Correction: High intensity, circuit-type integrated neuromuscular training alters energy balance and reduces body mass and fat in obese women: A 10-month training-detraining randomized controlled trial.

[This corrects the article DOI: 10.1371/journal.pone.0202390.].

In-Season Integrative Neuromuscular Strength Training Improves Performance of Early-Adolescent Soccer Athletes.

Panagoulis, C, Chatzinikolaou, A, Avloniti, A, Leontsini, D, Deli, CK, Draganidis, D, Stampoulis, T, Oikonomou, T, Papanikolaou, K, Rafailakis, L, Kambas, A, Jamurtas, AZ, and Fatouros, IG. In-season integrative neuromuscular strength training improves performance of early-adolescent soccer athletes. J Strength Cond Res 34(2): 516-526, 2020-Although forms of integrative neuromuscular training (INT) are used extensively for injury prevention and treatment, no information exists about its effects on performance of adolescent athletes. We investigated the effects of an in-season INT intervention on performance of early-adolescent players using a 2-group, repeated-measures design. Twenty-eight early adolescents were randomly assigned to a control group (CG, participated only in soccer training, N = 14, 11.4 ± 0.57 years, Tanner stage 2.8 ± 0.6) or an experimental group (INT was added to conventional soccer training, N = 14, 11.2 ± 0.5 years, Tanner stage 2.6 ± 0.5). Integrative neuromuscular training (8 weeks, 3 sessions·wk) aimed to develop core strength, hamstrings eccentric strength, hip/knee musculature, and dynamic stability using body mass exercises, medicine balls, rocker boards, Bosu, stability balls, etc. Ball shooting speed, speed (10, 20-m), change of direction (COD), jumping performance, and strength were measured before and after training. A 2-way repeated-measures ANOVA was used to analyze data. Integrative neuromuscular training improved 10- and 20-m speed (2.52-2.13 and 3.61-3.39 seconds, respectively, p < 0.05), strength (40.1-44.4 kg, p < 0.05), jumping ability (squat jump: 16.3-17.9 cm; countermovement jump: 19.1-20.3 cm, p < 0.05), COD (18.0-17.3 seconds, p < 0.05), and shooting speed (73.8-79.0 km·h, p < 0.05). In the CG, soccer training caused an improvement of smaller magnitude in 10 m and shooting speed (p < 0.05), whereas COD and jumping performance remained unaffected while 20-m speed, COD, and strength deteriorated. These results indicate that an 8-week INT program may induce positive adaptations in performance of early-adolescent soccer players during in-season training, suggesting that INT may be an effective training intervention for this age group.

The Yo-Yo Intermittent Endurance Level 2 Test: Reliability of Performance Scores, Physiological Responses and Overload Characteristics in Competitive Soccer, Basketball and Volleyball Players.

The purpose of this study was to evaluate the reliability and reproducibility of the physiological and overload features of the Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2) in competitive male soccer (n = 20), basketball (n = 11), and volleyball players (n = 10). The participants completed Yo-Yo IE2 tests on three separate occasions with assessment of performance, heart rate, running speed, accelerations, decelerations and body load using GPS instrumentation. The intra-class correlation coefficient index, confidence intervals and coefficients of variation were calculated to assess the reliability of the test. Intra-class correlation coefficients for test-retest trials in the total sample ranged from large to nearly perfect (total distance: 0.896; mean speed: 0.535; maximum speed: 0.715; mean HR: 0.876; maximum HR: 0.866; body load: 0.865). The coefficients of variation for distance, mean speed, HR response, as well as acceleration and deceleration scores for test-retest trials ranged from 1.2 to 12.5% with no differences observed among particular sport disciplines. The CV for shuttles performed ranged from 4.4 to 5.5% in all sports. Similar results were obtained for the three different categories of players tested. These results suggest that the Yo-Yo IE2 test appears to be a reliable alternative for evaluating the ability to perform intermittent high-intensity running in different outdoor and indoor team sports. Players may need one or two familiarization tests to ensure valid assessment of intermittent endurance capacity. It appears that the Yo-Yo IE2 test incorporates accelerations and decelerations in a consistent and reproducible fashion.

Longitudinal determinants of 12-month changes on bone health in adolescent male athletes.

