.001), while it decreased by −14.6% after NSR (P < 0.001) and was unchanged after TSG. Serum [IGFBP-1] was slightly increased (1.7-fold) after ICE (P < 0.01), but increased markedly (11.8-fold) after NSR (P < 0.001) and by 6.3-fold after the second session of TSG (P < 0.01) (it remained unchanged at the end of the first period of TSG, i.e. after 45-min exercise). The [IGFBP-3] increased by 14.7% after ICE (P < 0.001) and by 6% after TSG (P < 0.05) while it did not change after NSR. From our results it would appear that [IGFBP-1] increase to bind free IGF and hinder their insulin-like action during long-term exercise (lasting beyond 45 min). It is suggested that IGFBP-1 might thus contribute both to preventing hypoglycaemic action of IGF and to facilitating glucose uptake by muscle cells when muscle glycogen stores become deplete.

Effects of sleep disturbances on subsequent physical performance.

SummaryThe purpose of the study was to compare the cardiovascular, respiratory and metabolic responses to exercise of highly endurance trained subjects after 3 different nights i.e. a baseline night, a partial sleep deprivation of 3 h in the middle of the night and a 0.25-mg triazolam-induced sleep. Sleep-waking chronobiology and endurance performance capacity were taken into account in the choice of the subjects. Seven subjects exercised on a cycle ergometer for a 10-min warmup, then for 20 min at a steady exercise intensity (equal to the intensity corresponding to 75% of the predetermined maximal oxygen consumption) followed by an increased intensity until exhaustion. The night with 3 h sleep loss was accompanied by a greater number of periods of wakefulness (P<0.01) and fewer periods of stage 2 sleep (P<0.05) compared with the results recorded during the baseline night. Triazolam-induced sleep led to an increase in stage 2 sleep (P<0.05), a decrease in wakefulness (P<0.05) and in stage 3 sleep (P<0.05) After partial sleep deprivation, there were statistically significant increases in heart rate (P<0.05) and ventilation (P<0.05) at submaximal exercise compared with results obtained after the baseline night. Both variables were also significantly enhanced at maximal exercise, while the peak oxygen consumption (VO2) dropped (P<0.05) even though the maximal sustained exercise intensity was not different. Lactate accumulation was altered by sleep loss, undergoing an upward drift from the 9th min of steady power output [4.92 (SEM 0.44) mmol·1−1 vs control (CT) 3.91 (SEM 0.27) mmol·1−1, P<0.05] until maximal effort [10.92 (SEM 0.83) mmol·1−1 vs CT 9.26 (SEM 0.79) mmol·1−1, P<0.05]. After triazolam-induced sleep, heart rate, ventilation, (VO2) and blood lactates were not significantly different during steady power output from the values observed after the baseline night. However the maximal sustained exercise intensity was greater [380 (SEM 13.1) W vs CT 361.4 (SEM 13) W, P<0.01], which led to an increase in ventilation (P<0.01) without any change in heart rate, (VO2) or lactate concentration. These results suggested that partial sleep loss may have contributed to the change in athletic performance and that triazolam did not impair the physiological responses to exercise during the following afternoon.

Physical Training Decreases Total Plasma Homocysteine and Cysteine in Middle-Aged Subjects

Aims: The aim of this study was to evaluate whether endurance exercise in middle-aged men induces changes in plasma total homocysteine (tHcy) and total cysteine (tCys), and whether these changes depend on the diet especially on vitamin B6, folic acid and vitamin B12 intakes. Methods: Twelve trained subjects (52.33 ± 2.4 years) and twelve untrained subjects (56.23 ± 0.9 years) volunteered for the present study. tHcy and tCys were measured with high-pressure liquid chromatography at rest in both groups and during an incremental exercise performed on a cycle ergometer until exhaustion in the trained subjects. Results: At baseline homocysteinemia and cysteinemia were lower in trained subjects (7.48 ± 0.4 and 183.45 ± 13.6 µmol/l) compared with untrained subjects (9.79 ± 0.4 µmol/l, p < 0.001; 229.01 ±14.7 µmol/l, p < 0.05, respectively). Incremental exercise also induced a decrease in tHcy and tCys concentrations. Moreover, tHcy concentration was negatively related to the folic acid and B12 intakes in untrained (r = –0.589, p < 0.05; r = –0.580, p < 0.05, respectively) as well as in trained groups (r = –0.709, p < 0.01; r = –0.731, p < 0.01, respectively) whereas no correlation between tCys and vitamin in the diet was observed. Conclusion: This study demonstrates that the combined effects of a chronic physical exercise and a high folate and vitamin B12 intake could be responsible for the reduction of plasma tHcy and tCys concentrations that might be a key for the prevention of many diseases.

