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Biomedical subjects

J Larue

Publications and source records attributed to J Larue.

9 recordsLinked to original sources
PubMed2006

Effect of pedal rate on diurnal variations in cardiorespiratory variables.

Recently, it was observed that the freely chosen pedal rate of elite cyclists was significantly lower at 06:00 than at 18:00 h, and that ankle kinematics during cycling exhibits diurnal variation. The modification of the pedaling technique and pedal rate observed throughout the day could be brought about to limit the effect of diurnal variation on physiological variables. Imposing a pedal rate should limit the subject's possibility of adaptation and clarify the influence of time of day on physiological variables. The purpose of this study was to determine whether diurnal variation in cardiorespiratory variables depends on pedal rate. Ten male cyclists performed a submaximal 15 min exercise on a cycle ergometer (50% Wmax). Five test sessions were performed at 06:00, 10:00, 14:00, 18:00, and 22:00 h. The exercise bout was divided into three equivalent 5 min periods during which different pedal rates were imposed (70 rev x min(-1), 90 rev x min(-1) and 120 rev x min(-1)). No significant diurnal variation was observed in heart rate and oxygen consumption, whatever the pedal rate. A significant diurnal variation was observed in minute ventilation (p=0.01). In addition, the amplitude of the diurnal variation in minute ventilation depended on pedal rate: the higher the pedal rate, the greater the amplitude of its diurnal variation (p=0.03). The increase of minute ventilation throughout the day is mainly due to variation in breath frequency (p=0.01)--the diurnal variation of tidal volume (all pedal rate conditions taken together) being non-significant--but the effect of pedal rate x time of day interaction on minute ventilation specific to the higher pedal rate conditions (p=0.03) can only be explained by the increase of tidal volume throughout the day. Even though an influence of pedal rate on diurnal rhythms in overall physiological variables was not also evidenced, high pedal rate should have been imposed when diurnal variations of physiological variables in cycling were studied.

Bicycling↗
PubMed2004

Circadian rhythms in two types of anaerobic cycle leg exercise: force-velocity and 30-s Wingate tests.

Previous studies investigating the impact of circadian rhythms on performance during anaerobic cycle leg exercise have yielded conflicting results. The purpose of the present investigation was firstly, to determine the effect of the time of day on anaerobic performance during a force-velocity test on a cycle ergometer (F-V) and the Wingate test and secondly, to relate any changes in anaerobic performance to the circadian rhythm in oral temperature. Nineteen subjects volunteered to take part in the study. In a balanced and randomized study design, subjects were measured for maximal power (P (max)) (force-velocity test), peak power (P (peak)) and mean power (P (mean)) (Wingate test) on six separate occasions. These were at 02 : 00, 06 : 00, 10 : 00, 14 : 00, 18 : 00 and 22 : 00 hours on separate days. There was an interval of 28 h between two successive tests. Oral temperature and body mass were measured before each test. Body mass did not vary during the day but a significant time of day effect was observed for the oral temperature with an acrophase at 18 : 22 +/- 00 : 34 hours. A significant circadian rhythm was found for P (max) with an acrophase at 17 : 10 +/- 00 : 52 hours and an amplitude of 7 %. A time-of-day effect was significant for F (0) and V (0). Also a significant circadian rhythm was observed for P (peak) with an acrophase at 17 : 24 +/- 00 : 36 hours and an amplitude of 7.6 % and for P (mean) with an acrophase at 18 : 00 +/- 01 : 01 hours and an amplitude of 11.3 %. The results indicated that oral temperature, P (peak), P (mean) and P (max) varied concomitantly during the day. These results suggest that there was a circadian rhythm in anaerobic performance during cycle tests. The recording of oral temperature allows one to estimate the time of occurrence of maximal and minimal values in the circadian rhythm of anaerobic performance.

Adult↗
PubMed2003

Diurnal variations in cycling kinematics.