We identified the determinants of 12-month changes of areal bone mineral density (aBMD), hip geometry and trabecular bone score (TBS) in adolescent male athletes. Changes in region-specific lean mass and the type of sport are the most consistent determinants in this population. PURPOSE: This study aims to identify the determinants of 12-month changes of areal bone mineral density (aBMD), hip geometry and trabecular bone score (TBS) in adolescent male athletes. METHODS: The sample was 104 adolescent males aged 12-14 years at baseline that were followed over 12 months: 39 swimmers, 37 footballers (or soccer players) and 28 cyclists. Dual-energy X-ray absorptiometry measured aBMD at the whole body, lumbar spine and dual hip. Hip geometry estimates at the femoral neck were measured using hip structural analysis. Lumbar spine texture was measured by TBS. RESULTS: Multivariate regression models significantly explained 38-60% of the variance in the aBMD changes, 36-62% in the hip geometry estimates changes and 45% in the TBS changes. Δregion-specific lean mass was the most consistent predictor of changes in aBMD outcomes (ß = 0.591 to 0.696), followed by cycling participation (ß = - 0.233 to - 0.262), swimming participation (ß = - 0.315 to - 0.336) and ΔMVPA (ß = 0.165). Cycling participation was the most consistent predictor of changes in hip geometry estimates (ß = - 0.174 to - 0.268), followed by Δregion-specific lean mass (ß = 0.587) and Δcardiorespiratory fitness (ß = 0.253). Finally, cycling and swimming participation (ß = - 0.347 to - 0.453), Δregion-specific lean mass (ß = 0.848) and Δstature (ß = 0.720) were predictors of change in TBS. CONCLUSIONS: Changes in region-specific lean mass and the type of sport are the most consistent determinants of 12-month changes in aBMD, hip geometry estimates and TBS in adolescent male athletes. TRIAL REGISTRATION: ISRCTN17982776.

High intensity, circuit-type integrated neuromuscular training alters energy balance and reduces body mass and fat in obese women: A 10-month training-detraining randomized controlled trial.

This randomized controlled trial examined body mass, body composition, energy balance and performance responses of previously sedentary overweight/obese women to a circuit-type integrated neuromuscular training program with alternative modalities. Forty-nine healthy overweight or class I obese females (36.4±4.4 yrs) were randomly assigned to either a control (N = 21), training (N = 14) or training-detraining (N = 14) group. In weeks 1-20, the training groups trained three times/week using 10-12 whole-body exercises of progressively increased intensity/volume, organized in timed interval circuit form. In weeks 21-40, the training group continued training whereas the training-detraining group not. Heart rate, perceived exertion, blood lactate, exertion, oxygen consumption and excess post-exercise oxygen consumption were measured for one session/phase/person and exercise energy expenditure was calculated. Energy intake, habitual physical activity, resting metabolic rate, body composition, body mass, strength and maximal oxygen consumption were measured at baseline, mid-intervention and post-intervention. A two-way repeated measures ANOVA was used to determine differences between three time points and three groups. In C, VO2max declined (p<0.013) and body fat (p<0.008), waist (p<0.059) and hip (p<0.012) circumferences increased after 40 weeks compared to baseline. Training reduced body mass (6%, p<0.001), body fat (~5.5%, p<0.001) and increased fat-free mass (1.2-3.4%, p<0.05), strength (27.2%, p<0.001) and endurance (26.8%, p<0.001) after a 10-month implementation period using a metabolic overload of only 5-12 metabolic equivalents of task-hours per week. Training induced a long-term negative energy balance during an exercise and a non-exercise day due to an elevation of resting metabolic rate (6%-10%, p<0.05) and exercise-related energy expenditure. Training had an 8% and 94% attrition and attendance rates, respectively. Training-induced gains were attenuated but not lost following a 5-month detraining. A 10-month implementation of a high-intensity interval type training program elicited both endurance and musculoskeletal gains and resulted in a long-term negative energy balance that induced a progressive and sustained reduction of body and fat mass. TRIAL REGISTRATION: ClinicalTrials.gov NCT03134781.

The Trainability of Adolescent Soccer Players to Brief Periodized Complex Training.

PURPOSE: To investigate the effect of a complex, short-term strength/power training protocol on performance and body composition of elite early adolescent soccer players. METHODS: Twenty-two players (14-15 y) were randomly assigned to (1) an experimental group (N = 12; participated in a 5-wk training protocol with traditional multijoint power resistance exercises, Olympic-style lifts, plyometric drills, and speed work; 4 times per week) or (2) a control group (N = 10). Strength and power performance (jumping, speed, change of direction, repeated sprint ability, endurance, isokinetic strength of knee flexors and extensors, maximal strength in various lifts, and speed-endurance) were evaluated pretraining and posttraining. RESULTS: Cessation of training for 5 weeks in the control group induced a marked performance deterioration (∼5%-20%). Training not only prevented strength performance deterioration but also increased it (∼2%-30%). Endurance and repeated sprint ability declined to a smaller extent in experimental group compared with control group (15% vs 7.5%). Isometric strength and body composition remained unaltered in both groups. CONCLUSIONS: Results demonstrate that (1) young players exhibit a high level of trainability of their strength/power performance (but not endurance) in response to a short-term complex training protocol during early adolescence, (2) Olympic-style lifts are characterized by increased safety in this age group and appear to be highly effective, (3) lifts incorporating a hip thrust result in increased strength of both knee extensors and flexors, (4) cessation of training for only 5 weeks results in marked deterioration of strength/power and endurance performance, and (5) improvement of strength/power performance may be related to neural-based adaptation as body composition remained unaffected.

