Maximal oxygen uptake, ventilatory thresholds and mechanical power during cycling in tropical climate in Guadeloupean elite cyclists.

The Tropical climate imposes a high level of physiological stress, which could modify the target heart rate in training load prescription, as the recommendations are often determined by maximal oxygen uptake testing in temperature-neutral laboratories. To test this hypothesis, 7 high-level cyclists performed two randomised maximal tests in neutral (19.2±0.9°C; 51.7±1.3% RH) and Tropical environment (25.8±1.1°C; 63.7±2.3% RH). Neither maximal oxygen uptake nor ventilatory threshold was influenced by the environmental conditions. However, ventilation (p<0.005) and the respiratory equivalent in O(2) (p<0.05) were significantly higher in the Tropical environment, whereas maximal power output and the time to attain maximal oxygen uptake were significantly lower (p<0.05 for both). Moreover, the ventilatory cost of cycling (expressed in LW(-1)) was significantly greater in the Tropical condition (0.40±0.03LW(-1) vs. 0.32±0.05LW(-1), in Tropical vs. Neutral; condition effect: p<0.005; condition × time: p<0.001). Rectal temperature was influenced by neither the environmental conditions nor exercise (36.7±0.1 and 37.0±0.1°C vs. 36.8±0.1 and 37.1±0.2°C, in Tropical vs. Neutral, before and after exercise) but was influenced by condition × time (p<0.05). The heart rate (HR) values usually used for training prescription were not significantly different (154±5bpm vs. 156±4bpm and 172±4bpm vs. 167±4bpm in Tropical vs. Neutral climate, for the first and second thresholds, respectively). We concluded that the usual parameters measured during maximal exercise to establish training programs are not impaired in moderate Tropical environment. Nevertheless, the thermal stress attested by the increased ventilatory cost of cycling could have prevented the cyclists from performing a true maximal test in Tropical conditions.

Anthropometrical and physiological determinants of performance in French West Indian monofin swimmers: a first approach.

To characterise the anthropometrical and physiological parameters of French West Indian monofin swimmers, seven French West Indian male competitors underwent anthropometrical measurements and physiological testing. The results were analysed in relation with their performances during national and international events (from 50- to 1500-m). We found that both anthropometrical and physiological (aerobic and anaerobic components) factors contributed to the performances of these swimmers. The results demonstrated that certain parameters consistently contributed to the global performance: aerobic parameters (maximal oxygen uptake and the second ventilatory threshold, R (2) = 0.72 and 0.69, respectively), anaerobic parameters (power obtained with the counter-movement jump [R (2) = 0.58] and the force-velocity test [R (2) = 0.54]), leg volume (V1, R (2) = 0.54) and perimeter (P1, R (2) = 0.64), and fat and lean body mass (R (2) = 0.76 and 0.62, respectively). Further studies are needed to compare these determinants of performance in French West Indian and European swimmers and to investigate how they contribute to swimming technique.

Heart rate, thermoregulatory and humoral responses during a 9-day cycle race in a hot and humid climate.

