Sedentary behaviour and adiposity in elite athletes

Abstract

Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a health risk. Even in athletes an increased adiposity affects health and performance. Sedentary behaviour has been associated with higher levels of adiposity, independent of moderate-to-vigorous physical activity. However, it is unclear whether this independent relationship still exists in highly trained athletes. The aim of this study was to examine the association of sedentary behaviour with body fatness in elite athletes. Cross-sectional data from 82 male athletes (mean age 22 years) were used. Total and regional body composition was measured by dual energy X-ray absorptiometry. Self-reported time spent in sedentary behaviour and weekly training time was assessed in all participants at one time point and multiple regression analyses were used. Sedentary behaviour predicted total fat mass (β = 0.77; 95% CI: 0.36–1.19, P < 0.001) and trunk fat mass (β = 0.25; 95% CI: 0.07–0.43, P = 0.007), independent of age, weekly training time, and residual mass (calculated as weight-dependent variable) but not abdominal fat. Also, no associations of sedentary behaviour with fat-free mass, appendicular lean soft tissue, and body mass index were found. These findings indicate that athletes with higher amounts of sedentary behaviour presented higher levels of total and trunk fatness, regardless of age, weekly training time, and residual mass. Therefore, even high moderate-to-vigorous physical activity levels do not mitigate the associations between sedentary behaviour and body fatness in highly trained athletes.     

Body composition,metabolism, sleep,psychological and eating patterns of overtraining syndrome: Results of the EROS study (EROS-PROFILE)

Overtraining syndrome (OTS) is caused by an imbalance between training, nutrition and resting, and leads to decreased performance and fatigue; however, the precise underlying triggers of OTS remain unclear. This study investigated the body composition, metabolism, eating, sleeping patterns and mood states among participants with OTS. Selected participants were divided into OTS-affected athletes (OTS, n = 14), healthy athletes (ATL, n = 25), and healthy non-physically active controls (NCS, n = 12). Compared to ATL, OTS showed decreased sleep quality (p = 0.004); increased duration of work or study (p < 0.001); decreased libido (p = 0.024); decreased calorie (p < 0.001), carbohydrate (p < 0.001) and protein (p < 0.001) intakes; decreased mood states (p < 0.001); decreased basal metabolic rate (p = 0.013) and fat burning (p < 0.001); increased body fat (p = 0.006); decreased muscle mass (p = 0.008); and decreased hydration (p < 0.001). Levels were similar between OTS and NCS, except for worsened fatigue (p < 0.001) and vigour (p = 0.001) in OTS. Reduced calorie intake, worsened sleep, and increased cognitive activity are likely OTS triggers. OTS appears to induce dehydration, increase body fat, decrease libido, and worsen mood.     

Menstrual cycle alters training strain,monotony, and technical training length in young

The menstrual cycle (MC) phases carry to several psychophysiological alterations; however, no study has investigated the impact of MC phases on training load or technical training. In the present study, we investigated the effect of the follicular phase (FP), ovulatory phase (OP), and luteal phase (LP) on training load and technical training in young athletes. Twelve female athletes performed regular daily training sessions with the rating of perceived exertion (RPE) and duration being registered every session. Training impulse (TRIMP), monotony and strain were calculated. MC symptoms, RPE, and duration were also measured during technical training, which was carried out on a specific day during each phase. The TRIMP was not affected by MC phases during regular training (p > .05), but training monotony and strain were higher in FP compared to OP (p < .05). During the technical training, MC phases did not affect RPE (p > .05), but the session was longer in both FP and LP, compared to OP (p < .05). MC symptoms were exacerbated in FP compared to both OP and LP (p < .05). These findings suggest that MC disorders were elevated during FP, which indicate that monitoring MC phases might provide important feedbacks for programming training and expected results during competitions.     

Aerobic plus resistance training was more effective in improving the visceral adiposity,metabolic profile and inflammatory markers than aerobic training in obese adolescents

Abstract

The purpose of this study was to determine whether aerobic plus resistance training (AT + RT) is more effective than aerobic training (AT) at reducing inflammatory markers and cardiovascular risk in obese adolescents. A total of 139 obese adolescents were enrolled, aged 15–19 years, body mass index (BMI) ≥ 95th percentile and participated in 1 year of interdisciplinary intervention. They were randomised into two groups: AT (n = 55), AT + RT (n = 61). Blood samples were collected to analyse glycaemia, insulin, the lipid profile, leptin and adiponectin concentrations. Insulin resistance was measured by homeostasis model assessment of insulin resistance index (HOMA-IR). The AT + RT group showed better results with regard to decreased body fat mass, low-density lipoprotein concentration (LDL-c) levels, subcutaneous and visceral fat and increased body lean mass. Indeed, a reduction of hyperleptinaemia and an increase in adiponectin concentrations, promoting an improvement in the leptin/adiponectin ratio, was observed. Important clinical parameters were improved in both types of exercise; however, AT + RT was more effective in improving the visceral adiposity, metabolic profile and inflammatory markers than AT alone, suggesting clinical applications for the control of intra-abdominal obesity and cardiovascular risk in the paediatric population.     

