Biomedical subjects

J-R Lacour

Publications and source records attributed to J-R Lacour.

9 recordsLinked to original sources

PubMed2006

Heart rate variability, training variation and performance in elite swimmers.

The aim of the present study was to investigate the relationships between heart rate variability (HRV) changes and both training variations and performances in elite swimmers. A secondary purpose was to measure catecholamine urinary excretion in elite swimmers to validate the HRV indices of sympathetic activity during training. Thirteen swimmers (4 females and 9 males) were tested before and after 4 weeks of intense training (IT) and 3 weeks of reduced training (RT). At the end of each period, the swimmers participated in an official competition of their best event. Individual performances were expressed as percentage of the previous season's best performance. Spectral analysis was used to investigate RR interval variability. HRV indices failed to show any significant changes between the study periods (p>0.05). Pre-IT HF was correlated with performance (r=0.45; p=0.05) and HFnu (r=0.59; p<0.05) during RT. On the other hand, once RT was completed, HFnu was correlated positively to performance (r=0.81; p<0.01) and negatively to fatigue (r=- 0.63; p<0.03). Conversely, the indices of sympathetic activity, i.e., LFnu and LF/HF ratio were inversely related to performance (both r=- 0.81; p<0.01); total fatigue score was correlated to the changes in HFnu (r=- 0.63; p<0.03) and in the LF/HF ratio (r=0.58; p<0.05). Changes in the adrenaline/noradrenaline ratio over the follow-up period were related to the changes in the LF/HF ratio (r=0.45; p<0.03). In highly trained swimmers coping well with a training program, including 4 weeks of IT followed by 3 weeks of RT, HRV indices were unaltered. On the other hand, after the 3 weeks of RT, HFnu was positively related to performance and inversely related to the fatigue score. Thus, elevated initial HF levels could be important in the parasympathetic activity increases during taper and, hence, in swimming performance improvement.

Adult↗

PubMed2006

Effects of training on lactate kinetics parameters and their influence on short high-intensity exercise performance.

The purpose of the present study was to relate the training-induced alterations in lactate kinetics parameters to the concomitant changes in time to exhaustion (T(lim)) at a work rate corresponding to maximal oxygen uptake (Pa(peak)). Eight subjects performed before and after training i) an incremental exercise up to exhaustion to determine Pa(peak), ii) a 5-min 90 % Pa(peak) exercise followed by a 90-min passive recovery to determine an individual blood lactate recovery curve fitted to the bi-exponential time function: La(t) = La(0) + A1(1 - e -gamma1 x t) + A2(1 - e -gamma2 x t), and iii) a time to exhaustion at Pa peak to determine T lim. A biopsy of the vastus lateralis muscle was made before and after training. The training programme consisted in pedalling on a cycle ergometer 2 h a day, 6 days a week, for 4 weeks. Training-induced increases (p < 0.05) in Pa(peak), muscle capillary density, citrate synthase activity, gamma2 that denotes the lactate removal ability (from 0.0547 +/- 0.0038 to 0.0822 +/- 0.0071 min (-1)) and T(lim) (from 299 +/- 23 to 486 +/- 63 s), decreases (p < 0.05) in activities of lactate dehydrogenase (LDH) and muscle type of LDH, the phosphofructokinase/citrate synthase activities ratio and the estimated net amount of lactate released (NALR) during exercise recovery (from 66.5 +/- 8.6 to 47.2 +/- 11.1 mmol) were also observed. The improvement of T (lim) with training was related to the increase in gamma2 (r = 0.74, p = 0.0367) and to the decrease in NALR (r = 0.77, p = 0.0250). These results suggest that the post-training greater ability to remove lactate from the organism and reduced muscle lactate accumulation during exercise account for the concomitant improvement of the time to exhaustion during high-intensity exercise performed at the same relative work rate.

Adult↗

PubMed2005

Rowing performance and estimated training load.

We related the rowing performance and the associated physiological parameters to the training load as estimated by a questionnaire addressing the mean habitual weekly energy expenditure (MHWEE) of twenty-one international and national level oarsmen. The questionnaire also addressed the energy expenditure during training (EET) sessions classified as low- (EE1), moderate- (EE2), and high-intensity (EE3). To evaluate the physiological capability of the oarsmen, they performed incremental exercise to determine their maximal oxygen uptake (V.O(2max)) and the V.O(2) relative to V.O(2max) corresponding to the 4 mmol.l(-1) blood lactate concentration (V.O(2)4 %). The mean work rate sustained during a 2000-m all-out event on a rowing ergometer was considered as the rowing performance. On average, the rowers spent 16.4 +/- 1.0 h.wk(-1) in training with 56 +/- 3 % of the time spent on the water. EET represented 43.5 +/- 1.7 % of MHWEE. Rowing performance and V.O(2max) were both related to MHWEE and EET. Also, rowing performance was related to EE1, EE2, and EE3. In contrast, V.O(2)4 % was not related to the estimated energy expenditures. These results suggest that rowing performance and V.O(2max) are related to training load while V.O(2)4 % was not in the present group of highly trained oarsmen.

