Dimitris Vlachopoulos

High intensity interval exercise is an effective alternative to moderate intensity exercise for improving glucose tolerance and insulin sensitivity in adolescent boys

OBJECTIVES High-intensity interval exercise (HIIE) may offer a time efficient means to improve health outcomes compared to moderate-intensity exercise (MIE). This study examined the acute effect of HIIE compared to a work-matched bout of MIE on glucose tolerance, insulin sensitivity (IS), resting fat oxidation and exercise enjoyment in adolescent boys. DESIGN Within-measures design with counterbalanced experimental conditions. METHODS Nine boys (14.2 ± 0.4 years) completed three conditions on separate days in a counterbalanced order: (1) HIIE; (2) work matched MIE, both on a cycle ergometer; and (3) rest (CON). An oral glucose tolerance test (OGTT) was performed after exercise or rest and the area under curve (AUC) responses for plasma [glucose] and [insulin] were calculated, and IS estimated (Cederholm index). Energy expenditure and fat oxidation were measured following the OGTT using indirect calorimetry. Exercise enjoyment was assessed using the Physical Activity Enjoyment Scale. RESULTS The incremental AUC (iAUC) for plasma [glucose] was reduced following both MIE (-23.9%, P = 0.013, effect size [ES] = -0.64) and HIIE (-28.9%, P=0.008, ES = -0.84) compared to CON. The iAUC for plasma [insulin] was lower for HIIE (-24.2%, P = 0.021, ES = -0.71) and MIE (-29.1%, P = 0.012, ES = -0.79) compared to CON. IS increased by 11.2% after HIIE (P = 0.03, ES = 0.76) and 8.4% after MIE (P = 0.10, ES = 0.58). There was a trend for an increase in fat oxidation following HIIE (P = 0.097, ES = 0.70). Both HIIE and MIE were rated as equally enjoyable (P > 0.05, ES < 0.01). CONCLUSION A single bout of time efficient HIIE is an effective alternative to MIE for improving glucose tolerance and IS in adolescent boys immediately after exercise.

The Impact of Sport Participation on Bone Mass and Geometry in Male Adolescents.

Purpose Exercise is an effective approach for developing bone mass and adolescence is a key period to optimize bone health. However, sports-specific training may have different effects on bone outcomes. This study examined the differences on bone outcomes between osteogenic (football) and nonosteogenic (swimming and cycling) sports and a control group in male adolescents. Methods One hundred twenty one males (13.1 ± 0.1 yr) were measured: 41 swimmers, 37 footballers, 29 cyclists, and 14 controls. Dual energy X-ray absorptiometry measured bone mineral density (BMD) and bone mineral content at lumbar spine, right and left hip, and total body. Hip Structural Analysis evaluated bone geometry at the femoral neck. Quantitative ultrasound evaluated bone stiffness at both feet. Results Footballers had significantly higher BMD at total body less head (7%–9%), total hip (12%–21%), and legs (7%–11%) compared with all groups and significantly higher BMD at the femoral neck than controls (14%). Cyclists had higher BMD at the trochanter (10%) and bone mineral content at the arms (10%) compared with controls. Geometrical analysis showed that footballers had significantly higher cross-sectional area (8%–19%) compared with all groups, cross-sectional moment of inertia (17%) compared with controls and section modulus compared with cyclists (11%) and controls (21%). Footballers had significantly higher bone stiffness compared with all groups (10%–20%) at the dominant foot and (12%–13%) at the nondominant foot compared with swimmers and controls. Conclusions Adolescent male footballers exhibited higher bone density, geometry, and stiffness compared with swimmers, cyclists and controls. Although swimmers and cyclists had higher bone outcomes compared with controls, these differences were not significant.

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.

