Ralf Roth

A school-based physical activity program to improve health and fitness in children aged 6-13 years ("Kinder-Sportstudie KISS"): study design of a randomized controlled trial (ISRCTN15360785)

BackgroundChildhood obesity is the result of a long lasting imbalance between energy intake and energy expenditure. A major contributing factor is physical inactivity which is closely linked to bone health, cardiovascular disease risk, fitness and psychological factors. The school seems to provide an excellent setting to enhance levels of physical activity (PA). However, there is insufficient data from previous school-based intervention trials on how to enhance overall PA. It is also unknown whether an intervention aimed at increasing PA is effective in improving the childrens health. The purpose of this paper is to outline the design of a school-based randomized, controlled trial (RCT) aiming to increase overall PA and to improve fitness and health in 6- to 13-year-old children.Methods/Design15 schools were randomized to the intervention (n = 9) or the control (n = 6) group, stratified by geographic region (urban vs. rural) and by age (1st and 5th grade). Participation was given for all children in the intervention group since in this group the intervention was part of the normal school curriculum. The intervention during one academic year consisted of: 1. two additional physical education classes per week given by trained physical education teachers adding up to a total of five PA classes per week, 2. short PA breaks (2–5 min each) during academic lessons, 3. PA home work, and 4. adaptation of recreational areas around the school. All children underwent anthropometric measurements, blood pressure assessment, fitness testing, measurement of PA and they filled out questionnaires. At least 70% of all children agreed to blood sampling and measurements of body composition and bone mineral measurements by dual energy x-ray absorptiometry. The primary endpoints of the study after one year were an increase in total PA by accelerometry, an increase in aerobic fitness measured by the 20 m shuttle run, a decrease in percent body fat derived from skinfold measurements and an increase in quality of life as assessed by the child health questionnaire in the intervention group compared to the control group. Secondary outcomes were overall fitness, differences in body composition including body fat distribution, cardiovascular risk factors, psychosocial health, bone mineral content and density of femur, lumbar spine and total body and food intake.DiscussionOur preliminary data suggest that the children were representative of Swiss children with respect to sex, socio-demographic status, and body mass index. Short-term results can be expected by the beginning of 2007. We hypothesized that our intervention will lead to an increase in PA, fitness and overall health. Based on our data, we aim to provide important information regarding the influence of such an intervention on these outcome measures in school-aged children and to provide nationwide guidelines to improve PA in children.

Contribution of physical education to overall physical activity

For many children, physical activity (PA) during physical education (PE) lessons provides an important opportunity for being physically active. Although PA during PE has been shown to be low, little is known about the contribution of PA during PE to overall PA. The aim was therefore to assess childrens PA during PE and to determine the contribution of PE to overall PA with special focus on overweight children. Accelerometer measurements were done in 676 children (9.3 ± 2.1 years) over 4–7 days in 59 randomly selected classes. Moderate‐and‐vigorous PA (MVPA; ≥ 2000 counts/min) during PE (MVPAPE), overall MVPA per day (MVPADAY), and a comparison of days with and without PE were calculated by a regression model with gender, grade, and weight status (normal vs overweight) as fixed factors and class as a random factor. Children spent 32.8 ± 15.1% of PE time in MVPA. Weight status was not associated to MVPAPE. MVPAPE accounted for 16.8 ± 8.5% of MVPADAY, and 17.5 ± 8.2% in overweight children. All children were more active on days with PE than on days without PE (differences: 16.1 ± 29.0 min of MVPADAY; P ≤ 0.001; 13.7 ± 28.0 min for overweight children). Although MVPAPE was low, PE played a considerable role in providing PA and was not compensated by reducing extracurricular MVPA.

Slackline training for balance and strength promotion.