Hormonal responses to exercise after partial sleep deprivation and after a hypnotic drug-induced sleep

The aim of this study was to determine the hormonal responses, which are dependent on the sleep-wake cycle, to strenuous physical exercise. Exercise was performed after different nocturnal regimens: (i) a baseline night preceded by a habituation night; (ii) two nights of partial sleep deprivation caused by a delayed bedtime or by an early awakening; and (iii) two nights of sleep after administration of either a hypnotic compound (10 mg zolpidem) or a placebo. Eight well-trained male endurance athletes with a maximal oxygen uptake of 63.5±3.8 ml kg-1 min-1 (mean value ±s X ) were selected on the basis of their sleeping habits and their physical training. Polygraphic recordings of EEG showed that both nights with partial sleep loss led to a decrease (P < 0.01) in stage 2 and rapid eye movement sleep. A delayed bedtime also led to a decrease (P < 0.05) in stage 1 sleep. Zolpidem had no effect on the different stages of sleep. During the afternoon after an experimental night, exercise was performed on a cycle ergometer. After a 10-min warm-up, the participants performed 30 min steady-state cycling at 75%O2max followed by a progressively increased workload until exhaustion. The recovery period lasted 30 min. Plasma growth hormone, prolactin, cortisol, catecholamine and lactate concentrations were measured at rest, during exercise and after recovery. The concentration of plasma growth hormone and catecholamine were not affected by partial sleep deprivation, whereas that of plasma prolactin was higher (P < 0.05) during the trial after an early awakening. Plasma cortisol was lower (P < 0.05) during recovery after both sleep deprivation conditions. Blood lactate was higher (P < 0.05) during submaximal exercise performed after both a delayed bedtime and an early awakening. Zolpidem-induced sleep did not affect the hormonal and metabolic responses to subsequent exercise. Our results demonstrate only minor alterations in the hormonal responses to exercise after partial sleep deprivation.

Two-Dimensional Strain and Twist by Vector Velocity Imaging in Adolescents With Severe Obesity

The prevalence of severe obesity is increasing worldwide in adolescents. Whether it is associated with functional myocardial abnormalities remains largely unknown, potentially because of its frequent association with other cardiovascular risk factors and also use of insensitive techniques to detect subclinical changes in myocardial function. We used 2D vector velocity imaging (VVI) to investigate early changes in left ventricular (LV) myocardial function in youths with isolated severe obesity. Thirty‐seven asymptomatic severely obese adolescents free of diabetes and hypertension, and 24 lean controls were enrolled. LV longitudinal, basal, and apical circumferential strain, strain rate (SR), rotations, and LV twist were measured. Obese adolescents had greater LV mass and reduced systolic and early diastolic tissue Doppler imaging (TDI) velocities than lean counterparts. L strain (−24%) and systolic and early diastolic SR were also diminished in the obese, whereas no intergroup differences existed for the circumferential deformation indexes. LV twist was more pronounced in the obese (+1.7°, P < 0.01) on account of greater apical rotation only (4.1 ± 0.9 vs. 5.2 ± 1.2°, P < 0.01), potentially compensating for the loss in longitudinal function. Systolic—diastolic coupling, an important component of early filling and diastolic function, was maintained with severe obesity. No intergroup differences were reported regarding time to peak values for all VVI indexes highlighting that dynamics of strain and twist/untwist along the cardiac cycle was preserved with severe obesity. Isolated severe obesity in adolescents, at a preclinical stage, is associated with changes in myocardial deformation and torsional mechanics that could be in part related to alterations in relaxation and contractility properties of subendocardial fibers.