Adult↗

PubMed2005

Torque and power-velocity relationships in cycling: relevance to track sprint performance in world-class cyclists.

The aims of the present study were both to describe anthropometrics and cycling power-velocity characteristics in top-level track sprinters, and to test the hypothesis that these variables would represent interesting predictors of the 200 m track sprint cycling performance. Twelve elite cyclists volunteered to perform a torque-velocity test on a calibrated cycle ergometer, after the measurement of their lean leg volume (LLV) and frontal surface area (A(p)), in order to draw torque- and power-velocity relationships, and to evaluate the maximal power (P(max)), and both the optimal pedalling rate (f(opt)) and torque (T(opt)) at which P (max) is reached. The 200 m performances--i.e. velocity (V200) and pedalling rate (f 200)--were measured during international events (REC) and in the 2002 French Track Cycling Championships (NAT). P(max), f(opt), and T(opt) were respectively 1600 +/- 116 W, 129.8 +/- 4.7 rpm and 118.5 +/- 9.8 N . m. P(max) was strongly correlated with T(opt) (p < 0.001), which was correlated with LLV (p < 0.01). V200 was related to P(max) normalized by A(p) (p < or = 0.05) and also to f(opt) (p < 0.01) for REC and NAT. f 200 (155.2 +/- 3, REC; 149 +/- 4.3, NAT) were significantly higher than f(opt) (p < 0.001). These findings demonstrated that, in this population of world-class track cyclists, the optimization of the ratio between P(max) and A(p) represents a key factor of 200 m performance. Concerning the major role also played by f(opt), it is assumed that, considering high values of f 200, sprinters with a high value of optimal pedalling rate (i.e. lower f200-f(opt) difference) could be theoretically in better conditions to maximize their power output during the race and hence performance.

Adult↗

PubMed2004

Peak power output predicts rowing ergometer performance in elite male rowers.

The aim of the present study was to test the hypothesis that peak power output (Ppeak) sustained during maximal incremental testing would be an overall index of rowing ergometer performance over 2000 m (P2000), and to study the influence of selected physiological variables on Ppeak. A group of 54 highly trained rowers (31 heavyweight [HW] and 23 lightweight [LW] rowers) was studied. Body mass, maximal oxygen uptake ((.-)VO(2max)), oxygen consumption corresponding to a blood lactate of 4 mmol. l (-1) expressed in percentage of (.-)VO(2max) (V.O (2)La4 %), and rowing gross efficiency (RGE) were also determined during the incremental test. In the whole group Ppeak was the best predictor of P2000 (r = 0.92, p < 0.0001). Body mass (r = 0.65, p < 0.0001), V.O (2max) (r = 0.84, p < 0.0001), (.-)VO 2)La4 % (r = 0.49, p < 0.0001) and RGE (r = 0.35, p < 0.01) were significantly correlated with P2000 as well. To take the influence of body mass into account, (.-)VO(2max) was related to kg (0.57). Ppeak was significantly related to body mass (r = 0.56, p < 0.0001), (.-)VO(2max) x kg (-0.57) (r = 0.63, p < 0.0001), (.-)VO(2)La4 % (r = 0.45, p < 0.001) and RGE (r = 0.34, p < 0.05). Multiple regression analysis indicated that the above parameters taken together explained 82.8 % of Ppeak variation in the whole group. It was also demonstrated that Ppeak was the best predictor of P2000 when LW and HW groups were considered separately. It was concluded that, by integrating the main physiological factors of performance, Ppeak is an overall index of physiological rowing capacity and rowing efficiency in heterogeneous as well as in homogeneous groups. It presents the further advantage of being easily measured in the field.

Adult↗

PubMed2002

Time to exhaustion at VO(2)max is related to the lactate exchange and removal abilities.