Exercise-Induced Oxidative Stress Responses in the Pediatric Population.

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.

Physical activity may be a potent regulator of bone turnover biomarkers in healthy girls during preadolescence.

This study investigated the effects of different levels of habitual physical activity (PA) assessed by pedometry on bone turnover markers of preadolescent girls according to a cross-sectional experimental design. Sixty prepubertal girls of similar chronological age, bone age, maturity level, and nutritional status were assigned to a low PA (LPA; n = 25), a moderate PA (MPA; n = 17), or a high PA (HPA; n = 18) group. Dual-energy X-ray absorptiometry was used to measure areal bone mineral density (BMD) and bone mineral content (BMC) of the lumbar spine (L2-L4) and dominant hip (femoral neck and trochanter). Blood was collected for the measurement of alkaline phosphatase (ALP), bone-specific ALP (BSAP), procollagen type I N-terminal propeptide (PINP), C-terminal telopeptide of collagen I (CTX), parathyroid hormone (PTH), osteocalcin, thyroid-stimulating hormone, estradiol, testosterone, luteinizing hormone, and follicle-stimulating hormone concentrations. ANOVA revealed that the HPA group (18,695 ± 1244 steps per day) had a lower daily energy intake and body mass than the MPA group (10,774 ± 521 steps per day) and the LPA group (7633 ± 1099 steps per day). The HPA group had higher (P < 0.05) lumbar and hip BMD and hip BMC than the LPA group and higher (P < 0.05) lumbar BMD than the MPA group. The MPA group had higher (P < 0.05) hip BMC than the LPA group. The HPA group had greater (P < 0.05) values of BSAP, PINP, and ALP and lower (P < 0.05) values of PTH and CTX than the LPA group but not the MPA group. A partial correlation analysis (adjusted for body mass index) revealed a positive correlation of steps per day with BMD and BSAP concentration and a negative correlation with PTH and CTX concentration. In conclusion, PA increases BMD and BMC of premenarcheal girls by favoring bone formation over bone resorption.

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.

Physical activity is associated with bone geometry of premenarcheal girls in a dose-dependent manner.

OBJECTIVE: To determine the relationship between habitual physical activity (PA) level and peripheral qualitative computed tomography-determined quantitative tibia characteristics of premenarcheal girls. METHODS: Premenarcheal girls matched for age (10-13 years), bone age and maturity level were assigned into: a) low PA group (LPA, n=25), b) moderate PA group (MPA, n=17), and c) high PA group (HPA, n=18). Participants' daily dietary intake, tibia's geometry and serum levels of calcium and vitamin D were assessed. RESULTS: Premenarcheal girls demonstrating HPA exhibited greater pericortical thickness, cross-sectional area (CSA) and bone mineral content (BMC) (p<.001) in cortical bone, greater BMC, volumetric bone density (vBMD) and polar stress strength index (SSIp) in trabecular bone (p<0.001-0.05) and greater total BMC (p<.05) and vBMD (p<.01) when compared to their physically inactive or moderately active counterparts. MPA exhibited greater values of cortical BMC (p<.01) and SSIp (p<.05) than LPA. Partial correlation analysis (adjusted for BMI) revealed modest associations between PA score and bone geometry parameters (r=0.36-0.49, p<.05) at 38% of tibia length. CONCLUSIONS: Habitual PA affects geometry of both cortical and trabecular areas of a long bone of premenarcheal girls in a dose-dependent manner. Specifically, PA increases both the density and size of cortical bone but only the density of trabecular bone during preadolescence. Given the importance of peak bone mass for future fracture risk, high levels of PA during childhood could be a major target for public health interventions aimed at optimising bone health in prepubertal children when the greatest bone gains occur.

Plyometrics' trainability in preadolescent soccer athletes.