Seven acclimated elite road cyclists were recruited from among the participants in the Tour de Guadeloupe, a 9-day cycle race (D1-D9) held in hot/humid climate (approximately 31 degrees C dry temperature and 76 % relative humidity). Each day of the competition, heart rate (HR) was recorded every 15 s, tympanic temperature (Ttym) was recorded before exercise and immediately at the end of each stage, and body mass loss (BML) was measured by changes in nude body mass at rest and after each stage. Blood lactate concentration [La] was measured at rest and 5 min after each stage. Venous blood samples were collected before the competition and on the 4 th and 8 th days (D4, D8) for hematological and serum determinations and biochemical analyses. No significant differences were found in cardiac, thermoregulatory, or [La] parameters at rest over the 9 days. The subjects spent 31 +/- 6 % of their time below the lactate threshold (LT), 52 +/- 8 % between LT and the onset of blood lactate accumulation (OBLA), and 18 +/- 6 % above OBLA. The increase in Ttym at D3 (0.48 +/- 0.3 degrees C) was significantly lower (p < 0.05) than at D1, D4, D5, and D6. No difference was found for BML between the different stages. Significant increases (p < 0.05) were observed in monocytes at D8 vs. D4 and pre-race values (D0) and in serum Cl-concentration at D4 vs. D0 and D8 (p < 0.05). A significant reduction was observed in mean corpuscular hemoglobin concentration (MCHC) at D8 and D4 vs. D0 (p < 0.01). No difference was found in other blood parameters at D0, D4, or D8. Taken together, these results suggest that a consecutive 9-day cycle competition in hot/humid climate did not alter homeostasis at rest in acclimated well-trained cyclists. No major effect of repeated cycling stages on thermoregulatory and blood parameters was observed during the Tour de Guadeloupe. Further research is needed to compare the cardiac adaptations of natives to tropical climate and un-acclimated subjects during long-duration exercise.

Effect of an acute hot and dry exposure in moderately warm and humid environment on muscle performance at different times of day.

This study investigated whether 30 min of acute hot exposure has an additional passive warm-up effect for the improvement in muscle performance in a moderately warm and humid environment. We also sought to determine whether this effect is dependent on the diurnal variation in body temperature. Nine male subjects (age: 31.9 [+/- 5] years, height: 177 [+/- 6] cm, body mass: 69.3 [+/- 10] kg) were tested (CMJ, cycling sprints, and isokinetic contractions of the knee flexors and extensors) in a moderately warm and humid environment (24 [+/- 1] degrees C and 70 [+/- 4] % rh) with and without acute heat exposure (30 min of rest in a sauna at 76 [+/- 2] degrees C and 27 [+/- 1] % rh), both in the morning (07:00 - 09:00 h) and in the evening (17:00 - 19:00 h). Our results indicated a significant effect of both time-of-day and acute heat exposure on leg skin temperature (p < 0.01) but failed to show any effect of time-of-day or acute heat exposure on the various evaluated parameters (CMJ: speed, force, power and height; cycling power: over a half pedal revolution and a total pedal revolution; isokinetic torque: knee extensor and flexor muscles at 4.19 rad x s (-1), 3.14 rad x s (-1), 2.09 rad x s (-1), and 1.05 rad x s (-1)). In conclusion, our data suggest that 30 min of acute hot exposure does not have any passive warm-up effect in a moderately warm and humid environment. Furthermore, the diurnal variation in body temperature has no passive warm-up effect in a moderately warm and humid or in an extremely hot environment.

Effects of adding a preceding run-up on performance, blood lactate concentration and heart rate during maximal intermittent vertical jumping.

In this study, we examined the effects of a prior run-up on intermittent maximal vertical jump performance. Seven regionally ranked male volleyball players volunteered to participate in the study. They performed three randomized tests: (1) six repeated intermittent maximal jumps (jump condition), (2) six repeated intermittent run-ups (run-up condition), and (3) six repeated run-ups followed by maximal jumps (run-up plus jump condition). All performances were assessed and blood lactate concentration and heart rate were measured before and after each of the tests. Mean ( +/- ) jump performance (64.7 +/- 2.3 cm) increased significantly (P = 0.02) over the course of the jump condition and was significantly higher (P < 0.001) than for the run-up plus jump condition (58.0 +/- 3.2 cm), which tended to decrease with repetition. Blood lactate concentration was significantly higher in the run-up plus jump condition (3.73 +/- 0.24 mmol . l(-1)) than in the jump (2.61 +/- 0.26 mmol . l(-1), P = 0.02) and run-up (2.86 +/- 0.18 mmol . l(-1), P = 0.03) conditions. The increase in heart rate was significantly higher both in the run-up plus jump condition (33 +/- 6 beats . min(-1), P = 0.05) and run-up condition (33 +/- 4 beats . min(-1), P = 0.02) than in the jump condition (21 +/- 3 beats . min(-1)). The results indicate that the addition of run-ups probably impeded performance in the repetition of vertical jumps.

