Search Results

You are looking at 1 - 10 of 69 items for :

Clear All
Restricted access

Francisco J. Amaro-Gahete, Lucas Jurado-Fasoli, Alejandro R. Triviño, Guillermo Sanchez-Delgado, Alejandro De-la-O, Jørn W. Helge and Jonatan R. Ruiz

percentage at ventilatory threshold 2 (VT2), and running economy are considered important outcomes in endurance sports performance. 5 , 6 Endurance sport performance, specifically running and cycling performance, seems to present diurnal variation, being higher in the afternoon than in the morning. 7 This

Restricted access

Ignacio Perez-Pozuelo, Thomas White, Kate Westgate, Katrien Wijndaele, Nicholas J. Wareham and Soren Brage

Silva et al noted age and sex differences in three Brazilian birth cohorts from Pelotas assessed at the ages 6, 18, and 30 years of age ( da Silva et al., 2014 ), and Doherty et al described the unique diurnal patterns of physical activity by age group, documenting that the lower activity levels

Restricted access

Jennifer L.J. Heaney, Douglas Carroll and Anna C. Phillips

The present study examined the relationship between habitual physical activity, life events stress, the diurnal rhythms of cortisol and DHEA, and the cortisol:dehydroepiandrosterone (DHEA) ratio in older adults. Thirty-six participants aged ≥ 65 reported their habitual physical activity, and indicated if a particular event happened to them in the past year (stress incidence) and how stressful they perceived the event to be (stress severity). Older adults with higher stress severity demonstrated a significantly higher cortisol:DHEA ratio. Individuals with higher stress incidence scores and who did not participate in aerobic exercise had a significantly higher cortisol:DHEA ratio and flatter DHEA diurnal rhythm compared with those who regularly participated in aerobic exercise. In conclusion, life events stress may have a negative impact on the cortisol:DHEA ratio in older adults. Under conditions of high stress exposure, exercise may protect older adults from an increased cortisol:DHEA ratio and flatter DHEA diurnal rhythm.

Restricted access

David Diggin, Ross Anderson and Andrew J. Harrison

Evidence suggests reports describing the reliability of leg-spring (kleg) and joint stiffness (kjoint) measures are contaminated by artifacts originating from digital filtering procedures. In addition, the intraday reliability of kleg and kjoint requires investigation. This study examined the effects of experimental procedures on the inter- and intraday reliability of kleg and kjoint. Thirty-two participants completed 2 trials of single-legged hopping at 1.5, 2.2, and 3.0 Hz at the same time of day across 3 days. On the final test day a fourth experimental bout took place 6 hours before or after participants’ typical testing time. Kinematic and kinetic data were collected throughout. Stiffness was calculated using models of kleg and kjoint. Classifications of measurement agreement were established using thresholds for absolute and relative reliability statistics. Results illustrated that kleg and kankle exhibited strong agreement. In contrast, kknee and khip demonstrated weak-to-moderate consistency. Results suggest limits in kjoint reliability persist despite employment of appropriate filtering procedures. Furthermore, diurnal fluctuations in lower-limb muscle-tendon stiffness exhibit little effect on intraday reliability. The present findings support the existence of kleg as an attractor state during hopping, achieved through fluctuations in kjoint variables. Limits to kjoint reliability appear to represent biological function rather than measurement artifact.

Restricted access

Asma Aloui, Anis Chaouachi, Hamdi Chtourou, Del P. Wong, Monoem Haddad, Karim Chamari and Nizar Souissi

Purpose:

This study examined the effects of Ramadan on cycling repeated-sprint ability (RSA) and corresponding diurnal variations.

Methods:

Twelve active men performed an RSA test (5 × 6-s maximal sprints interspersed with 24 s passive recovery) during morning and afternoon sessions 1 wk before Ramadan (BR), during the second (R2) and the fourth (R4) weeks of Ramadan, and 2 wk after Ramadan (AR). Maximal voluntary contraction was assessed before (MVCpre), immediately after (MVCpost), and 5 min after the RSA test (MVCpost5). Moreover, hematocrit, hemoglobin, and plasma sodium and potassium (K+) concentrations were measured at rest and after the RSA test and MVCpost.

Results:

Overall, peak power (Ppeak) during the RSA test decreased throughout the 5 sprints. Ppeak measured in the first sprint and MVCpre were lower during Ramadan than BR in the afternoon (P < .05) and higher in the afternoon than the morning BR and AR (P < .05). However, this diurnal rhythmicity was not found for the last 4 sprints’ Ppeak, MVCpost, and MVCpost5 in all testing periods. Furthermore, the last 4 sprints’ Ppeak, MVCpost, MVCpost5, and morning MVCpre were not affected by Ramadan. [K+] measured at rest and after the RSA test and MVCpost were higher during Ramadan than BR in the afternoon (P < .05) and higher in the afternoon than the morning during Ramadan (P < .05).

Conclusions:

Fatigability is higher in the afternoon during Ramadan, and, therefore, training and competition should be scheduled at the time of day when physical performance is less affected.

Restricted access

Edith Filaire, Alain Massart, Jiewen Hua and Christine Le Scanff

Purpose:

The aims of study were to examine the eating behaviors among 26 professional female tennis players and to assess the diurnal patterns of stress hormones through the measurement of awakening and diurnal profiles of salivary alpha-amylase (sAA) and cortisol concentrations.

Methods:

Eating behaviors were assessed through three questionnaires (Eating Attitudes Test-26; Eating Disorders Inventory 2; and Body Shape Questionnaire), food intake by a 7-day diet record, and menstrual status by questionnaire. Perceived stress scale and anxiety state were also evaluated. Saliva samples were collected at awakening, 30 min, 60 min, and 12 hr post awakening after 6-days’ rest.

