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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

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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.

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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.

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Kristie-Lee Taylor, John Cronin, Nicholas D. Gill, Dale W. Chapman, and Jeremy Sheppard

Purpose:

This investigation aimed to quantify the typical variation for kinetic and kinematic variables measured during loaded jump squats.

Methods:

Thirteen professional athletes performed six maximal effort countermovement jumps on four occasions. Testing occurred over 2 d, twice per day (8 AM and 2 PM) separated by 7 d, with the same procedures replicated on each occasion. Jump height, peak power (PP), relative peak power (RPP), mean power (MP), peak velocity (PV), peak force (PF), mean force (MF), and peak rate of force development (RFD) measurements were obtained from a linear optical encoder attached to a 40 kg barbell.

Results:

A diurnal variation in performance was observed with afternoon values displaying an average increase of 1.5–5.6% for PP, RPP, MP, PV, PF, and MF when compared with morning values (effect sizes ranging from 0.2–0.5). Day to day reliability was estimated by comparing the morning trials (AM reliability) and the afternoon trials (PM reliability). In both AM and PM conditions, all variables except RFD demonstrated coefficients of variations ranging between 0.8–6.2%. However, for a number of variables (RPP, MP, PV and height), AM reliability was substantially better than PM. PF and MF were the only variables to exhibit a coefficient of variation less than the smallest worthwhile change in both conditions.

Discussion:

Results suggest that power output and associated variables exhibit a diurnal rhythm, with improved performance in the afternoon. Morning testing may be preferable when practitioners are seeking to conduct regular monitoring of an athlete’s performance due to smaller variability.

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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.

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Emma K. Zadow, James W. Fell, Cecilia M. Kitic, Jia Han, and Sam S. X. Wu

preexercise measures of T temp . To detect rhythmic variations in any exercise task, it is important that exercise tasks are reproducible. 15 Cycling TTs have been demonstrated to be highly reliable methods for monitoring cycling performance 17 and have been observed to show diurnal variations in self

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In the article by Aloui A, Chaouachi A, Chtourou H, et al, “Effects of Ramadan on the Diurnal Variations of Repeated-Sprint Performance,” in Int J Sport Physiol Perform. 8(3), p. 255, we printed two incorrect times of day. In the second paragraph under the Participants heading, “dinner between 10 and 11 PM) and sleeping habits (sleeping between 8 and 9 PM” should read “dinner between 8 and 9 PM) and sleeping habits (sleeping between 10 and 11 PM.” We apologize for the error.

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Diogo V. Leal, Lee Taylor, and John Hough

trials were completed at 12 PM to avoid the influence of diurnal variation of the hormones being examined. Participants abstained from exercise, caffeine, and alcohol intake 24 hours before each main trial. A standard breakfast chosen by the participant was consumed before 09:00 AM and was replicated

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Caoimhe Tiernan, Mark Lyons, Tom Comyns, Alan M. Nevill, and Giles Warrington

drinks consumed), or any indication of consideration for diurnal variations, 17 as the players may have woken up 30 minutes or 2 hours prior to the collection. To reduce measurement error and ensure a stringent method for examining salivary cortisol, the players’ diet before the swab, sleep quantity and

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Júlio A. Costa, João Brito, Fábio Y. Nakamura, Eduardo M. Oliveira, Ovidio P. Costa, and António N. Rebelo

, Rae et al 20 proposed comparing morning and evening time-trial performance, RPE, and mood state of trained swimmers, taking into account chronotype and habitual training time-of-day. The authors found significant diurnal variation in performance when the swimmers were grouped according to habitual