Exercise-induced oxidative stress responses in the pediatric population

This is the final version of the article. Available from the publisher via the DOI in this record.Adults demonstrate an upregulation of their pro- and anti-oxidant mechanisms in response to acute exercise while systematic exercise training enhances their antioxidant capacity, thereby leading to a reduced generation of free radicals both at rest and in response to exercise stress. However, less information exists regarding oxidative stress responses and the underlying mechanisms in the pediatric population. Evidence suggests that exercise-induced redox perturbations may be valuable in order to monitor exercise-induced inflammatory responses and as such training overload in children and adolescents as well as monitor optimal growth and development. The purpose of this review was to provide an update on oxidative stress responses to acute and chronic exercise in youth. It has been documented that acute exercise induces age-specific transient alterations in both oxidant and antioxidant markers in children and adolescents. However, these responses seem to be affected by factors such as training phase, training load, fitness level, mode of exercise etc. In relation to chronic adaptation, the role of training on oxidative stress adaptation has not been adequately investigated. The two studies performed so far indicate that children and adolescents exhibit positive adaptations of their antioxidant system, as adults do. More studies are needed in order to shed light on oxidative stress and antioxidant responses, following acute exercise and training adaptations in youth. Available evidence suggests that small amounts of oxidative stress may be necessary for growth whereas the transition to adolescence from childhood may promote maturation of pro- and anti-oxidant mechanisms. Available evidence also suggests that obesity may negatively affect basal and exercise-related antioxidant responses in the peripubertal period during pre- and early-puberty

Determinants of bone outcomes in adolescent athletes at baseline: the PRO-BONE study

This is the author accepted manuscript. The final version is available from the American College of Sports Medicine (ACSM) via the DOI in this record.Purpose: The determinants of areal bone mineral density (aBMD) and hip geometry 26 estimates in adolescent athletes are poorly understood. This study aimed to identify the 27 determinants of aBMD and hip geometry estimates in adolescent male athletes. Methods: 28 One hundred twenty one males (13.1±0.1 years) were measured: 41 swimmers, 37 29 footballers, 29 cyclists and 14 controls. Dual energy X-ray absorptiometry (DXA) measured 30 aBMD at lumbar spine, femoral neck (FN) and total body. Hip structural analysis evaluated 31 hip geometry estimates at the FN. Multiple linear regression examined the contribution of the 32 sports practised, stature, lean and fat mass, serum calcium and vitamin D, moderate to 33 vigorous physical activity (MVPA), vertical jump and cardiorespiratory fitness (CRF) with 34 aBMD and hip geometry estimates. Results: Region specific lean mass was the strongest 35 positive predictor of aBMD (β = 0.614 - 0.931) and football participation was the next 36 strongest predictor (β = 0.304 - 0.579). Stature (β = 0.235 - 0.380), fat mass (β = 0.189), 37 serum calcium (β = 0.103), serum vitamin D (β = 0.104 - 0.139) and vertical jump (β = 0.146 38 - 0.203) were associated with aBMD across various specific sites. All hip geometry estimates 39 were associated with lean mass (β = 0.370 - 0.568) and stature (β = 0.338 - 0.430). Football 40 participation was associated with hip cross-sectional area (β = 0.322) and MVPA (β = 0.140 - 41 0.142). CRF (β = 0.183 - 0.207) was associated with section modulus and cross-sectional 42 moment of inertia. Conclusions: Region specific lean mass is the strongest determinant of 43 aBMD and hip geometry estimates in adolescent male athletes. Football participation and 44 stature were important determinants for aBMD and hip geometry estimates while the 45 contribution of the other predictors was site specific.The research leading to these results has received funding from the European Union Seventh Framework Programme ([FP7/2007-2013] under grant agreement n°. PCIG13-GA-2013-61849

Adipose Tissue Lipolysis Is Upregulated in Lean and Obese Men During Acute Resistance Exercise

OBJECTIVE—To investigate the effect of acute resistance exercise on adipose tissue triacylglycerol lipase activity (TGLA) in lean and obese men

