Biomedical subjects

S Berthoin

Publications and source records attributed to S Berthoin.

14 recordsLinked to original sources

PubMed2003

Time spent at VO2max: a methodological issue.

This study was designed to propose a standardised procedure to determine the time spent at VO2max (tVO2max) based on the VO2max of the day (i. e. the VO2max value measured the day of the test). Ten male subjects first performed a graded field test, followed by a continuous running exercise to exhaustion, at the velocity of the Université de Montréal Track Test (V(UMTT)) plus 1 km x h(-1) (V(UMTT)(+1)). The second test consisted of an exhaustive run at 100 % of V(UMTT), followed by a V(UMTT)(+1) test. Different methods were used to compare time spent at VO2max, based on the VO2max of the graded field test, and time spent at VO2max, based on the VO2max of the day, during an exhaustive run at 100 % of V(UMTT). Results have shown that V(UMTT)(+1) tests were of sufficient intensity and duration to identify the VO2max of the day. Time spent at VO2max ranged from 25 +/- 53 s to 139 +/- 76 s according to the method used. However, the tVO2max method based on the sum of each value higher than 95 % of VO2max of the day appeared more robust than methods based on the time to exhaustion minus time to reach VO2 reference value, or the method based on the sum of values higher than VO2max minus 2.1 ml x kg(-1) x min(-1).

Adult↗

PubMed2003

Plasma lactate and plasma volume recovery in adults and children following high-intensity exercises.

AIM: To compare plasma lactate concentration recovery kinetics when measured and corrected for variations in plasma volume between children and adults. METHODS: Nine boys (11.3 +/- 1.1 y) and 8 men (21.9 +/- 1.9 y) performed a maximal and a supramaximal exercise until exhaustion. Plasma lactate concentrations, haemoglobin and haematocrit were measured at rest, immediately on completion of exercise and after the 2nd, 5th, 12th and 30th minute of recovery. The plasma lactate concentrations and the rate of recovery were corrected for variations in plasma volume. RESULTS: The maximal decreases in plasma volume were significantly higher in adults than in children for maximal exercise (-18.7 +/- 2.6% vs -14.5 +/- 3.2%; p < 0.05), but similar for the supramaximal exercise (-16.9 +/- 3.4% vs -15.2 +/- 3.4%). During recovery, measured and corrected plasma lactate concentrations were significantly higher in adults. The rate of plasma lactate recovery was higher in adults for maximal exercise only. The same results were obtained when the rates of plasma lactate decrease were calculated from corrected plasma lactate concentrations. CONCLUSION: The correction of the plasma lactate concentrations for variations in plasma volume did not influence the comparison of the concentrations obtained in adults and children, or their rate of recovery.

Adult↗

PubMed2002

Effects of high intensity intermittent training on peak VO(2) in prepubertal children.

This study was designed to examine peak VO(2) responses of prepubescent children following a 7-week aerobic training. Twenty-three boys and thirty girls (9.7 +/- 0.8 years) were divided into a high intensity experimental group (HIEG: 20 girls and 13 boys) and a control group (CG: 10 girls and 10 boys). A graded 20-m shuttle run with measurement of gas exchange values was performed prior to and after the 7-week training program. The test consisted of a 3-min run at 7 km x h(-1) to determine energy cost of running, immediately followed by a 20-meter shuttle run test. HIEG had two 30 min-sessions of short intermittent aerobic training per week at velocities ranging from 100 up to 130 % of the maximal aerobic speed. For HIEG, absolute peak VO(2)(9.1 %) and relative to body mass peak VO(2)(8.2 %) increased significantly (p < 0.001); it was unchanged in the CG. Similarly, maximal shuttle run improved significantly in HIEG (5.1 %, p < 0.001). In contrast, there was no significant change for CG. For both groups energy cost of running remained unchanged. These findings show that prepubescent children could significantly increase their peak VO(2) and maximal shuttle velocity with high intensity short intermittent aerobic exercises.