Physiological and biomechanical constraints as well as their fluctuations throughout the day must be considered when studying determinant factors in the preferred pedaling rate of elite cyclists. The aim of this study was to monitor the diurnal variation of spontaneous pedaling rate and movement kinematics over the crank cycle. Twelve male competitive cyclists performed a submaximal exercise on a cycle ergometer for 15 min at 50% of their W(max). Two test sessions were performed at 06:00 and 18:00 h on two separate days to assess diurnal variation in the study variables. For each test session, the exercise bout was divided into three equivalent 5-min periods during which subjects were requested to use different pedal rates (spontaneous cadence, 70 and 90 rev min(-1)). Pedal rate and kinematics data (instantaneous pedal velocity and angle of the ankle) were collected. The results show a higher spontaneous pedal rate in the late afternoon than in the early morning (p < 0.001). For a given pedal rate condition, there was a less variation in pedal velocity during a crank cycle in the morning than in the late afternoon. Moreover, diurnal variations were observed in ankle mobility across the crank cycle, the mean plantar flexion observed throughout the crank cycle being greater in the 18:00 h test session (p < 0.001). These results suggest that muscular activation patterns during a cyclical movement could be under the influence of circadian fluctuations.

Adult↗
PubMed2002

Circadian rhythms during cycling exercise and finger-tapping task.

The aim of this study was to follow the circadian fluctuation of the spontaneous pedal rate and the motor spontaneous tempo (MST) in a sample of highly trained cyclists. Ten subjects performed five test sessions at various times of day. During each test session, subjects were required to perform (i) a finger-tapping task, in order to set the MST and (ii) a submaximal exercise on a cycle ergometer for 15 min at 50% of their Wmax. For this exercise, pedal rate was freely chosen. Spontaneous pedal rate and heart rate (HR) were measured continuously. The results demonstrated a circadian variation for mean oral temperature, HR, and MST. Under submaximal exercise conditions, HR showed no significant time-of-day influence although spontaneous pedal rate changed significantly throughout the day. Circadian rhythm of oral temperature and pedal rate were strongly correlated. Moreover, a significant positive correlation was found between MST and pedal rate. Both parameters may be controlled by a common brain oscillator. MST, rest HR, and pedal rate changes follow the rhythm of internal temperature, which is considered to be the major marker in chronobiology, therefore, if there is a relation between MST and pedal rate, we cannot rule out partial dependence of both parameters on body temperature.

Adult↗
PubMed1997

How to measure human adaptation in extreme environments: the case of Antarctic wintering-over.

BACKGROUND: Whether wintering-over causes cognitive and sensory impairment and associated adaptation problems is still a subject of debate. Conflicting results reported in the literature may be due to the difference in the experimental tasks. Moreover, interpersonal variability can hide the effects. HYPOTHESIS: Performance on cognitive and psychomotor tasks can be an indicator of adaptation problems. METHODS: Subjects were 10 scientists and 6 technicians (both clinically normal) who wintered-over for a year in the Antarctic. A subset of tasks of the AGARD battery of Standardized Tests for Research with Environmental Stressors (SB) was completed eight times during the isolation. To assess adaptation, the adaptability questionnaire (AQ) was completed by the physician before every performance test. RESULTS: SB showed a sensitive period of adaptation at mid-winter and at the end of the isolation, but the performance in the different tasks did not deteriorate exactly at the same time. No systematic relationship between AQ notations and SB performances was noted. However, three subjects showed significant positive correlations: r > 0.8, p < 0.05 (i.e., low adaptation = low performance). CONCLUSION: Some clinically normal individuals can experience adaptation problems, and SB tasks can be an indicator of these problems when comparisons are done at an individual level.

Adaptation, Physiological↗
PubMed1989

[Stability in shooting: the effect of expertise in the biathlon and in rifle shooting].

The aim of this study is to compare the body-gun stability of biathletes and rifle shooters up to the firing of a shot, when shooting in standing position. Eight subjects are tested: two experts and two novices in rifle shooting, two experts and two novices in biathlon. Electromyographic (EMG) activity of the tibialis anterior, gastrocnemius and deltoid muscles, as well as rifle oscillation and centre-of-pressure displacements were recorded during a set of ten shots per subject. The results revealed that expert biathletes seem to use a different strategy than expert rifle shooters, each of them adapting to the characteristics of their respective discipline. No significant pattern emerged from tests with novice rifle shooters, as their scores correlated only weakly with the various parameters measured in this study.

Adult↗