Physical activity in patients with rheumatoid arthritis.

INTRODUCTION Rheumatoid arthritis (RA) is the most common chronic inflammatory joint disease and is associated with an excess risk of cardiovascular disease. For the general population, the World Health Organization has issued detailed recommendations on the type of physical activity appropriate for decreasing the cardiovascular risk. The objective of this work is to review available data on the effects of physical activity in patients with RA. RESULTS RA is responsible for a marked decrease in physical activity. Physical activity significantly diminishes both the cardiovascular risk and the DAS 28. Vascular benefits from physical activity include improved endothelial function and slowing of the atherosclerotic process. Physical activity also has favorable effects on bone, slowing radiographic disease progression in small joints and increasing bone mineral density at the femoral neck, although these effects are not statistically significant. Finally, engaging in physical activity increases self-esteem, alleviates symptoms of depression, improves sleep quality, and decreases pain perception. Aerobic exercise is the most commonly advocated type of physical activity. Most interventions were of short duration (4 weeks) and involved aerobic activity (running or cycling) for 60minutes a day 5 days a week. Resistance training has been shown to decrease systemic inflammation and increase muscle strength. The main obstacles to physical activity in patients with RA are related to both the patients, who lack both motivation and knowledge, and the rheumatologists, who also lack knowledge and place insufficient emphasis on promoting physical activity. CONCLUSION Physical activity provides many benefits in patients with RA and should be widely performed. Promoting physical activity should be among the objectives of therapeutic patient education for RA.

Evaluation of cardiorespiratory fitness using three field tests in obese adolescents: Validity, sensitivity and prediction of peak V ˙ O 2

OBJECTIVES Evaluation of cardiorespiratory fitness in obese adolescents is necessary to develop personalised retraining programmes. We aimed to measure cardiorespiratory fitness using 3 field tests, and to evaluate their validity and sensitivity compared to values obtained by laboratory tests. DESIGN Longitudinal interventional study in obese adolescents admitted to a rehabilitation centre for a 9-month programme of obesity management. METHODS A 12-min walk/run test, an adapted 20 m shuttle walk-run test (starting speed 4 km h(-1), increments of 0.5 km h(-1)min(-1)) and a 4-level submaximal cycle ergometer test were performed to estimate respectively distance covered in 12 min, maximum speed and maximal aerobic power. RESULTS Thirty adolescents aged 14.2 ± 1.6 years were included. After 9 months intervention, we observed a significant reduction in body mass index, and an increase in peak VO2 and field test results. We observed significant correlations between pre- and post-intervention values of peak VO2 and distance covered in 12 min (r=0.70 pre; r=0.82 post), maximum speed (r=0.80 pre; r=0.83 post) and maximal aerobic power (r=0.71 pre; r=0.84 post). Multiple linear regression made it possible to estimate peak VO2 based on results from the 3 field tests using prediction equations specific to a population of obese adolescents. CONCLUSIONS These field tests, including the adapted 20 m shuttle walk-run test, adequately assess cardiorespiratory fitness in obese adolescents, and are sensitive to changes over time. Predictive equations including BMI are useful in clinical practice to predict peak VO2 in these patients.

Effects of an in-patient treatment program based on regular exercise and a balanced diet on high molecular weight adiponectin, resistin levels, and insulin resistance in adolescents with severe obesity.