Age Factors↗

PubMed2002

Plasma lactate recovery from maximal exercise with correction for variations in plasma volume.

BACKGROUND: To compare plasma lactate concentrations and plasma lactate kinetics during recovery, for measured and corrected values for changes in plasma volume, after a maximal aerobic exercise. METHODS: Sixteen male subjects performed an incremental and maximal exercise in order to reach maximal aerobic power. Prior to the exercise, at the end and during recovery (2, 5, 12 and 30 min), blood samples were collected through an antecubital catheter. Samples were analysed for lactate, hematocrit and hemoglobin in order to calculate changes in plasma volume. Plasma lactate concentrations ([La]p) were corrected for changes in plasma volume. Plasma lactate kinetics was estimated through the ratio between [La]p after 5 min recovery minus [La]p after 30 min to time (25 min) and expressed in percentage per minute. RESULTS: Maximal changes in plasma volume (-19.7 +/- 3.8%) were correlated to maximal measured [La]p (r=0.66, p<0.01). Maximal measured [La]p values (14.9 +/- 2.6 mmol x l-1) were 17.3% higher (p<0.001) than corrected values (12.7 +/-2.0 mmol x l-1). The kinetics of [La]p decrease was significantly higher (p<0.001) for measured values (2.38 +/- 0.29 % x min-1) than for corrected values (2.22 +/- 0.33 % x min-1). CONCLUSIONS: These results suggested that changes in plasma volume must be taken into account when peak postexercise plasma lactate concentration or lactate recovery curves are analysed.

Adult↗

PubMed2001

Relationship between run times to exhaustion at 90, 100, 120, and 140% of vVO2max and velocity expressed relatively to critical velocity and maximal velocity.

The aim of the present study was to explain the inter-individual variability in running time to exhaustion (tlim) when running speed was expressed as a percentage of the velocity, associated with maximal oxygen uptake (vVO2max). Indeed for the same percentage of vVO2max the anaerobic contribution to energy supply is different and could be dependent on the critical velocity (Cv) and also on the maximal running velocity (vmax). Ten subjects ran four tlim at 90, 100, 120, and 140% of vVO2max; mean and standard deviation for tlim were 839 +/- 236 s, 357 +/- 110 s, 122 +/- 27 s, and 65 +/- 17s, respectively. Each velocity was then expressed 1) as a percentage of the difference between vVO2max and Cv (%AeSR); 2) as a percentage of the difference between vmax and Cv (%MSR); 3) as a percentage of the difference between vmax and vVO2max (%AnSR). Highest correlations were found between tlim90 and tlim100 and velocity expressed as %MSR (r = -0.82, p < 0.01 and r = -0.75, p < 0.01), and between tlim120 and tlim140 and velocity expressed as %AnSR (r = -0.83, p < 0.01 and r = -0.94, p < 0.001). These results show that the same intensity relative to aerobic contribution did not represent the same absolute intensity for all and could partly explain variability in tlim. Therefore expressing intensity as a percentage of MSR for sub-maximal and maximal velocities and as a percentage of AnSR for supra-maximal velocities allows individual differences in anaerobic work capacity to be taken into account and running times to exhaustion to be predicted accurately.

Adult↗

PubMed2001

High-intensity aerobic training during a 10 week one-hour physical education cycle: effects on physical fitness of adolescents aged 11 to 16.

The aim of this study was to analyse the effects of a high-intensity aerobic training program on different components of physical fitness in adolescents aged 11 to 16 years. The subjects were divided into a high intensity (HI) group (243 girls and 260 boys) and a control (C) group (21 girls and 27 boys). HI and C completed a weekly 3 hour physical education (PE) session. Before and after a 10-week period, the two groups performed the European physical fitness test battery (EUROFIT). During these 10 weeks HI spent one hour out of three at a specific PE session. These specific sessions consisted of short intermittent exercises (10 seconds) at 100 to 120% of maximal aerobic speed. They showed a significant influence on standing broad jump (2.9 %, P<0.05, F=4.85), 20 meter shuttle run (3.8%, p0.001, F=23.21) and on the maximal distance covered over 7 min (7.6 %, P< 0.001, F= 14.48). For C there was no improvement in EUROFIT performances. It was concluded that training at high intensity improves not only children's aerobic fitness but also performance of standing broad jump. Well-monitored, adequate intensive training is necessary for a more desirable functional development.

