Jacques Larue

Effects of regular training at the same time of day on diurnal fluctuations in muscular performance

The aim of this study was to determine whether there is an effect of time of day on the adaptation to strength training at maximal effort. Fourteen participants took part in this experiment. Their peak anaerobic power (Wingate anaerobic test) and peak knee extension torque at six angular velocities (1.05, 2.10, 3.14, 4.19, 5.24 and 6.29 rad · s -1 ) were recorded in the morning (between 07:00 and 08:00 h) and in the evening (between 17:00 and 18:00 h) just before and 2 weeks after a 6 week course of regular training. Seven of them trained only in the morning and seven only in the evening. Multivariate analysis of variance revealed a significant group 2 pre-/post-training 2 time of day interaction effect for peak torque and peak anaerobic power. Before training, in both groups, peak torque and peak anaerobic power were significantly higher in the evening than in the morning. After training, there was no significant difference in peak torque and peak anaerobic power between the morning and the evening for the morning training group. In contrast, in the evening training group, peak torque and peak anaerobic power were higher in the evening than in the morning. As a result of training, both peak torque and peak anaerobic power increased from their initial values as expected. The morning training group improved their peak anaerobic power significantly in the morning and in the evening, the absolute increase being larger in the morning than in the evening. The evening training group did not improve their peak anaerobic power in the morning, whereas it improved significantly in the evening. Although peak torque was significantly improved by training in the morning and evening in both groups, the absolute increase was greater in the morning than in the evening in the morning training group, whereas the opposite was the case for the evening training group. These results suggest that training twice a week at a specific hour increases the peak torque and the peak anaerobic power specifically at this hour and demonstrates that there is a temporal specificity to strength training.

Relation between sport and spatial imagery: comparison of three groups of participants.

The literature suggests that sport may be considered a spatial activity and that engaging in spatial activities increases the capacity of an individual to implement mental imagery. Moreover, mental rotation calls upon motor processes that are heavily involved in sporting activities. For these reasons, the authors hypothesized that athletes ought to perform mental rotation tasks better than nonathletes. Also, athletes trained to react quickly to constantly changing environments should be faster at processing the information in a mental rotation task than athletes operating in more settled environments. The results of this study show that athletes performed the mental rotation task significantly faster than nonathletes. These results support the suggestion that there is a link between sport and the ability to perform mental image transformations; however, this ability may not be specific to the conditions in which the athlete performs.

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.

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 Wmax. 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.

Relation between Sport Activity and Mental Rotation: Comparison of Three Groups of Subjects

The aim was to observe the relation between sport activity and performance on a mental image-transformation task. A classical mental rotation task using abstract stimuli was administered to three groups: (a) gymnasts who used mental and physical rotations in their practice, (b) athletes whose activities required very little motor rotation, and (c) nonathletes. Both sport groups performed similarly and obtained significantly shorter response times than those of the nonathletes. We suggest that the regular practice of spatial activities, such as sports, could be related to the spatial capacities of the participants.

Physical exercise and time of day: Influences on spontaneous motor tempo

To identify whether spontaneous motor rhythm is influenced by external or internal events and whether this rhythm fluctuates across the day in parallel with heart rate diurnal variations, we simultaneously recorded heart rate and spontaneous motor rate before and after a pedaling task performed five times a day by 10 healthy human subjects. Each subject performed a Spontaneous Motor Tempo, i.e., a finger-tapping task, at a comfortable and spontaneous cadence. Pre- and postexercise Spontaneous Motor Tempo was measured as well as heart rate. There were diurnal variations in Spontaneous Motor Tempo. Both measures increased significantly after pedaling, suggesting that cardiac and spontaneous rhythms are influenced simultaneously after a moderate exercise. Also, finger-taps occurred most frequently around the initiation of the heart systole. These results suggest that a putative internal clock might regulate Spontaneous Motor Tempo and that cardiac rhythm might influence this tempo

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 subjects 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 · min−1, 90 rev · min−1 and 120 rev · 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×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.

Effects of apnea on motor and cardiac rhythms.

Usually, spontaneous rhythm of movements is studied through tasks involving an increase in heart rate (HR) such as physical exercises, locomotion or mental tasks. This experiment, instead, checks whether spontaneous rhythm is influenced by HR deceleration provoked by a voluntary apnea. The performances in a motor spontaneous tempo (MST) task performed for 3 min were compared to the same finger-tapping task performed in apnea. The results show a systematic adjustment period at the beginning of each trial in order to achieve a stable MST. More interestingly, HR and MST decreased simultaneously during apnea conditions and the finger-taps occur most frequently around the ventricular systole. Assuming that apnea increases arousal level, this parallelism between cardiac and motor rhythms is in contradiction with the sympathetic hypothesis that suggested that MST is mainly influenced by arousal.