Objectively assessed recess physical activity in girls and boys from high and low socioeconomic backgrounds

Background

The school environment influences children’s opportunities for physical activity participation. The aim of the present study was to assess objectively measured school recess physical activity in children from high and low socioeconomic backgrounds.

Methods

Four hundred and seven children (6–11 years old) from 4 primary schools located in high socioeconomic status (high-SES) and low socioeconomic status (low-SES) areas participated in the study. Children’s physical activity was measured using accelerometry during morning and afternoon recess during a 4-day school week. The percentage of time spent in light, moderate, vigorous, very high and in moderate- to very high-intensity physical activity were calculated using age-dependent cut-points. Sedentary time was defined as 100 counts per minute.

Results

Boys were significantly (p < 0.001) more active than girls. No difference in sedentary time between socioeconomic backgrounds was observed. The low-SES group spent significantly more time in light (p < 0.001) and very high (p < 0.05) intensity physical activity compared to the high-SES group. High-SES boys and girls spent significantly more time in moderate (p < 0.001 and p < 0.05, respectively) and vigorous (p < 0.001) physical activity than low-SES boys.

Conclusions

Differences were observed in recess physical activity levels according to socioeconomic background and sex. These results indicate that recess interventions should target children in low-SES schools.

Effects of a playground marking intervention on school recess physical activity in French children

OBJECTIVE

Playground interventions offer an opportunity to enhance school recess physical activity. We aimed to assess the effects of playground marking on objectively measured school recess physical activity in French children.

METHODS

Participants were four hundred and twenty children (6-11years old) from 4 primary schools in Nord-Pas de Calais, France. Children's physical activity (PA) was measured with a uniaxial accelerometer twice a day (morning and afternoon recess) during a 4-day school week in April and May 2009. Two experimental schools (EG) received a recess-based intervention (playground markings) and two others served as controls (CG). Percentage of time spent on the following intensities of physical activity during school recess was measured before and after intervention: sedentary (SED), light physical activity (LPA), moderate physical activity (MPA), vigorous physical activity (VPA), very high physical activity (VHPA) and moderate-to-vigorous physical activity (MVPA).

RESULTS

At baseline, school recess PA among children from CG was significantly (p<0.001) higher than that among EG children. No interaction was observed between the recess-based intervention and gender. After the intervention, the EG spent significantly (p<0.05) more time in MPA, VPA and MVPA with a concomitant significant decrease in SED (p<0.05) compared to baseline, while the PA in CG remained unchanged.

CONCLUSION

Painted playground markings had a positive short-term effect on school recess physical activity levels.

Is there any relationship between physical activity level and patterns, and physical performance in children?

Background

It is often assumed that physical activity (PA) and physical performance during childhood and adolescence are beneficial for health during adulthood, but a positive relationship between PA and physical performance has not been precisely clarified in children. The lack or the weakness of the relationships between PA and physical performance could be due to the measure of PA. If the use of accelerometry is considered as an objective and common measure of PA, the real patterns of children's habitual PA must be reflected. The aim of this study was to investigate the relationship between the levels and patterns of PA assessed with high frequency accelerometry and physical performance in young children.

Methods

Eighty-six boys and 101 girls aged 6-12 years participated in this study. Physical activity was measured over a 7-day period, using a 5-s epoch. Physical performance was assessed by means of EUROFIT tests (anthropometrics, standing broad jump, the 10 × 5 meter shuttle run, the sit-and-reach, the handgrip, the number of sit-ups in 30 seconds, the 20-meter shuttle run).

Results

No relationship was found between PA and physical performance. In boys only, body fatness was negatively associated with vigorous PA (r = -0.38, p < 0.001) and very high PA (r = -0.35, p < 0.01), in contrast to light PA (r = 0.28, p < 0.01), which was positively related to body fatness.

Conclusion

In 6- to- 12 year- old children, the more active children were not the fittest. Our results also underline the need for uniformity in approach to measurement of PA, body composition and health-related fitness between studies.