The prevalence of sustaining a sport injury is high in adults. Deficits in postural control/muscle strength represent important injury-risk factors. Thus, the purpose of this study was to investigate the impact of a specific type of balance training, i. e. slackline training, followed by detraining on balance and strength performance. Twenty-seven adults participated in this study and were assigned to an intervention (age 22.8±3.3 yrs) or a control group (age 23.9±4.4 yrs). The intervention group participated in 4 weeks of slackline training on nylon webbings. Detraining lasted 4 weeks. Tests included the measurement of (A) total centre of pressure displacements during one-legged standing on a balance platform and during the compensation of a perturbation impulse, (B) maximal torque and rate of force development (RFD) of the plantar flexors on an isokinetic device, and (C) jumping height on a force platform. After training, no significant interaction effects were observed for variables of static/dynamic postural control, maximal torque, and jumping height. Training-induced improvements were found for RFD. After the withdrawal of the training stimulus, RFD slightly decreased. Given that the promotion of balance and strength is important for injury prevention, changes in RFD only might not be sufficient to produce an injury-preventive effect.

Estimation of percentage body fat in 6- to 13-year-old children by skinfold thickness, body mass index and waist circumference

We evaluated the accuracy of skinfold thicknesses, BMI and waist circumference for the prediction of percentage body fat (PBF) in a representative sample of 372 Swiss children aged 6-13 years. PBF was measured using dual-energy X-ray absorptiometry. On the basis of a preliminary bootstrap selection of predictors, seven regression models were evaluated. All models included sex, age and pubertal stage plus one of the following predictors: (1) log-transformed triceps skinfold (logTSF); (2) logTSF and waist circumference; (3) log-transformed sum of triceps and subscapular skinfolds (logSF2); (4) log-transformed sum of triceps, biceps, subscapular and supra-iliac skinfolds (logSF4); (5) BMI; (6) waist circumference; (7) BMI and waist circumference. The adjusted determination coefficient (R² adj) and the root mean squared error (RMSE; kg) were calculated for each model. LogSF4 (R² adj 0.85; RMSE 2.35) and logSF2 (R² adj 0.82; RMSE 2.54) were similarly accurate at predicting PBF and superior to logTSF (R² adj 0.75; RMSE 3.02), logTSF combined with waist circumference (R² adj 0.78; RMSE 2.85), BMI (R² adj 0.62; RMSE 3.73), waist circumference (R² adj 0.58; RMSE 3.89), and BMI combined with waist circumference (R² adj 0.63; RMSE 3.66) (P < 0.001 for all values of R² adj). The finding that logSF4 was only modestly superior to logSF2 and that logTSF was better than BMI and waist circumference at predicting PBF has important implications for paediatric epidemiological studies aimed at disentangling the effect of body fat on health outcomes.

Reliability of gait parameters during treadmill walking in community-dwelling healthy seniors.

The present study aimed at assessing the between- and within-day-variability of temporal and spatial gait characteristics during treadmill walking in community-dwelling seniors. In 20 active, healthy seniors (10 women, 10 men, age: 64.8 (SD 3.2) years, height: 1.70 (0.10) m, weight: 69.7 (10.9) kg, physical activity: 11 (6) h week(-1)) gait characteristics were assessed on three days in weekly intervals (between-day variability). Either on days two or three, testing was repeated 30 min after the initial trial (within-day variability). We determined routine spatio-temporal gait parameters as well as gait variability during 400 steps at a normal walking speed (5.0 (0.4) km h(-1)) on a one-dimensional ground reaction force measuring treadmill. No significant mean differences occurred in any parameter for between- and within-day comparisons. Between-day ICC were high (ICC≥0.86) for most parameters except for temporal (ICC=0.44) and spatial (ICC=0.22) gait variability. Coefficients of variation (CoV) were also high in the latter parameters (CoV=30.2-36.1%), whereas all other variables showed clearly lower values (CoV<7%). CoV were still lower between days 2 and 3 (CoV<5%). Compared to between-day comparisons, within-day variability was comparable in spatio-temporal gait parameters (CoV<5%, ICC≥0.97) and lower in gait variability parameters (CoV<18%, ICC≥0.72-0.74). In conclusion, most gait parameters were highly reliable during treadmill walking. Changes of less than 10% can be detected with sufficient confidence. Gait variability parameters were less reliable and, thus, should be carefully interpreted.