Recovery kinetics of knee flexor and extensor strength after a football match

© 2015 The Authors. Published by PLOS. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1371/journal.pone.0128072We examined the temporal changes of isokinetic strength performance of knee flexor (KF) and extensor (KE) strength after a football match. Players were randomly assigned to a control (N = 14, participated only in measurements and practices) or an experimental group (N = 20, participated also in a football match). Participants trained daily during the two days after the match. Match and training overload was monitored with GPS devices. Venous blood was sampled and muscle damage was assessed pre-match, post-match and at 12h, 36h and 60h post-match. Isometric strength as well as eccentric and concentric peak torque of knee flexors and extensors in both limbs (dominant and non-dominant) were measured on an isokinetic dynamometer at baseline and at 12h, 36h and 60h after the match. Functional (KFecc/KEcon) and conventional (KFcon/KEcon) ratios were then calculated. Only eccentric peak torque of knee flexors declined at 60h after the match in the control group. In the experimental group: a) isometric strength of knee extensors and knee flexors declined (P<0.05) at 12h (both limbs) and 36h (dominant limb only), b) eccentric and concentric peak torque of knee extensors and flexors declined (P<0.05) in both limbs for 36h at 60°/s and for 60h at 180°/s with eccentric peak torque of knee flexors demonstrating a greater (P<0.05) reduction than concentric peak torque, c) strength deterioration was greater (P<0.05) at 180°/s and in dominant limb, d) the functional ratio was more sensitive to match-induced fatigue demonstrating a more prolonged decline. Discriminant and regression analysis revealed that strength deterioration and recovery may be related to the amount of eccentric actions performed during the match and athletes' football-specific conditioning. Our data suggest that recovery kinetics of knee flexor and extensor strength after a football match demonstrate strength, limb and velocity specificity and may depend on match physical overload and players' physical conditioning level.Published versio

Ex-post Performance Implications of Divergence of Managers’ Perceptions of ‘Distance’ From ‘Reality’ in International Business

Despite much research on “distance”, little attention has been paid to the effect of divergence of managers’ perceptions of distance from reality (i.e. distance divergence) and its implications for firm performance. This knowledge is highly important since managerial perceptions of the firm’s environment do not always coincide with the actual environmental characteristics. Consequently, strategies based on inaccurate data may result in erroneous forecasts, missed opportunities and business failure. Using survey data from senior managers of Swedish exporters and corresponding objective data, this study is a first attempt to explore the ex-post performance implications of “distance divergence” when expanding into foreign markets. Our results demonstrate that the larger the divergence between managers’ perceptions of cultural distance and corresponding “objective” distance, the lower the performance expressed in companies’ sales. However, over/underestimation of cultural distance does not have differential effects on firm performance.“Stiftelsen Olle Hakelius Stipendiefond”, Grant no: 1165001

The effects of static stretching on speed and agility: One or multiple repetition protocols?

Although static stretching (SS) is utilized during warm-up before training and competition, the results about its effects on performance remain controversial. We examined whether performing a stretch of short-to-moderate duration (<60 sec) in a single repetition produces a similar or different effect on speed and agility performance from the effect which is produced while performing the same stretch in multiple repetitions of the same total duration. According to a repeated measurement design, 40 trained males were randomly assigned to either (1) a single repetition group or (2) a multiple repetition group. The participants in each group performed five trials: a control trial (no stretches were performed) and four experimental trials of SS protocols consisting of five exercises performed at either 20 sec (2 × 10 in the second group), 30 sec (3 × 10 in the second group), 40 sec (4 × 10 in the second group) or 60 sec (6 × 10 in the second group) of total duration. A two-way repeated measures analysis of variance showed that the participants in both group improved their speed performance in response to the 20-sec trial, whereas agility remained unaffected. Data analysis also revealed that the repetition number did not affect speed and agility performance. These data suggest that SS of short duration (<30 sec) may actually improve acute speed performance, whereas SS of moderate duration may not hamper speed and agility performance. Moreover, the effects of SS protocols are related to the total duration of each exercise and not to the number of repetitions in which each exercise is performed

The effects of static stretching on speed and agility: One or multiple repetition protocols?