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

Purpose The determinants of areal bone mineral density (aBMD) and hip geometry estimates in adolescent athletes are poorly understood. This study aimed to identify the determinants of aBMD and hip geometry estimates in adolescent male athletes. Methods One hundred twenty-one men (13.1 ± 0.1 yr) were measured: 41 swimmers, 37 footballers, 29 cyclists, and 14 controls. Dual energy X-ray absorptiometry measured aBMD at lumbar spine, femoral neck and total body. Hip structural analysis evaluated hip geometry estimates at the femoral neck. Multiple linear regression examined the contribution of the sports practised, stature, lean and fat mass, serum calcium and vitamin D, moderate to vigorous physical activity, vertical jump and cardiorespiratory fitness with aBMD and hip geometry estimates. Results Region-specific lean mass was the strongest positive predictor of aBMD (&bgr; = 0.614–0.931) and football participation was the next strongest predictor (&bgr; = 0.304–0.579). Stature (&bgr; = 0.235–0.380), fat mass (&bgr; = 0.189), serum calcium (&bgr; = 0.103), serum vitamin D (&bgr; = 0.104–0.139), and vertical jump (&bgr; = 0.146–0.203) were associated with aBMD across various specific sites. All hip geometry estimates were associated with lean mass (&bgr; = 0.370 - 0.568) and stature (&bgr; = 0.338–0.430). Football participation was associated with hip cross-sectional area (&bgr; = 0.322) and moderate to vigorous physical activity (&bgr; = 0.140–0.142). Cardiorespiratory fitness (&bgr; = 0.183–0.207) was associated with section modulus and cross-sectional moment of inertia. Conclusions Region-specific lean mass is the strongest determinant of aBMD and hip geometry estimates in adolescent male athletes. Football participation and stature were important determinants for aBMD and hip geometry estimates, whereas the contribution of the other predictors was site specific.

Longitudinal Adaptations of Bone Mass, Geometry, and Metabolism in Adolescent Male Athletes: The PRO‐BONE Study

Adolescence is a crucial period for bone development, and exercise can enhance bone acquisition during this period of life. However, it is not known how the different loading sports practiced can affect bone acquisition in adolescent male athletes. Therefore, the purpose of the present study was to determine the 1‐year longitudinal bone acquisition among adolescent males involved in osteogenic (football) and non‐osteogenic (swimming and cycling) sports and to compare with active controls. A total of 116 adolescent males aged 12 to 14 years at baseline were followed for 1 year: 37 swimmers, 37 footballers, 28 cyclists, and 14 active controls. Bone mineral content (BMC) was assessed using dual‐energy X‐ray absorptiometry (DXA); cross‐sectional area (CSA), cross‐sectional moment of inertia (CSMI), and section modulus (Z) at the femoral neck was assessed using hip structural analysis (HSA); and bone texture of the lumbar spine was assessed using trabecular bone score (TBS). Serum N‐terminal propeptide of procollagen type I (PINP), isomer of the Carboxi‐terminal telopeptide of type 1 collagen (CTX‐I), total serum calcium, and 25 hydroxyvitamin D [25(OH)D] were analyzed. Footballers had significantly higher adjusted BMC at the lumbar spine (7.0%) and femoral neck (5.0%) compared with cyclists, and significantly greater BMC at the lumbar spine (6.9%) compared with swimmers. Footballers presented significantly greater TBS (4.3%) compared with swimmers, and greater CSMI (10.2%), CSA (7.1%), Z (8.9%) and TBS (4.2%) compared with cyclists. No differences were noted between cyclists and swimmers, both groups had similar bone acquisition compared with controls. PINP was significantly higher in footballers and controls compared with cyclists and swimmers (3.3% to 6.0%), and 25(OH)D was significantly higher in footballers and cyclists compared with swimmers and controls (9.9% to 13.1%). These findings suggest that bone acquisition is higher in adolescent male footballers compared with swimmers and cyclists at the femoral neck and lumbar spine sites of the skeleton.

Agreement Between Standard Body Composition Methods to Estimate Percentage of Body Fat in Young Male Athletes