Time-of-day effects on anaerobic muscular power in a moderately warm environment.

This study evaluated the influence of a neutral vs. a moderately warm environment on the diurnal variation in muscular power. Twelve male subjects [27.0 (+/-4) years] performed two different jump tests [a squat jump (SJ) and a counter-movement jump (CMJ)] and a brief maximal sprint on cycle ergometer (CS) in four different conditions (morning/neutral, morning/moderately warm and humid, afternoon/neutral, and afternoon/moderately warm and humid). The morning experiments were conducted between 07:00 and 09:00 h, and the afternoon experiments were conducted between 17:00 and 19:00 h. The mean laboratory temperatures and humidity were 20 (+/-1) degrees C, 70 (+/-5)% and 29 (+/-1) degrees C, 57 (+/-4)% for the neutral and moderately warm and humid conditions, respectively. Rectal temperature and leg skin temperature were significantly dependent on both time-of-day and ambient temperature. An interaction effect (P < 0.05) was noted between time-of-day and ambient temperature for the power developed for the CMJ, the SJ, and half of a pedal revolution during the cycling sprint. In summary, (i) the same subjects were influenced by time-of-day differently, depending on the ambient temperature during testing; (ii) time-of-day affected muscular performance only in the neutral condition, (iii) the moderately warm and humid condition blunted the diurnal variation in muscular performance, and (iv) the effect of the ambient temperature was dependent on time-of-day.

Effects of 8 days acclimation on biological and performance response in a tropical climate.

BACKGROUND: This study was designed to determine the acclimation process elicited by exposure to a tropical climate. METHODS: Nine triathletes performed 3 outdoor indirect continuous running multistage tests in both thermoneutral and tropical conditions. Before travelling to the tropical area (Martinique Island, FWI), the triathletes performed the thermoneutral test (TN) in 14 degrees C and 45% rh conditions. The tropical tests were performed 2 and 8 days after arrival (T2 and T8, performed at a mean environmental temperature of 33.4 degrees C and 75.5% rh). The day before T8, blood samples were drawn for biochemical analysis. During each test, tympanic temperature, sweat rate, weight loss, heart rate (HR), and performance were recorded. RESULTS: The results demonstrated that: 1) the mean tympanic temperature was greater in T2 (p<0.001) and T8 (p<0.01) than in TN; 2) the mean sweat rate was significantly greater (p<0.001) in T2 and T8 than in TN and significantly greater in T8 than in T2 (p<0.03); 3) the weight loss after trials was significantly greater (p<0.001) in T2 and T8 than in TN and in T8 than in T2 (p<0.04); 4) the mean HR and the HR at rest were significantly greater in T2 than in TN (p<0.001) and T8 (p<0.005); 6) significant reductions were observed in T8 vs TN in red cell count (p<0.05) and plasma proteins (p<0.04), the consequence of a 7.5% plasma volume expansion; and 7) the performance was significantly lower in both T2 (p<0.02) and T8 (p<0.03) than in TN. CONCLUSIONS: We concluded that 8 days exposure to hot/wet conditions induced impairments in physiological responses and performance that were still evident on the 8th day. Further and longer outdoor studies are needed to investigate if return to optimal performance levels after adaptation to hot/wet conditions is possible.

Time-of-day effects in maximal anaerobic leg exercise in tropical environment: a first approach.