Adiponectin, the most abundant hormone produced by adipose tissue, circulates in 3 isoforms, including high molecular weight (HMW) adiponectin. The latter has been suggested to be a better predictor of metabolic disturbances and insulin resistance associated with obesity. This study investigated changes in total and HMW adiponectin, resistin, and homeostasis model assessment (HOMA) during a 9-month in-patient treatment program based on physical exercise and a balanced diet in 32 severely obese adolescents. Total and HMW adiponectin, resistin, and HOMA were measured at baseline (month 0) and during the program (months 3, 6, 9). In addition, a control group of 15 teenagers served as a reference for the baseline assessments. At baseline, HMW adiponectin was more markedly decreased in obese adolescents than total adiponectin, and both were lower than in controls. Conversely, resistin and HOMA were higher in obese adolescents. During the program, there was a significant change in body composition and improved insulin sensitivity among obese teenagers. In addition, HMW adiponectin and the ratio of HMW-to-total adiponectin increased throughout the study, whereas total adiponectin only increased up until the sixth month. On the contrary, resistin did not show any significant change. In obese adolescents, a long-term combination of aerobic exercise and a balanced diet, inducing change in body composition and improved insulin sensitivity, markedly increased HMW adiponectin compared with total adiponectin, without any change in resistin concentrations. Our results thus suggest that the determination of HMW adiponectin could be more useful than measurement of total adiponectin in clinical settings.

Combined intervention of dietary soybean proteins and swim training : effects on bone metabolism in ovariectomized rats

Soybean proteins, a rich source of isoflavones, taken immediately after an ovariectomy prevent bone loss in rats. Exercise-induced stimuli are essential for bone growth. Few studies exist about the combined effects of swim training and soybean protein supplementation on bone metabolism. So, the purpose of this study was to investigate, in 48 female Sprague-Dawley rats (12 weeks old) the effects of an 8-week swim-training regimen (1 h/day, 5 days/week) and dietary soybean proteins (200 g/kg diet) on bone metabolism. Rats were randomly assigned to four groups: (1) ovariectomized fed with a semisynthetic control diet; (2) ovariectomized fed with a soybean protein-enriched semisynthetic diet; (3) ovariectomized trained to exercise and fed with control diet; (4) ovariectomized trained to exercise and fed with a soybean protein diet. Following the treatment period, body weight gain was identical in the four groups. Soybean protein supplementation increased bone calcium content, and reduced plasma osteocalcin values, without significant modification of calcium balance and net calcium absorption. Swim training enhanced plasma and bone calcium content and calcium balance and net calcium absorption. It did not modify either plasma osteocalcin values or urinary deoxypyridinoline excretion. Both exercise and soybean protein intake increased plasma on bone calcium without modifying net calcium absorption or bone markers. In conclusion, we demonstrated, in ovariectomized rats, that swimming exercise and dietary supplementation with soy proteins do not have synergistic effects on calcium metabolism and bone markers.

Ventilatory Thresholds Determined from HRV: Comparison of 2 Methods in Obese Adolescents

The development of personalised training programmes is crucial in the management of obesity. We evaluated the ability of 2 heart rate variability analyses to determine ventilatory thresholds (VT) in obese adolescents. 20 adolescents (mean age 14.3±1.6 years and body mass index z-score 4.2±0.1) performed an incremental test to exhaustion before and after a 9-month multidisciplinary management programme. The first (VT1) and second (VT2) ventilatory thresholds were identified by the reference method (gas exchanges). We recorded RR intervals to estimate VT1 and VT2 from heart rate variability using time-domain analysis and time-varying spectral-domain analysis. The coefficient correlations between thresholds were higher with spectral-domain analysis compared to time-domain analysis: Heart rate at VT1: r=0.91 vs. =0.66 and VT2: r=0.91 vs. =0.66; power at VT1: r=0.91 vs. =0.74 and VT2: r=0.93 vs. =0.78; spectral-domain vs. time-domain analysis respectively). No systematic bias in heart rate at VT1 and VT2 with standard deviations <6 bpm were found, confirming that spectral-domain analysis could replace the reference method for the detection of ventilatory thresholds. Furthermore, this technique is sensitive to rehabilitation and re-training, which underlines its utility in clinical practice. This inexpensive and non-invasive tool is promising for prescribing physical activity programs in obese adolescents.