Although static stretching (SS) is utilized during warm-up before training and competition, the results about its effects on performance remain controversial. We examined whether performing a stretch of short-to-moderate duration (<60 sec) in a single repetition produces a similar or different effect on speed and agility performance from the effect which is produced while performing the same stretch in multiple repetitions of the same total duration. According to a repeated measurement design, 40 trained males were randomly assigned to either (1) a single repetition group or (2) a multiple repetition group. The participants in each group performed five trials: a control trial (no stretches were performed) and four experimental trials of SS protocols consisting of five exercises performed at either 20 sec (2 × 10 in the second group), 30 sec (3 × 10 in the second group), 40 sec (4 × 10 in the second group) or 60 sec (6 × 10 in the second group) of total duration. A two-way repeated measures analysis of variance showed that the participants in both group improved their speed performance in response to the 20-sec trial, whereas agility remained unaffected. Data analysis also revealed that the repetition number did not affect speed and agility performance. These data suggest that SS of short duration (<30 sec) may actually improve acute speed performance, whereas SS of moderate duration may not hamper speed and agility performance. Moreover, the effects of SS protocols are related to the total duration of each exercise and not to the number of repetitions in which each exercise is performed

The acute effects of static stretching on speed and agility performance depend on stretch duration and conditioning level

Avloniti, A, Chatzinikolaou, A, Fatouros, IG, Avloniti, C, Protopapa, M, Draganidis, D, Stampoulis, T, Leontsini, D, Mavropalias, G, Gounelas, G, and Kambas, A. The acute effects of static stretching on speed and agility performance depend on stretch duration and conditioning level. J Strength Cond Res 30(10): 2767–2773, 2016—Although static stretching (SS) is an integral part of physical preparation before training and competition, its usefulness in regards to power performance improvement has been questioned. The aim of this study was to investigate the effect of 6 SS durations on speed and agility performance. According to a cross-over design, 34 trained men (age, 20.5 ± 1.4 years; height, 1.81 ± 0.2 m; weight, 77.2 ± 2.6 kg; body fat, 8.2 ± 2.6%) participated in a control session (no stretch) and 6 experimental conditions (10, 15, 20, 30, 40, and 60 seconds) performed in a randomized order. Performance in speed (10 and 20 m) and agility (T-test) was measured after the control and experimental conditions. Static stretching, consisting of stretches for hip extensors, hip adductors, knee extensors, knee flexors, and ankle sole flexors, was performed after light cardiovascular exercise (8 minutes). A 1-way repeated-measures analysis of variance showed that speed was improved only by SS of short duration (15/20 seconds), whereas agility remained unaffected by all SS trials. When participants' speed and agility level was taken into account, it was revealed that only those of moderate performance demonstrated an improved speed (in 15- and 20-second trials) and agility (in 10- and 15-second trials) performance. These results suggest that short-duration SS protocols induce an acute improvement of speed and agility performance, whereas longer-duration SS protocols have neither positive nor negative effect. Furthermore, it seems that individuals of lower speed and agility performance level are more likely to benefit by a short-duration SS protocol

The Motor-Proficiency-Test for children between 4 and 6 years of age (MOT 4-6): An investigation of its suitability in Greece

Given the negative influence of motor difficulties on people&apos;s quality of life their early identification seems to be crucial and consequently the information provided by a sound assessment tool is of great importance. The aim of this study was to examine the suitability of the MOT 4-6 (Zimmer &amp; Volkamer, 1987) for use with preschoolers in Greece. Seven hundred and seventy-eight Greek children aged 48-71 months participated in the study. The two-way ANOVA used on total MOT performance revealed significant differences among the age groups formed in preschool age within Greeks, while boys&apos; and girls&apos; scores were quite similar. From the comparisons of Greeks&apos; scores with the German standardization sample&apos;s ones, statistically significant differences were found in two age groups. However according to the Cohen&apos;s d effect size they were not of great importance. The distribution of Greeks&apos; scores according to the test cut-offs, revealed that the MOT can differentiate all levels of performance, although a slight deviation from the distribution of Germans&apos; scores was noticed. Finally, both the test-retest reliability and internal consistency of the test were found to be excellent. The MOT 4-6 seems to be a valuable motor assessment tool for Greek preschoolers. Regarding its norms, despite the minor differences that were noticed between the motor development of Greek and German preschoolers, their adjustment was thought to be unnecessary. Instead of lowering the norms, efforts for preventing the motor performance decline should be enhanced. © 2012 Elsevier Ltd