Results:

Forty-six percent of tennis players presented Disordered Eating attitudes (DE) (n = 12) with a lower body mass index, and higher state anxiety as compared with the group without DE. No differences in the Perceived Stress Scale scores were noted. Mean energy intake, protein and carbohydrates intakes were lower (p > .05) in the DE group as compared with the group without DE. Although in both groups, sAA concentrations presented a decrease in the first 30 min after awakening, and then progressively rose toward the afternoon, DE players exhibited reduced concentrations of the sAA with a decrease in its overall day secretion. Moreover, they showed a higher overall day secretion of salivary cortisol and a higher Cortisol Awakening Response.

Conclusions:

These results suggest that the activity of the sympathetic nervous system is impaired whereas the cortisol awakening response is enhanced. The long-term consequences of these modifications on health remain to be elucidated.

Restricted access

Hichem Souissi, Hamdi Chtourou, Anis Chaouachi, Mohamed Dogui, Karim Chamari, Nizar Souissi and Mohamed Amri

The aim of this study was to assess the effect of time-of-day-specific training on the diurnal variations of short-term performances in boys. Twenty-four boys were randomized into a morning-training-group (07:00–08:00h; MTG), an evening training-group (17:00–18:00h; ETG) and a control-group (CG). They performed four tests of strength and power (unilateral isometric maximal voluntary contraction of the knee extensor muscles, Squat-Jump, Counter-Movement-Jump and Wingate tests) at 07:00 and 17:00h just before (T0) and after 6 weeks of resistance training (T1). In T0, the results revealed that short-term performances improved and oral temperature increased significantly from morning to afternoon (amplitudes between 2.36 and 17.5% for both oral temperature and performances) for all subjects. In T1, the diurnal variations of performances were blunted in the MTG and persisted in the ETG and CG. Moreover, the training program increase muscle strength and power especially after training in the morning hours and the magnitude of gains was greater at the time-of-day-specific training than at other times. In conclusion, these results suggest that time-of-day-specific training increases the child’s anaerobic performances specifically at this time-of-day. Moreover, the improvement of these performances was greater after morning than evening training.

Restricted access

Douglas Potter and Denis Keeling

The effects of exercise and circadian rhythms on memory function were explored in a group of shift workers (mean age 32 yrs). A variant of the Auditory-Verbal Learning Test was used to test memory for word lists at 9:30 a.m. and 12:30, 3:30, and 6:30 p.m. in a repeated-measures design. Without exercise there was clear evidence of a circadian rhythm in memory performance, with peak performance occurring at 12:30 and poorest performance at 3:30. A brisk 10-min walk followed by a 15- to 30-min recovery period resulted in significant improvement in memory recall at all time periods except 12:30. The results of the AVLT task suggest an improvement in both working memory and long-term memory performance. Rhythmic changes in serotonin, epinephrine, norepinephrine, and acetylcholine levels all affect cortical arousal and cognitive function. Exercise may have resulted in altered levels of these neurotransmitters, increased glucose, oxygen, or nutrient levels, or from temporary changes in growth hormone or brain-derived neurotropic factor levels resulting in increased synaptogenesis and neurogenesis. The physiological basis of this temporary improvement in memory remains to be determined, but this simple behavioral intervention may have widespread application in improving memory function in all sections of the population including children and the elderly.

Restricted access

Louise Martin, Alan M. Nevill and Kevin G. Thompson

Purpose:

Fast swim times in morning rounds are essential to ensure qualification in evening finals. A significant time-of-day effect in swimming performance has consistently been observed, although physical activity early in the day has been postulated to reduce this effect. The aim of this study was to compare intradaily variation in race-pace performance of swimmers routinely undertaking morning and evening training (MEG) with those routinely undertaking evening training only (EOG).

Methods:

Each group consisted of 8 swimmers (mean ± SD: age = 15.2 ± 1.0 and 15.4 ± 1.4 y, 200-m freestyle time 132.8 ± 8.4 and 136.3 ± 9.1 s) who completed morning and evening trials in a randomized order with 48 h in between on 2 separate occasions. Oral temperature, heart rate, and blood lactate were assessed at rest, after a warm-up, after a 150-m race-pace swim, and after a 100-m time trial. Stroke rate, stroke count, and time were recorded for each length of the 150-m and 100-m swims.

Results:

Both training groups recorded significantly slower morning 100-m performances (MEG = +1.7 s, EOG = +1.4 s; P < .05) along with persistently lower morning temperatures that on average were –0.47°C and –0.60°C, respectively (P < .05). No differences were found in blood-lactate, heart-rate, and stroke-count responses (P > .05). All results were found to be reproducible (P > .05).

Conclusions:

The long-term use of morning training does not appear to significantly reduce intradaily variation in race-pace swimming or body temperature.

Restricted access

Juan Tortosa-Martínez, Angela Clow, Nuria Caus-Pertegaz, Gloria González-Caballero, Immaculada Abellán-Miralles and María José Saenz

Regular physical activity is protective against, and beneficial for, mild cognitive impairment (MCI), dementia, and Alzheimer’s disease. The mechanisms underlying these benefits remain unknown although it has been suggested that exercise-induced changes in the circadian pattern of cortisol secretion may be implicated. Fitness, salivary cortisol levels (0 and 30 min postawakening, midday, 5 p.m., and 9 p.m.), and cognitive function were determined in a group of amnestic MCI patients (n = 39) before and after a three-month exercise program (n = 19) or usual care (n = 20). At baseline, fitness measures were positively correlated with peak levels of cortisol and a greater fall in cortisol concentration from peak levels to midday. The exercise intervention successfully increased fitness and resulted in a greater fall in cortisol concentration from peak to midday, compared with the control group. The exercise intervention enhanced indices of executive function, although memory, mood, and functionality were not affected.