Continuous vs. interval aerobic training in 8- to 11-year-old children

The aim of the present study was to show if the use of continuous-running training vs. intermittent-running training has comparable or distinct impact on aerobic fitness in children. At first, children were matched according to their chronological age, their biological age (secondary sexual stages), and their physical activity or training status. Then, after randomization 3 groups were composed. Sixty-three children (X 9.6 +/- 1.0 years) were divided into an intermittent-running training group (ITG, 11 girls and 11 boys), a continuous-running training group (CTG, 10 girls and 12 boys), and a control group (CG, 10 girls and 9 boys). Over 7 weeks, ITG and CTG participated in 3 running sessions per week. Before and after the training period, they underwent a maximal graded test to determine peak oxygen uptake (peak VO2) and maximal aerobic velocity (MAV). Intermittent training consisted of short intermittent runs with repeated exercise and recovery sequences lasting from 5/15 to 30/30 seconds. With respect to continuous training sessions, repeated exercise sequences lasted from 6' to 20'. Training-effect threshold for statistical significance was set at p < 0.05. After training, peak VO2 was significantly improved in CTG (+7%, p < 0.001) and ITG (+4.8%, p < 0.001), whereas no difference occurred for the CG (-1.5%). Similarly, MAV increased significantly (p < 0.001) in both CTG (+8.7%) and ITG (+6.4%) with no significant change for CG. Our results demonstrated that both continuous and intermittent-running sessions induced significant increase in peak VO2 and MAV. Therefore, when adequate combinations of intensity/duration exercises are offered to prepubertal children, many modalities of exercises can successfully be used to increase their aerobic fitness. Aerobic running training is often made up of regular and long-distance running exercises at moderate velocity, which causes sometimes boredom in young children. During the developmental years, it seems therefore worthwhile to use various training modalities, to make this activity more attractive and thus create conditions for progress and enhanced motivation.

Lower-limb and whole-body tissue composition assessment in healthy active older women

AIM

The study evaluated, in active elderly women, the accuracy and bias of anthropometry and bioelectrical impedance analysis (BIA) for lower-limb and whole-body tissue composition measures using dual-energy X-ray absorptiometry (DXA) as the criterion method.

METHODS

Nineteen individuals (66.1 +/- 4.2 years) participated in the study. Whole-body fat mass (FM) and fat-free mass (FFM) were measured by anthropometry, BIA and DXA. Lower-limb volume (LLV) and lower-limb FFM (LLFFM) were assessed by anthropometry and DXA.

RESULTS

LLV and LLFFM were significantly overestimated by anthropometry vs. DXA (p < 0.05 and p < 0.001, respectively) but significant relationships were observed [coefficient of determination (R(2)) > 0.25, p < 0.05]. No significant difference was observed between FM(A) (where (A) stands for anthropometry) vs. FM(DXA) and FFM(A) vs. FFM(DXA) and significant relationships were observed [R(2) = 0.93, p < 0.001, coefficient of variation (CV) = 7.3%; and R(2) = 0.85, p < 0.001, CV = 4.4%, respectively]. No significant difference was observed between FM(BIA) and FM(DXA) and a significant relationship was observed (R(2) = 0.80, p < 0.001, CV = 11.6%). FFM was significantly underestimated by BIA vs. DXA (p < 0.01).

CONCLUSIONS

In active elderly women, (i) compared with DXA, anthropometry overestimates LLV and LLFFM; (ii) anthropometry can be an accurate method for assessing whole-body composition; and (iii) despite a non-significant bias for the FM measurement, the BIA tends to overestimate FM and underestimate FFM.

Squat jump performance during growth in both sexes: comparison with cycling power

The purpose of this cross-sectional study was to investigate leg muscle power and compare two activities (jumping and cycling) in 383 girls and 407 boys ages 9-19 years. Results in anthropometric characteristics and jumping performance were comparable until midadolescence, and sex differences were observed. Lean leg volume (LLV) was the reason for most of the variance (76% in girls and 88% in boys) in jumping performance. However the LLV exponent was higher than expected in boys but not girls. Therefore, unidentified qualitative changes of muscle function during growth in boys must be considered. The squat jump index (SJI) was highly correlated to cycling peak power (CPP; N = 790, r = .94, p < .001). Although prediction error of CPP from SJI was less than 5% when considering each sex-and-age group, individual errors mounted to 40%. Due to its practicability, SJI is recommended in large-scale developmental prospective studies. However, cycling and jumping protocols are not interchangeable when measuring peak power values.