PURPOSE To examine the intermethods agreement of dual-energy X-ray absorptiometry (DXA) and foot-to-foot bioelectrical impedance analysis (BIA) to assess the percentage of body fat (%BF) in young male athletes using air-displacement plethysmography (ADP) as the reference method. METHODS Standard measurement protocols were carried out in 104 athletes (40 swimmers, 37 footballers, and 27 cyclists, aged 12-14 y). RESULTS Age-adjusted %BF ADP and %BF BIA were significantly higher in swimmers than footballers. ADP correlates better with DXA than with BIA (r = .84 vs r = .60, P < .001). %BF was lower when measured by DXA and BIA than ADP (P < .001), and the bias was higher when comparing ADP versus BIA than ADP versus DXA. The intraclass correlation coefficients between DXA and ADP showed a good to excellent agreement (r = .67-.79), though it was poor when BIA was compared with ADP (r = .26-.49). The ranges of agreement were wider when comparing BIA with ADP than DXA with ADP. CONCLUSION DXA and BIA seem to underestimate %BF in young male athletes compared with ADP. Furthermore, the bias significantly increases with %BF in the BIA measurements. At the individual level, BIA and DXA do not seem to predict %BF precisely compared with ADP in young athletic populations.

Body composition, nutritional profile and muscular fitness affect bone health in a sample of schoolchildren from Colombia: The fuprecol study

The objective of the present study is to investigate the relationships between body composition, nutritional profile, muscular fitness (MF) and bone health in a sample of children and adolescents from Colombia. Participants included 1118 children and adolescents (54.6% girls). Calcaneal broadband ultrasound attenuation (c-BUA) was obtained as a marker of bone health. Body composition (fat mass and lean mass) was assessed using bioelectrical impedance analysis. Furthermore height, weight, waist circumference and Tanner stage were measured and body mass index (BMI) was calculated. Standing long-jump (SLJ) and isometric handgrip dynamometry were used respectively as indicators of lower and upper body muscular fitness. A muscular index score was also computed by summing up the standardised values of both SLJ and handgrip strength. Dietary intake and degree of adherence to the Mediterranean diet were assessed by a 7-day recall questionnaire for food frequency and the Kidmed questionnaire. Poor bone health was considered using a z-score cut off of ≤−1.5 standard deviation. Once the results were adjusted for age and Tanner stage, the predisposing factors of having a c-BUA z-score ≤−1.5 standard deviation included being underweight or obese, having an unhealthy lean mass, having an unhealthy fat mass, SLJ performance, handgrip performance, and unhealthy muscular index score. In conclusion, body composition (fat mass and lean body mass) and MF both influenced bone health in a sample of children and adolescents from Colombia. Thus promoting strength adaptation and preservation in Colombian youth will help to improve bone health, an important protective factor against osteoporosis in later life.

The effect of 12-month participation in osteogenic and non-osteogenic sports on bone development in adolescent male athletes. The PRO-BONE study

OBJECTIVES Research investigating the longitudinal effects of the most popular sports on bone development in adolescent males is scarce. The aim is to investigate the effect of 12-month participation in osteogenic and non-osteogenic sports on bone development. DESIGN A 12-month study was conducted in adolescent males involved in football, swimming and cycling and compared with an active control group. METHODS 116 adolescent males (13.1±0.1years at baseline): 37 footballers, 37 swimmers, 28 cyclists and 14 active controls were followed for 12 months. Bone mineral content (BMC) was measured by dual-energy X-ray absorptiometry, and bone stiffness was measured by quantitative ultrasound. Bone outcomes at 12 months were adjusted for baseline bone status, age, height, lean mass and moderate to vigorous physical activity. RESULTS Footballers had higher improvement in adjusted BMC at the total body, total hip, shaft, Wards triangle, legs and bone stiffness compared to cyclists (6.3-8.0%). Footballers had significantly higher adjusted BMC at total body, shaft and legs compared to swimmers (5.4-5.6%). There was no significant difference between swimmers and cyclists for any bone outcomes. Swimming and cycling participation resulted in non-significant lower bone development at most sites of the skeleton compared to controls (-4.3 to -0.6%). CONCLUSIONS Football participation induces significantly greater improvements in BMC and bone stiffness over 12 months compared to cycling and swimming. CLINICAL TRIAL REGISTRATION ISRCTN17982776.

Lean mass explains the association between muscular fitness and bone outcomes in 13-year-old boys

This study investigated the associations between fitness indices and bone outcomes in young males.

A 9-month Jumping Intervention to Improve Bone Acquisition in Adolescent Male Athletes: The PRO-BONE Study

This is the author acepted manuscript. The final version is available via the DOI in this record