The aim of this study was to establish the effect of time of day on maximal anaerobic leg power in a tropical environment (French West Indies). Twenty-three physical education students (15 males and 8 females) who trained 10.5 hours a week (SD 6) volunteered to participate in the study. Their mean age, height and body mass were 22.8 (SD 3) years, 172.6 (SD 8) cm, and 64.6 (SD 7) kg, respectively. The chronotype of all subjects was moderate or intermediate. Tests were scheduled at 08 : 00, 13 : 00 and 17 : 00 hours on separate days in random order and constant conditions (room temperature: 28.1 degrees C [SD 0.6], relative room humidity: 62.6 % [SD 3.4]). On test days, the subjects were first measured at rest for body mass, heart rate and rectal temperature and they then performed vertical jump tests and a force-velocity test. The results showed a time-of-day effect on rectal temperature, which was significantly (p < 0.005) higher by the afternoon (13 : 00 and 17 : 00) than the morning (08 : 00). However, our results failed to show any daytime variation in maximal anaerobic power under the influence of tropical climate, which suggests that a hot and humid environment may have blunted the time-of-day effect by a passive warm-up effect.

Effect of sleep deprivation on shuttle run score in middle-aged amateur athletes. Influence of initial score.

AIM: The aim of the present study was to investigate the effect of sleep deprivation on shuttle run score (corresponding to an estimated VO2 peak) in middle-aged amateur athletes. METHODS: Twenty-two athletes, training 9.2 hours a week (+/-4), performed a Leger and Gadoury shuttle test daily in a 4-day series that included a pre-test in day 0, 28 hours without sleep before test 1 (and 10 another hours after the test and before bedtime for a sleep deprivation of 38 hours), and then 10 hours of sleep before each of days 2 and 3. RESULTS: Shuttle run score showed no significant difference over the 4 days; however, the change in shuttle run score on day 2 was significantly correlated with the initial score. CONCLUSIONS: This result suggests that effect of sleep deprivation on shuttle run score is dependent on initial score and may encourage high level aerobic athletes to avoid sleep deprivation 2 days before a competition.

Effect of tropical climate on performance during repeated jump-and-reach tests.

AIM: The aim of the present study was to determine the effect of tropical climate (i.e., hot and humid) on performance during multiple jump-and-reach tests. METHODS: Fourteen male basketball players volunteered to perform 2 randomized series of jump-and-reach tests, which consisted of a jump-and-reach test every 15 sec for 5 min (21 jump-and-reach tests) in two thermal conditions: tropical (TR, 30.4 degrees C, 70% rh) and thermoneutral (TN, 23.1 degrees C, 53% rh). During each test, lactate concentration [La(-)], tympanic temperature (Tty), sweat rate (SR), heart rate (HR), and performance (height: H) were noted at rest, during exercise and recovery. Two hours of recovery separated the TN and TR tests. RESULTS: There were no significant differences in mean height, maximal height or the kinetics between TN and TR. Both conditions induced an increase in height over time (time effect: p<0.002). There were no significant differences in [La(-)] at rest or during exercise or recovery in the 2 conditions. Both conditions induced an increase in [La(-)] (time effect: p<0.002). There was a tendency toward a higher mean [La(-)] during TR than TN (situation effect, p<0.07). However, compared to resting values, [La(-)] values were significantly increased only in TR and not in TN. Tty, was significantly greater (p<0.001) at rest and during exercise and recovery in TR than in TN. SR and HR were also significantly greater at rest and during exercise and recovery in TR (p<0.001 for SR and HR). CONCLUSION: We conclude that tropical climate affects physiological responses without improving or decreasing performance during successive jump tests.

Alactic anaerobic performance in subjects with sickle cell trait and hemoglobin AA.