Psychoendocrine and physical performance responses in male Tunisian rugby players during an international competitive season

The aim was to investigate a follow-up study based on hormonal, physical, and psychological parameters among rugby players who trained during a whole season interspersed with competitions on an international level. Fitness or reciprocally tiredness as well as competitive anxiety were evaluated, respectively, using the French Society for Sports Medicine (SFMS) and the sport competition anxiety test (SCAT) questionnaires. In this study, SFMS and SCAT scores increased respectively over the competitive season. The SFMS score revealed a state of relative tiredness at the end of the season, highlighted by a slight decrement in physical performances. The SCAT score changes are related to the competition context and therefore increased accordingly to the importance of the competition stake. We analyzed the corticotrope and the gonadotrope axis before (T(1)), and at the end of the national and international rugby season (T(2)). Training did not affect the resting salivary cortisol (Csal) levels, but induced a decrease in resting testosterone (Tsal) values, resulting in a dropped T/C ratio. Competition, in both periods (T(1)-T(2)), provoked a significant increase in Csal levels, but the Tsal responses depended on the match stake. Their concentrations increased when the competition generated an important stress and decreased when the psychological conditions remained relatively stable. SFMS is preferentially correlated with resting Csal levels and T/C values measured at 08:00 hr but not with Tsal. SCAT is highly correlated with competitive Csal and Tsal concentrations measured before and after the matches.

High-Intensity Intermittent Cycle Ergometer Exercise: Effect of Recovery Duration and Resistive Force Selection on Performance

The purpose of this study was to compare the exercise performance and postexercise recovery of 8 male subjects using four different maximal high-intensity intermittent cycle ergometry protocols. Resistive forces were calculated by multiplying fat-free mass (FFM) or total-body mass (TBM) by 0.75 g.kg(-1). Rest periods between successive sprints were 30 s (R30) or 60 s (R60) duration. Higher pedal velocities were recorded using FFM as opposed to TBM (P<0.05). Rest intervals of R60 (P<0.05) influenced the peak power output values (903.88 +/- 184.01 W; TBM/R30 vs. 852.98 +/- 209.68 W; FFM/R30 vs. 965.64 +/- 177.48 W; TBM/R60 vs. 968.66 +/- 173.70 W; FFM/R60). Diastolic blood pressure (DBP) was lower than resting values (P < 0.05) postexercise in all protocols. These findings demonstrate that power outputs rely on resistive force selection and recovery duration, and that high-intensity exercise may provide an alternative to aerobic activity in the management of hypertension.

Improving physical activity assessment in prepubertal children with high-frequency accelerometry monitoring: a methodological issue

OBJECTIVE

The aim of this study was to examine the duration of physical activity (PA) bouts in prepubertal children with high-frequency accelerometry monitoring.

METHODS

Thirteen boys and thirteen girls (aged 8-10 years) from one school in North of France had their PA recorded during 7 days using a uniaxial Actigraph accelerometer. To examine PA behavior patterns, the epoch was set at 2 s. Times spent in light (LPA), moderate (MPA), vigorous (VPA) and very high (VHPA) intensity activity and the daily number of PA bouts of different durations (from 2 to 1200 s) were calculated for each intensity level. Data were collected in 2004.

RESULTS

The mean duration of PA bouts was 70.8+/-13.2 s for LPA, 9.0+/-2.8 s for MPA, 4.7+/-1.2 s for VPA and 3.9+/-1.6 s for VHPA. For the whole population, 80% of MPA, 93% of VPA and 96% of VHPA lasted less than 10 s. Although times spent in VPA and VHPA represented 2.4% of the total PA time, VPA and VHPA bouts accounted for 36.1+/-5.8% of the total amount of PA.

CONCLUSION

Children's PA pattern is highly transitory and intermittent whatever its intensity. Physical activity assessed with a sampling interval related to children's behavior may improve our understanding of their PA patterns.

Anaerobic Fitness Tests: What Are We Measuring?

Anaerobic fitness, during growth and development, has not received the same attention from researchers as aerobic fitness. This is surprising given the level of anaerobic energy used daily during childhood and adolescence. During physical activity and sport, the child is spontaneously more attracted to short-burst movements than to long-term activities. It is, however, well known that in anaerobic activities such as sprint cycling, sprint running or sprint swimming, the child's performance is distinctly poorer than that of the adult. This partly reflects the child's lesser ability to generate mechanical energy from chemical energy sources during short-term high-intensity work or exercise. Direct measurements of the rate or capacity of anaerobic pathways for energy turnover presents several ethical and methodological difficulties. Therefore, rather than measure energy supply, pediatric exercise scientists have concentrated on measuring short-term power output by means of standardized protocol tests such as short-term cycling power tests, running tests or vertical jump tests. There is, however, no perfect test and, therefore, it is important to acknowledge the benefits and limitations of each testing method. Mass-related short-term power output was shown to increase dramatically during growth and development, whereas the corresponding increase in peak blood lactate was considerably lower. This suggests that the observed difference between children and adolescents during short-term power output testing may be related to neuromuscular factors, hormonal factors and improved motor coordination.