Effects of slackline training on balance, jump performance & muscle activity in young children.

The study investigated the effects of slackline training (rope balancing) on balance, jump performance and muscle activity in children. Two primary-school classes (intervention, n=21, INT: age: 10.1 (SD 0.4) y, weight: 33.1 (4.5) kg; control, n=13, CON: age: 10.0 (SD 0.4) y, weight: 34.7 (7.4) kg) participated. Training was performed within 6 weeks, 5 times per week for 10 min each day. Balance (static and dynamic stance), countermovement jumps, reverse balancing on beams (3, 4.5 and 6 cm width), slackline standing (single- and double-limb) and electromyographic activity (soleus, gastrocnemius, tibialis anterior) were examined. INT significantly improved single- and double-limb slackline standing (double limb: 5.1 (3.4) s-17.2 (14.4) s; right leg: 8.2 (5.8) s-38.3 (36.0) s; left leg: 10.6 (5.8) s-49.0 (56.3) s; p<0.001; 0.17<ηp²<0.22). Reduced left-leg dynamic sway (-20.8%, p=0.06, ηp²=0.10), improved 4.5 cm balancing (+18.5%, p=0.08, ηp²=0.10) and decreased muscle activity during slackline standing for the mm. soleus (-23%, p=0.10, ηp²=0.18) and tibialis anterior (-26%, p=0.15, ηp²=0.14) was observed for INT. Jump performance remained unchanged (p=0.28, ηp²=0.04). In conclusion, daily slackline training results in large slackline-specific balance improvements. Transfer effects to static and dynamic stance, reverse balancing or jumping performance seemed to be restricted.

Effects of a Salsa Dance Training on Balance and Strength Performance in Older Adults

Background: Deficits in static and particularly dynamic postural control and force production have frequently been associated with an increased risk of falling in older adults. Objective: The objectives of this study were to investigate the effects of salsa dancing on measures of static/dynamic postural control and leg extensor power in seniors. Methods: Twenty-eight healthy older adults were randomly assigned to an intervention group (INT, n = 14, age 71.6 ± 5.3 years) to conduct an 8-week progressive salsa dancing programme or a control group (CON, n = 14, age 68.9 ± 4.7 years). Static postural control was measured during one-legged stance on a balance platform and dynamic postural control was obtained while walking on an instrumented walkway. Leg extensor power was assessed during a countermovement jump on a force plate. Results: Programme compliance was excellent with participants of the INT group completing 92.5% of the dancing sessions. A tendency towards an improvement in the selected measures of static postural control was observed in the INT group as compared to the CON group. Significant group × test interactions were found for stride velocity, length and time. Post hoc analyses revealed significant increases in stride velocity and length, and concomitant decreases in stride time. However, salsa dancing did not have significant effects on various measures of gait variability and leg extensor power. Conclusion: Salsa proved to be a safe and feasible exercise programme for older adults accompanied with a high adherence rate. Age-related deficits in measures of static and particularly dynamic postural control can be mitigated by salsa dancing in older adults. High physical activity and fitness/mobility levels of our participants could be responsible for the nonsignificant findings in gait variability and leg extensor power.

Combined strength and power training in high-level amateur football during the competitive season: a randomised-controlled trial.