Adolescent↗

PubMed2001

Predicting sprint kinematic parameters from anaerobic field tests in physical education students.

The relations among kinematic parameters measured during the first 10 seconds of 100-m sprint and anaerobic tests were studied in 22 male physical education students. During the first 10 seconds of the sprint, the position of the runners was "continuously" measured with a laser telemeter. Maximal acceleration (Amax), maximal velocity (Vmax), and time to reach Vmax (tVmax) were derived from position data. In addition, the subjects performed anaerobic tests: squat jump (SJ), countermovement jump (CMJ), and force-velocity test to measure maximal power, maximal theoretical cranking velocity (VO), maximal theoretical isometric force, and the Wingate anaerobic test (30 seconds). The mean 100-m run time of the subjects was 12.6 +/- 0.9 seconds. The highest correlations were calculated between Amax and V0 (r = 0.55, p < 0.01) and CMJ (r = 0.48, p < 0.05) and Vmax and SJ (r = 0.63, p < 0.01) and CMJ (r = 0.56, p < 0.05). The tVmax was uncorrelated to other tests. Because the CMJ was the anaerobic performance best correlated to the different kinematic parameters of the run, our results fail to identify one anaerobic test that specifically explains one sprint kinematic parameter.

Adult↗

PubMed2000

Oxygen kinetics and modelling of time to exhaustion whilst running at various velocities at maximal oxygen uptake.

The purpose of this study was to characterise the relationship between running velocity and the time for which a subject can run at maximal oxygen uptake (VO2max), (tlimVO2max). Seven physical education students ran in an incremental test (3-min stages) to determine VO2max and the minimal velocity at which it was elicited (vVO2max). They then performed four all-out running tests on a 200-m indoor track every 2 days in random order. The mean times to exhaustion tlim at 90%, 100%, 120% and 140% vVO2max were 13 min 22 s (SD 4 min 30 s), 5 min 47 s (SD 1 min 50 s), 2 min 11 s (SD 38 s) and 1 min 12 s (SD 18 s), respectively. Five subjects did not reach VO2max in the 90% vVO2max test. All the subjects reached VO2max in the runs at 100% vVO2max. All the subjects, except one, reached VO2max in the runs at 120% vVO2max. Four subjects did not reach VO2max in the 140% vVO2max test. Time to achieve VO2max was always about 50% of the time to exhaustion irrespective of the intensity. The time to exhaustion-velocity relationship was better fitted by a 3- than by a 2-parameter critical power model for running at 90%, 100%, 120%, 140% vVO2max as determined in the previous incremental test. In conclusion, tlimVO2max depended on a balance between the time to attain VO2max and the time to exhaustion tlim. The time to reach VO2max decreased as velocity increased. The tlimVO2max was a bi-phasic function of velocity, with a peak at 100% vVO2max.

Adult↗

PubMed1999

Determination of the velocity associated with the longest time to exhaustion at maximal oxygen uptake.

The so-called velocity associated with VO2max, defined as the minimal velocity which elicits VO2max in an incremental exercise protocol (v(VO2max)), is currently used for training to improve VO2max. However, it is well known that it is not the sole velocity which elicits VO2max and it is possible to achieve VO2max at velocities lower and higher than v(VO2max). The goal of this study was to determine the velocity which allows exercise to be maintained the longest time at v(VO2max). Using the relationship between time to exhaustion at VO2max in the all-out runs at 90%, 100%, 120% and 140% of v(VO2max) and distance run at VO2max, the velocity which elicits the longest time to exhaustion at VO2max (CV') was determined. For the six subjects tested (physical education students), this velocity was not significantly different from v(VO2max) (16.96+/-0.92 km x h(-1) vs 17.22+/-1.12 km x h(-1), P = 0.2 for CV' and v(VO2max), respectively) and these two velocities were correlated (r = 0.88, P = 0.05).