Upper Body Contribution During Leg Cycling Peak Power in Teenage Boys and Girls

This study investigated gender differences in upper-body contribution to cycle muscle power in 23 adolescents. All subjects performed two 5-s and one 20-s cycling sprint, using two protocols: with handgrip (WG) and without handgrip (WOG). Maximal handgrip strength was assessed for each individual. Absolute peak and mean cycling power was corrected for total fat-free mass (FFM) and for lean leg volume (LLV). Males showed higher cycling performance than females. Peak power and 20-s mean power (flywheel inertia included), but not optimal velocity, were higher WG than WOG. Especially for peak power, absolute differences between both protocols were higher in males than in females, and were significantly related to handgrip strength. The significant contribution of the upper body suggested that, for standardisation of cycle muscle power, total FFM is a more relevant variable compared with LLV. Furthermore, in adolescents, the higher contribution of the upper body musculature in males partly explained gender differences in peak power.

Critical velocity during continuous and intermittent exercises in children

The purpose of this study was to apply the "critical velocity" concept to short intermittent high-intensity running exercises in prepubescent girls and boys and to compare the running performances obtained either by intermittent or continuous exercise runs. Eleven 8 to 11-year-old children underwent a maximal graded field test to determine peak oxygen uptake (peakVO2) and maximal aerobic velocity (MAV). During the six following sessions, they randomly performed three continuous runs (90, 100, and 110% of MAV) and three intermittent runs (120, 130, and 140% of MAV) until exhaustion. Intermittent exercises consisted of repeated 15 s runs each one separated by a 15 s passive recovery interval. For continuous as well as intermittent exercises, distance versus time to exhaustion (TTE) relationships were calculated to determine continuous (CVc) and intermittent (CVi) critical velocities. Values for peakVO2 and MAV were 45.8 +/- 5.3 ml x kg(-1) x min(-1) and 10.5 +/- 1.0 km h(-1), respectively. For the whole population, a significant relationship was found between the distance to exhaustion (DTE) and TTE for continuous (r2= 0.99, P < 0.05) and intermittent exercises (r2 = 0.99, P < 0.05). Significant relationships were found between peakVO2 and both CVc (r2= 0.60, P < 0.01) and CVi (r2= 0.47, P < 0.05). In conclusion, as for continuous exercises, a linear relationship was found between DTE and TTE for short high-intensity intermittent exercises. CVc was significantly related to peakVO2, while a significant lower relationship was found between peakVO2 and CVi.

Short-term peak power changes in adolescents of similar anthropometric characteristics

PURPOSE

The present study was undertaken to examine changes of cycling peak power (P(max)), optimal pedaling frequency (Vopt), and optimal pedaling force (Fopt) with age in subjects with the same lean leg volume (LLV), leg length (LL), and percentage body fat (%BF).

METHOD

A total of 132 males aged 9.5-16.5 volunteered for this study. The population was divided into prepubertal (G1), pubertal (G2), and postpubertal (G3) groups. Within G1, G2, and G3, although the subjects were divided into three different age subgroups, there were no significant differences for LLV, %BF, and LL.

RESULTS

Results showed that within G1, G2, and G3, P(max) increased significantly with age. Optimal velocity (Vopt) increased significantly with age in G1, whereas optimal force (Fopt) increased significantly with age into the other groups (G2 and G3).

CONCLUSION

This study demonstrated that when anthropometric characteristics were controlled (LLV, LL, and %BF), P(max) and its two components (Vopt and Fopt) still increased with age. This indicates that other factors of qualitative nature have to be considered when determining P(max), Vopt, and Fopt.

Influence of two pedalling rate conditions on mechanical output and physiological responses during all-out intermittent exercise

The purpose of this study was to investigate the effect of two cycling velocities on power output and concomitant metabolic and cardiorespiratory responses to repeated all-out exercises. Mean power output (P(m)), total work ( W(tot)), total oxygen consumption (VO(2tot)) and blood lactate accumulation (delta[La](b)) were evaluated in 13 male subjects who performed two series of twelve 5-s bouts of sprint cycling. Recovery periods of 45-s were allowed between trials. One series was executed at optimal velocity (V(opt): velocity for greatest power) and the other one at 50% V(opt) (0.5 V(opt)). Velocities obtained in these conditions were V(opt=)116.6 (4.7) rpm; 0.5V(opt)=60.6 (4.9) rpm. After a phase of adaptation in oxygen uptake in the first part of the series, the data from the 6th to the 12th sprint were as follows: P(m), 924.6 (73.9) versus 689.2 (61.8) W; W(tot), 29.95 (4.14) versus 22.04 (3.17) kJ; VO(2tot), 12.80 (1.36) versus 10.58 (1.37) l; delta[La](b), 2.72 (1.22) versus 0.64 (0.79) mmol x l(-1), respectively (P<0.001). Both W(tot) and VO(2tot) were consistently higher at optimal velocity (+21 and +35.8%, respectively). The present findings demonstrate that during intermittent short-term all-out exercise requiring maximal activation, the energy turnover is not necessarily maximal. It depends on muscle contraction velocity. The increase, lower than expected, in metabolic response from 0.5 V(opt) to V(opt) suggests also that mechanical efficiency is higher at V(opt).