The aim of the present study was to assess the performance of subjects with sickle cell trait (SCT) during brief and explosive exercise involving mainly anaerobic metabolism. One hundred and ninety-six black subjects underwent SCT screening, which revealed the presence of 16 subjects with SCT and 180 subjects with normal hemoglobin (HbAA). All subjects performed four tests: 1) a 100-m sprint, 2) a long-jump, 3) a Leger-Boucher shuttle test and 4) a jump-and-reach test. A control group (n = 18) selected from the 180 subjects with HbAA was matched according to the sex, age, weight and height of the SCT subjects (SCTs). The performances of the SCTs (n = 16) were compared with those of the control group. The performances were similar between the SCTs and control group for the sprint test, long-jump and the Leger-Boucher shuttle test. There was, however, a significant difference for the jump-and-reach test between the two groups: the SCTs (i. e., males plus females, and males and females considered separately) reached a significantly greater height (p < 0.05) than the matched subjects of the control group (63.7 +/- 3.6 vs. 58.6 +/- 3.1 cm, 72.3 +/- 3.9 vs. 67.1 +/- 2.4 cm and 52.7 +/- 3.2 vs. 45.3 +/- 2.0 cm for SCTs versus non-SCTs, for the group, the males and the females, respectively). The results of the present study suggest that the performance of brief and explosive exercise may be enhanced by HbS.

Effect of recovery duration on the force-velocity relationship.

The aim of this study was to investigate the effect of different Recovery Duration (RD) between each sprint (30 s, 1 min, 3 min, 5 min, 10 min and 24 h) during the force-velocity test and to analyse associated anaerobic parameters such as maximal anaerobic power and blood lactate concentrations. Twelve male physical education students aged from 18 to 26 years took part in this study. Maximal anaerobic power (Pmax) was not statistically different whatever the recovery duration (from 885 to 938 watts, for RD 30 s to RD 24 h, respectively). This was associated with a tendency during the longer RD tests for optimal velocity to decrease (p = ns) while optimal force increased (p < 0.05). Blood lactate concentrations were regularly increased from 1.7 to a 9 mmol x l(-1) plateau at sprint 4 for RD tests < 10 min and were quite stable from the second sprint with an associated value from 2.2 to 4.7 mmol x l(-1) for RD 10 min and RD 24 h. In spite of statistically different values for [L]s between the tests, the power developed for each sprint remained unchanged. These data indicate that the attainment of maximal power seems independent from the recovery duration (> 10 s) and the pre-blood lactate values observed between each sprint during the force-velocity test. The way to reach Pmax was different between the tests. Different partition of energetic pathways are suggested. In conclusion, the force-velocity test could be performed with a shorter and the arbitrary five minutes recovery duration.

Serum insulin-like growth factor I and physical performance in prepubertal Bolivian girls of a high and low socio-economic status.

The aim of the study was to determine if a decrease in serum insulin-like growth factor I (Igf-I) levels under marginal malnutrition is responsible for the lower physical performance of girls of a low socio-economic status (LSES). Girls were selected after physical examination (Tanner's stage 1) and anthropometric measurements (height, body mass or mb, body mass index or BMI = mb height2). Lean body mass mb,1 was measured after skinfold thickness determination; serum IGE-I, by radioimmunoassay; maximal O2 consumption, (VO2max), directly during incremental exercise up to exhaustion; and maximal aerobic power (Wmax), using the force-velocity test. LSES girls (n = 31) had been malnourished in the past and, currently, were suffering from marginal malnutrition: they were smaller (135.2 +/- 5.5 vs 146.1 +/- 4.3 cm), lighter (31.7 +/- 3.9 vs 37.6 +/- 5.0 kg), exhibited a lower mb,1 (24.2 +/- 2.5 vs 27.5 +/- 3.0 kg) but same BMI compared with HSES (high socio-economic status) girls (n = 32). Igf-I levels (27.7 +/- 7.9 vs 34.1 +/- 6.5 nmol.1(-1), VO2max (45.26 +/- 4.72 vs 50.74 +/- 6.02 ml. min-1.kg-1 LBM) and Wmax (6.00 +/- 1.15 vs 8.70 +/- 1.53 W.kg-1 mb,1 were lower in LSES girls. Moreover, the differences in every parameter were not the consequence of the younger age (10.8 +/- 0.9 vs 11.2 +/- 0.6 years) of the LSES girls. Our results provide evidence that the lower Wmax of undernourished prepubertal girls was partly the consequence of alterations in muscle function at the qualitative level, as a result of a decrease in Igf-I levels. Conversely, under normal nutritional conditions, anthropometric characteristics only are explicatory factors for physical performances.