The aim of the present study was to investigate the relationships between lactate exchange and removal abilities and the capacity to prolong exercise, as assessed by the time to exhaustion (Tlim) at a work rate corresponding to VO(2)max (Pa max ). The individual blood lactate recovery curves obtained for 13 untrained subjects after 5 min 90 % Pa max exercise were fitted to the biexponential time function: La(t) = La(0) + A(1) (1-e (-gamma(1) x t) + A(2) (1-e (-gamma(2) x t), where t is time into the recovery, La(0) is the arterialized lactate concentration measured at the end of the exercise, gamma(1) and gamma(2) are velocity constants denoting the lactate exchange and removal abilities, respectively. Tlim was positively related to gamma(1) and gamma(2) (r = 0.60, p < 0.05 and r = 0.56, p < 0.05, respectively) but was negatively related to La(0) (r = 0.75, p < 0.01). gamma()1 was positively related to the capillary density (r = 0.69, p < 0.01) and to the number of capillaries per type I fiber area (r = 0.62, p < 0.05). It was concluded that 1) high lactate exchange and removal abilities would allow continuing a high-intensity exercise for a longer duration, and 2) a high capillary density may explain the associated high lactate exchange ability.

Adult↗

PubMed2002

Leg strength and stiffness as ability factors in 100 m sprint running.

BACKGROUND: The purpose of this study was to determine the importance of leg strength and stiffness relative to i) 100 m sprint performance, ii) mean speed on the three phases of the 100 m race (30-60-100 m) and iii) the speed differences between these phases. METHODS: Nineteen regional to national level male sprinters competed in a 100 m race. Video analysis was used to determine mean velocity parameters. Two subgroups were created since some of the runners decreased their velocity during the third phase (G1), whereas others maintained or accelerated it (G2). Leg strength (concentric half-squats - counter movement jump) and stiffness (hopping) were determined. Simple (r) and multiple regressions (R) were used. RESULTS: The mean performance over 100 m was 11.43 sec (10.72-12.87 sec). The concentric half-squats were related to 100 m (r=0.74, p<0.001) and to the mean speed of each phase (R=0.75, p<0.01). The counter movement jump was related to 100 m (r=0.57, p<0.05) and was the predictor of the first phase (r=0.66, p<0.01). The hopping test was the predictor of the two last phases (R=0.66, p<0.05). Athletes who had the greatest leg stiffness (G1) produced the highest acceleration between the first and the second phases, and presented a deceleration between the second and the third ones. CONCLUSIONS: The concentric half-squats test was the best predictor in the 100 m sprint. Leg stiffness plays a major role in the second phase.

Adult↗

PubMed2002

Influence of changes in nasal ventilation on estimated workload during submaximal field running.

BACKGROUND: Breathe Right (BR) external nasal dilator have become increasingly popular over the past few years, however, the physiological basis for using BR remains unclear. We have examined whether alteration in nasal ventilation would influence the metabolic cost of submaximal running. METHODS: Metabolic cost was estimated in 10 male endurance triathletes by measuring heart rate (HR) and exercise perception by measuring the rate of perceived exertion (RPE) during submaximal field running. The protocol consisted of 5 min of running at 80% of their maximal aerobic velocity (MAV(f), previously determined under field conditions) for three randomised experimental conditions, separated by a 10 min rest. The conditions were normal nasal ventilation (N), no nasal ventilation (using a nose clip) (NC) and with a BR. RESULTS: Running with the BR or with NC did not significantly influence HR (N: 173+/-7, BR: 173+/-8, NC: 172+/-7 beat x min(-1); F=0.01, p=0.99) or RPE (N: 12.1+/-1.7, BR: 11.8+/-1.9, NC: 13.2+/-0.8; F=1.88, p=0.18). We conclude that alteration in nasal ventilation produced by using BR or NC do not influence HR or RPE in a group of triathletes running 5 min at 80% of MAV(f). CONCLUSIONS: The present study tended to demonstrate that both nasal ventilation would not influence the total metabolic cost, and that the BR device is not advantageous during high intensity exercise.

Adult↗

PubMed2001

Response of Blood Lipids to Physical Exercise in Elderly Subjects.

Regular physical activity plays an important role in nonpharmacologic management of hyperlipidemia, in both the primary and secondary prevention of coronary heart disease. Training intensity and duration, health status (especially the presence of cardiovascular disease), and concomitant changes in body mass and dietary habits are the most important factors that can modify the physical activity-blood lipid profile relationship in the elderly. The benefit of regular exercise goes beyond direct influence on blood lipids; it aids in reducing weight, decreasing fat mass, increasing lean body mass, reducing elevated blood pressure, and increasing insulin sensitivity. Regular physical activity has become widely recommended as an important element of healthy and successful aging and should be encouraged in individuals without contraindications. (c)2001 CHF, Inc.

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