Measurement error in short-term power testing in young people

The aim of this study was to examine the consistency or reproducibility of measuring cycling peak power in children and adults. Twenty-seven pre-pubertal girls and boys and 27 female and male physical education students (age 9.8 +/- 0.5 and 24.4 +/- 4.3 years, respectively; mean +/- s) participated in the study. All participants performed five tests over 15 days and underwent a habituation session before the study. Each test included four sprints against four different braking forces. We found that braking forces of 7.5% of body weight in children and 10% of body weight in adults were too high for most of the participants to elicit maximal cycling power. Unlike the children, the physical education students improved their performance between session 1 and session 2 (1025 +/- 219 vs 1069 +/- 243 W; P < 0.001). Therefore, to obtain reproducible measures of cycling peak power, a habituation session including a complete test protocol (i.e. warm-up plus three sprints) is highly recommended. When the protocol included three sprints in children and at least two sprints in adults, measurement of cycling peak power was found to be highly reliable (test-retest coefficient of variation approximately 3%). Finally, to avoid performance fluctuations, especially over several consecutive evaluations (e.g. longitudinal studies), it is necessary to maintain high motivation in children.

Short-term muscle power during growth and maturation

During growth and maturation, the study of very brief high-intensity exercise has not received the same attention from researchers as, for instance, aerobic function. In anaerobic tasks or sports events such as sprint cycling, jumping or running, the children's performance is distinctly lower than that of adults. This partly reflects children's lesser ability to generate mechanical energy from chemical energy sources during short-term intensive activity. For many years, various attempts have been made to quantify the anaerobic energy yield in maximal-intensity exercise, but many assumptions have had to be made with respect to mechanical efficiency, lactate turnover, dilution space for lactate, and so on. During childhood and adolescence, direct measurements of the rate or capacity of anaerobic pathways for energy turnover presents several ethical and methodological difficulties. Thus, rather than measure energy supply, paediatric exercise scientists have concentrated on measuring short-term muscle power (STMP) by means of standardised tests. Previously, investigators have used various protocols such as short-term cycling power tests, vertical jump tests or running tests. Cycling ergometer tests are the most common. There is, however, no ideal test, and so it is important to acknowledge the limitations of each test. Progress has been made in assessing instantaneous cycling STMP from a single exercise bout. Several investigators have reported STMP increases with age and have suggested that late pubertal period may accentuate anaerobic glycolysis. Mass-related STMP was shown to increase dramatically during childhood and adolescence, whereas the corresponding increase in peak blood lactate was considerably lower. The latter results support the hypothesis that the difference observed between children and adolescents during STMP testing is more related to neuromuscular factors, hormonal factors and improved motor coordination, rather than being an indicator of reduced lactate-producing glycolysis mechanism. Evidence suggesting a causal link between the ability to generate lactate during exercise and sexual maturation is weak. Despite the majority of research being focused on short-term power output, the study of anaerobic function warrants more investigation. Spectacular progress is being made at the moment in the development of molecular biology tools that can be used in, for example, the genetic dissection of human performance phenotypes. Noninvasive power tools like magnetic resonance imaging and magnetic resonance spectroscopy are presently used to determine possible differences in phosphorus compounds between fast and slow fibre types. Undoubtedly these tools will lead to more information in the near future regarding STMP capabilities of the growing child.

Are intensified physical education sessions able to elicit heart rate at a sufficient level to promote aerobic fitness in adolescents?

The purpose of this study was to determine the effects of intensified physical education sessions on adolescents ages 11-16 years. They were divided into two experimental groups--high-intensity running group (HIRG) and high-intensity jumping group (HlJG)--and a control group (C). During the sessions, heart rate (HR) was monitored. There was no significant difference between mean HR for HIRG and HIJG, while the mean HR was significantly lower for C (p < .001). For both HIRG and HIJG, the mean HR was significantly higher for girls than for boys (p < .001). Our results suggested that these intensified physical education lessons require a high percentage of maximal HR in adolescents and can be used to improve aerobic fitness.