Effect of altitude and socioeconomic status on VO2max and anaerobic power in prepubertal Bolivian girls.

The aim of this work was to evaluate the effects of high altitude and low socioeconomic status (SES) on aerobic and anaerobic power in 11-yr-old Bolivian girls. At both high (3,600 m) and low (420 m) altitudes, low-SES groups of girls were compared to similarly aged, high-SES girls. At low altitude, low-SES girls were also compared with younger high-SES girls with the same anthropometric characteristics. Anthropometric data were similar between high-SES and low-SES girls at both altitudes, but low-SES girls showed a 9-mo growth delay. Maximal O2 uptake was significantly lower for low-SES girls at both altitudes. Values did not differ when expressed relative to body weight at high altitude for high-SES vs. low-SES girls (37.6 +/- 1.2 vs. 39.3 +/- 1.0 ml.min-1.kg body wt-1), but a difference persisted at low altitude between high- and low-SES girls (37.5 +/- 1.0 vs. 34.7 +/- 0.7 ml.min-1.kg body wt-1). Anaerobic power (Pmax, force-velocity test; Pwing, Wingate test) was reduced for low-SES girls at both altitudes, whatever the mode of expression. For a given SES, the relative anaerobic performances were lower at low altitude. At low altitude, low-SES girls developed lower anaerobic power than did younger high-SES girls with similar anthropometric characteristics. In conclusion, at both altitudes, the reduction of anaerobic performances observed in girls of low SES could not be totally explained by anthropometric factors. Structural and/or functional muscle alterations are suggested. Moreover, at low altitude, tropical and other factors may have contributed to differences in performance between low- and high-SES girls.

The effect of acute hypoxia at low altitude and acute normoxia at high altitude on performance during a 30-s Wingate test in children.

The effect of acute hypoxia (FIO2 = 0.137 +/- 0.001) at Low Altitude (LA: Clermont-Ferrand, 330 m) and acute normoxia (FIO2 = 0.306 +/- 0.006) at High Altitude (HA: La Paz, 3600 m) on performance during a 30-s Wingate test has been investigated in prepubertal children (Tanner stage 1). Twenty five boys (LA, n = 10; HA, n = 15) aged from 10.6 to 12.7 years performed two Wingate tests at random: at LA, one in normoxia (ambient air) and one in acute hypoxia and at HA, one in chronic hypoxia (ambient air) and one in acute normoxia. The subjects performed the two tests using the same calibrated cycle ergometer. Peak Power (PP), Mean Power (MP), O2 uptake during the 30 s (VO2) and blood lactate accumulation (delta [L]s) were measured. Compared to normoxia, acute hypoxia at LA did not alter PP (8.0 +/- 1.1 vs 7.9 +/- 1.3 W.kg-1 BW) and MP (6.1 +/- 0.7 vs 6.1 +/- 1.1 W.kg-1 BW). Similarly, compared to chronic hypoxia, acute normoxia at HA did not modify these parameters (PP: 7.4 +/- 1.5 vs 7.3 +/- 1.8; MP: 5.4 +/- 1.2 vs 5.5 +/- 1.1; W.kg-1 BW). VO2 and delta [L]s were neither significantly changed by acute hypoxia at LA (520 +/- 50 vs 550 +/- 60 ml O2; 5.3 +/- 1.7 vs 4.8 +/- 1.7 mmol.l-1) nor by acute normoxia at HA (530 +/- 110 vs 500 +/- 90 ml O2; 3.4 +/- 1.3 vs 3.3 +/- 1.0 mmol.l-1).(ABSTRACT TRUNCATED AT 250 WORDS)