Adult↗

PubMed1999

Validity of the Université de Montréal Track Test to assess the velocity associated with peak oxygen uptake for adolescents.

BACKGROUND: The purpose of the study was to test the ability to determine the velocity associated with peak oxygen uptake for adolescents by means of a simple field test, the Université de Montréal Track Test (UMTT). METHODS: Fifteen adolescents, 13.4 +/- 1.0 years, performed two maximal field tests where oxygen uptake and heart rate were continuously monitored. The first test (graded field test, first stage 8 km.h-1, increment 1.5 km.h-1, duration 3 min) allowed the subjects to reach a steady-state oxygen uptake. Then, the velocity associated with peak oxygen uptake was calculated from the ratio between peak oxygen uptake above resting level to energy cost of running. The calculated velocity was kept as the criterion velocity. For the second test (UMTT, first stage 8 km.h-1; increment 1 km.h-1; duration 2 min), the velocity measured at the last completed stage was retained. RESULTS: The measured peak oxygen uptake for the graded field test (51.8 +/- 6.5 ml.kg-1.min-1) and for the UMTT (51.0 +/- 7.9 ml.kg-1.min-1) were not significantly different. The calculated velocity (12.9 +/- 1.0 km.h-1) and the measured velocity (12.7 +/- 0.9 km.h-1) were not significantly different and were significantly correlated (r = 0.80, p < 0.001). CONCLUSIONS: It was concluded that, for adolescents, the velocity measured at the last completed stage of the UMTT allows a valid estimation of the velocity associated with peak oxygen uptake.

Adolescent↗

PubMed1997

Swimming performances and stroking parameters in non skilled grammar school pupils: relation with age, gender and some anthropometric characteristics.

OBJECTIVE: It was hypothesized that swimming velocity (V) and stroking parameters such as stroke length (SL), stroke rate (SR) and stroke index (SI) are influenced by age, gender, and some anthropometric characteristics. EXPERIMENTAL DESIGN: Cross-sectional study. SETTING: Grammar school pupils from French schools. PARTICIPANTS: One thousand and ninety-seven males and 961 females non skilled swimmers aged from 11 to 17. INTERVENTIONS: Usual swimming sessions (6 +/- 2 h.year-1) during a physical education program at school. MEASURES: V, SL, SF and SI (SI = V.SL) were measured or calculated from a 50-m crawl sprint and height, arm span and body mass were measured for all subjects. RESULTS: The results showed that V, SL and SI increased regularly (p < 0.01) in relation to age in both genders. SL was never significantly different between males and females. SF remained unchanged according to age and was significantly higher in males than in females. V, SL and SI were influenced by age and arm span but not SF. CONCLUSIONS: As males and females were submitted to the same swimming teaching program at school, a higher increase in muscle power and anaerobic capacity in males could explain the gender differences. These results observed in non skilled swimmers showed that the differences in stroking parameters between genders were the reverse of those of top level swimmers and that they can be used by swimming teachers in order to build some assessment tools and to better understand the improvements in swimming in relation to growth and gender.

Adolescent↗

PubMed1996

Comparison of maximal aerobic speed as assessed with laboratory and field measurements in moderately trained subjects.