Plyometric training (PT) is a widely used method to improve muscle ability to generate explosive power. This study aimed to determine whether preadolescent boys exhibit plyometric trainability or not. Forty-five children were randomly assigned to either a control (CG, N = 21, 10.6 ± 0.5 years; participated only in regular soccer practice) or a plyometric training group (PTG, N = 24, 10.6 ± 0.6 years; participated in regular soccer practice plus a plyometric exercise protocol). Both groups trained for 12 weeks during the in-season period. The PT exercises (forward hopping, lateral hopping, shuffles, skipping, ladder drills, skipping, box jumps, low-intensity depth jumps) were performed twice a week. Preadolescence was verified by measuring Tanner stages, bone age, and serum testosterone. Speed (0-10, 10-20, 20-30 m), leg muscle power (static jumping, countermovement jumping, depth jumping [DJ], standing long jump [SLJ], multiple 5-bound hopping [MB5]), leg strength (10 repetition maximum), anaerobic power (Wingate testing), and soccer-specific performance (agility, kicking distance) were measured at baseline, midtraining, and posttraining. The CG caused only a modest (1.2-1.8%) increase in speed posttraining. The PTG induced a marked (p < 0.05) improvement in all speed tests (1.9-3.1% at midtraining and 3-5% at posttraining) and vertical jump tests (10-18.5% at midtraining and 16-23% at posttraining), SLJ (2.6% at midtraining and 4.2% at posttraining), MB5 (14.6% at midtraining and 23% at posttraining), leg strength (15% at midtraining and 28% at posttraining), agility (5% at midtraining and 23% at posttraining), and kicking distance (13.6% at midtraining and 22.5% at posttraining). Anaerobic power remained unaffected in both groups. These data indicate that (a) prepubertal boys exhibit considerable plyometric trainability, and (b) when soccer practice is supplemented with a PT protocol, it leads to greater performance gains.

Elite premenarcheal rhythmic gymnasts demonstrate energy and dietary intake deficiencies during periods of intense training.

This study determined dietary intake and energy balance of elite premenarcheal rhythmic gymnasts during their preseason training. Forty rhythmic gymnasts and 40 sedentary age-matched females (10-12 yrs) participated in the study. Anthropometric profile and skeletal ages were determined. Dietary intake and physical activity were assessed to estimate daily energy intake, daily energy expenditure, and resting metabolic rate. Groups demonstrated comparable height, bone age, pubertal development, resting metabolic rate. Gymnasts had lower body mass, BMI, body fat than age-matched controls. Although groups demonstrated comparable daily energy intake, gymnasts exhibited a higher daily energy expenditure resulting in a daily energy deficit. Gymnasts also had higher carbohydrate intake but lower fat and calcium intake. Both groups were below the recommended dietary allowances for fiber, water, calcium, phosphorus and vitamin intake. Gymnasts may need to raise their daily energy intake to avoid the energy deficit during periods of intense training.

Resistance training and detraining effects on flexibility performance in the elderly are intensity-dependent.

The present investigation attempted to determine whether resistance exercise intensity affects flexibility and strength performance in the elderly following a 6-month resistance training and detraining period. Fifty-eight healthy, inactive older men (65- 78 yrs) were randomly assigned to 1 of 4 groups: a control group (C, n = 10), a low-intensity resistance training group (LI, n = 14, 40% of 1 repetition maximum [1RM]), a moderate-intensity resistance training group (MI, n = 12, 60% of 1RM), or a high-intensity resistance training group (HI, n = 14, 80% of 1RM). Subjects in exercise groups followed a 3 days per week, whole-body (10 exercises, 3 sets per exercise) protocol for 24 weeks. Training was immediately followed by a 24-week detraining period. Strength (bench and leg press 1RM) and range of motion in trunk, elbow, knee, shoulder, and hip joints were measured at baseline and during training and detraining. Resistance training increased upper- (34% in LI, 48% in MI, and 75% in HI) and lower-body strength (38% in LI, 53% in MI, and 63% in HI) in an intensity-dependent manner. Flexibility demonstrated an intensity-dependent enhancement (3-12% in LI, 6-22% in MI, and 8-28% in HI). Detraining caused significant losses in strength (70-98% in LI, 44-50% in MI, and 27-29% in HI) and flexibility (90-110% in LI, 30-71% in MI, and 23-51% in HI) in an intensity-dependent manner. Results indicate that resistance training by itself improves flexibility in the aged. However, intensities greater than 60% of 1RM are more effective in producing flexibility gains, and strength improvement with resistance training is also intensity-dependent. Detraining seems to reverse training strength and flexibility gains in the elderly in an intensity-dependent manner.