Abstract We aimed to analyse the effects of combined strength and power training during the competitive season on physical fitness in high-level amateur football players. Sixteen male players (22.5 (SD 2.5) years, 1.79 (0.05) m, 76.8 (6.1) kg) from one team were randomly assigned to either a strength training (ST, N = 8) or a control (CON, N = 8) group. ST conducted lower extremity resistance exercises combined with plyometrics and/or sprints 2 × 30 min per week for 7 weeks. CON performed technical-tactical training during the same time period. Before and after training several physical fitness parameters were assessed: one-repetition maximum (1-RM, half squat), isometric peak strength and rate of force development (RFD, leg press), jump height (countermovement, CMJ, drop jump, DJ), sprint times, agility, and intermittent endurance. Large significant test × group interactions were found for 1-RM, CMJ, and DJ reactivity index with increases in CT relative to CON(+11 to 18%). Although not significant (P < 0.20), likely practically relevant effects were observed for isometric peak strength and RFD (+24 to 29%). We found no relevant interaction effects for agility, sprint times, and intermittent endurance. A 7-week in-season combined strength and power training program can improve relevant strength and jump parameters in high-level amateur football players.

INTRA AND INTERSESSION RELIABILITY OF BALANCE MEASURES DURING ONE-LEG STANDING IN YOUNG ADULTS

Muehlbauer, T, Roth, R, Mueller, S, and Granacher, U. Intra and intersession reliability of balance measures during one-leg standing in young adults. J Strength Cond Res 25(8): 2228-2234, 2011—A study was designed to investigate the intra and intersession reliability during 1-leg standing recorded from a computerized balance platform. Thirty-nine healthy young men (n = 17, age range: 20-30 years) and women (n = 22, age range: 21-28 years) performed 3 testing sessions, with the second session 30 minutes (intrasession comparison) and the third session 1 week (intersession comparison) after the initial testing session. Within each testing session, participants completed 3 trials of 1-leg standing with their dominant leg. Reliability statistics were calculated using the mean of all 3 trials during each session for 6 balance measures (i.e., total displacements of the center of pressure [CoP], the CoP displacements in mediolateral and anterior-posterior directions, and the CoP speed and CoP area and their SD). Test-retest reliability was examined calculating both, intraclass correlation coefficient (ICC) with 95% confidence interval (95% CI) and Bland-Altman plots. In both sexes and irrespective of balance measure, ICC values were ≥0.75 except for 1 parameter in men. This indicates an excellent intra and intersession reliability. Bland-Altman plots confirmed these findings by showing that only 1 or 2 (4.5-11.8%) of the data points were beyond the 95% CI. Practitioners and clinicians are provided with a posturographic test setup that proved to be reliable. Researchers can use these data to identify the range in which the true value of a subjects score lies and estimate a priori sample sizes.

Testing single and double limb standing balance performance: Comparison of COP path length evaluation between two devices

Center of pressure (COP) path length evaluation was commonly applied to measure postural sway and usually obtained from gold standard force plates. Thus, we comparatively investigated the feasible and less-expensive GKS® balance system (GKS) with the Kistler® force platform (KIS). 34 non-specifically trained but active adults (14 males, 20 females, age: 25.4±4.8 years; weight: 69.3±12.3 kg; height: 1.75±0.09 m, sports activity: 5.8±3.6 hours per week) were randomly tested on both devices during double and single limb stance with opened and closed eyes. Irrespective of the analysed time frame, repeated measures analyses of variances revealed higher path length readings for GKS compared to KIS for 30 s (F=6.8, p=0.01) and 10 s (F=21.2, p=0.001). Large effect sizes of the COP path length differences between GKS and KIS decreased from easy tasks (double limb, eyes open; d(30-s)=2.55, d(10-s)=2.04) to the most severe task (single limb, eyes closed; d(30-s)=0.02, d(10-s)=0.23). According to Bland and Altman, the limits of agreements indicated a high random variability component (between 29%, double limb, eyes open and 67%, single limb, eyes closed). The overall intraclass correlation coefficients (ICC) across all four standing balance tasks were moderate for the 30 s- (0.57) as well as the 10 s-analysis (0.65). In conclusion, the COP path length displacements obtained from the GKS balance system seem to differ with a considerable random variability from Kistler force platform data. Thus, measurements of the evaluated devices should not be used interchangeably. Further methodological investigations regarding balance measures seem warranted.