In order to compare the Maximal Aerobic Speed (MAS) evaluated with different methods, eleven male physical education students (22.2 +/- 3.0 years) were submitted to a maximal treadmill protocol and to the Université de Montréal Track Test (UMTT). Four methods were used to calculate MAS. After treadmill measurement of VO2max, MAS was calculated (MAS_calc) by the following formula: MAS_calc = (VO2max - 0.083)/C, where VO2max is the maximal oxygen uptake (ml.kg-1.s-1) and C the energy cost of running (ml.kg-1.m-1). The extrapolated MAS (MAS_ex) was obtained from the measured VO2max and by extrapolation of the VO2 versus speed relationship. The MAS for treadmill measurement (MAS_tr) and for UMTT (MAS_UMTT) were the velocities at the last completed stages. The average MAS_calc (4.71 +/- 0.48 m.s-1), MAS_ex (4.62 +/- 0.48 m.s-1), MAS-tr (4.75 +/- 0.57 m.s-1) and MAS_UMTT (4.64 +/- 0.35 m.s-1) were not significantly different and were significantly correlated, between 0.85 (MAS_ex vs MAS_UMTT) and 0.99 (MAS_calc vs MAS_tr), with p < 0.001 in both cases. MAS measurements were significantly correlated to measured VO2max but independent of C.

Adult↗

PubMed1995

Effect of a 12-week training programme on Maximal Aerobic Speed (MAS) and running time to exhaustion at 100% of MAS for students aged 14 to 17 years.

The aims of this study were to use the Maximal Aerobic Speed (MAS) to set training intensities for aerobic training and to measure the effects of two different training programmes on MAS and on the running time to exhaustion at 100% of MAS (Tlim) for 121 students aged 14 to 17 years. The MAS was measured using the Université de Montréal Track Test (UMTT). This measurement was found reproducible for males (r = 0.93) and females (r = 0.68). The Students followed a 12-week training programme of one weekly training session. The MAS and the Tlim were measured the weeks before and after training. Two training programmes were proposed (intense training programme and moderate training programme). These training programmes differed by the ratio between continuous exercises (85% of MAS) and intermittent exercise (between 90% and 120% of MAS). For the moderate training programme, the ratio between continuous and intermittent exercises was greater than for the intensive training programme. Twenty subjects served as control group. The students MAS and Tlim (mean +/- SD) were respectively 13.7 +/- 1.6 km.h-1 and 380.5 +/- 91.8 s for the males and 11.3 +/- 1.2 km.h-1 and 347.2 +/- 91.1 s for the females. Our results indicated that only the subjects of the intense training group improved their MAS: + 5.7% for the males (p < 0.001) and + 5.4% for the females (p < 0.001). In neither case was Tlim significantly improved with training. In conclusion, we can notice that MAS is a pertinent criterion to set training intensities for aerobic training and that a weekly training session over 12 weeks is sufficient to moderately improve the MAS of initially untrained students.

Adolescent↗

PubMed1994

Comparison of two field tests to estimate maximum aerobic speed.

The measurement of maximal aerobic speed (MAS) and the prediction of maximal oxygen uptake (VO2 max) by means of field tests were carried out on 17 students studying physical education. The subjects underwent a continuous multi-stage track test (Léger and Boucher, 1980), shuttle test (Léger et al., 1984) and VO2 max measurement on a treadmill. The VO2 max values estimated using the track test (56.8 +/- 5.8 ml kg-1 min-1) were not significantly different from the values measured in the treadmill test (56.8 +/- 7.1 ml kg-1 min-1), but were higher than those estimated using the shuttle test (51.1 +/- 5.9 ml kg-1 min-1). The maximal nature of the tests was checked by measurement of heart rate and lactate concentration, taken within 2 min post-test. The means of the MAS observed in the track test (15.8 +/- 1.9 km h-1) and in the treadmill test (15.9 +/- 2.6 km h-1) were not significantly different (P > 0.10). The mean of the shuttle test MAS (13.1 +/- 1 km h-1) was significantly lower (P < 0.01) than those of the other tests. However, the MAS of the shuttle test and track test are linked. The equation for linear regression between MAS values in these two tests is MAStrack = 1.81 x MASshuttle -7.86 (r = 0.91), allowing estimation of one of these MAS values when the other is known. Thus these values may be used within diversified training.

Adolescent↗