Investigating the workload,readiness and physical performance changes during intensified 3-week preparation periods in female national Under18 and Under20 basketball teams

ABSTRACT

This study aimed to investigate between- and within-team changes in workload [PlayerLoad (PL), training impulse (TRIMP) and session rate of perceived exertion training load (sRPE-TL)], readiness [heart rate variability (HRV)], and physical performance [20-m sprint test (including 10-m split time), countermovement jump (CMJ) and yo-yo intermittent recovery test level 1 (YYIR1)] during 3-week intensified preparation periods in female, national Under18 (n = 12, age = 18.0 ± 0.5y, stature = 180.4 ± 7.5 cm, body mass = 72.7 ± 9.3 kg) and Under20 (n = 12, age = 19.6 ± 0.8y, stature = 178.6 ± 6.4 cm, body mass = 68.0 ± 5.9 kg) basketball teams. Under18 team revealed small-to-moderate statistically significantly higher values in workload [PL: p = 0.010; ES = Small; TRIMP: p = 0.004; ES = Moderate; sRPE-TL: p < 0.001; ES = Moderate] and moderately lower readiness values (p = 0.023; ES = Moderate) compared to Under20. Within-team analysis showed no differences in workload in Under20 and statistically significant reduction (p < 0.05) in Week3 (taper period) in Under18. Pre- and post-preparation changes showed Under18 increasing only YYIR1 performance (p < 0.001; ES = Very large). Differently, Under20 statistically improved in 10-m split time (p = 0.003; ES = Moderate), CMJ (p = 0.025; ES = Moderate) and YYIR1 (p < 0.001; ES = Large). A constant adequate workload positively benefits players’ readiness and physical performances during short intensified preparation periods. Conversely, using high workload with periodization strategies encompassing short overload and taper phases induced positive changes on players’ aerobic performance, lower readiness values and no changes in anaerobic performances.     

Autonomic response to a short and long bout of high-intensity functional training

The evaluation of Autonomic Nervous System (ANS) recovery following exercise provides insight into the transient stress placed on the cardiovascular system. High-Intensity Functional Training (HIFT) is a form of intense exercise that is prescribed in various modalities and durations; however, little is known about the influence of HIFT duration on ANS recovery. Ten apparently healthy males (28.1 ± 5.4 yrs) performed two HIFT sessions (<5-minute and 15-minute) in a crossover fashion. ANS activity was measured using plasma Epinephrine (E) and Norepineprine (NE); Heart Rate Variability markers of the log transformed Root Mean Square of Successive Differences (lnRMSSD) and High-Frequency power (lnHF). No trial dependent differences were observed in lnRMSSD (p = 0.822), lnHF (p = 0.886), E (p = 0.078), or NE (p = 0.194). A significant main time effect was observed in both trials with a depression in lnRMSSD and lnHF following the trials (p < 0.05) and recovering by 2-hours post (p = 0.141, p > 0.999) respectively. A trial dependent increase in E and NE occurred immediately post (p < 0.05) and recovered by 1-hour post (p > 0.999, p > 0.999) respectively. The HIFT bouts examined within this study demonstrated similar transient strain of the ANS.     

A comparison of anthropometric and training characteristics of Ironman triathletes and Triple Iron ultra-triathletes

Abstract

We examined differences in anthropometry and training between 64 Triple Iron ultra-triathletes competing over 11.4 km swimming, 540 km cycling, and 126.6 km running, and 71 Ironman triathletes competing over 3.8 km swimming, 180 km cycling, and 42.2 km running. The association of anthropometry and training with race time was investigated using multiple linear regression analysis. The Triple Iron ultra-triathletes were smaller (P < 0.05), had shorter limbs (P < 0.05), a higher body mass index (P < 0.05), and larger limb circumferences (P < 0.01) than the Ironman triathletes. The Triple Iron ultra-triathletes trained for more hours (P < 0.01) and covered more kilometres (P < 0.01), but speed in running during training was slower compared with the Ironman triathletes (P < 0.01). For Triple Iron ultra-triathletes, percent body fat (P = 0.022), training volume per week (P < 0.0001), and weekly kilometres in both cycling (P < 0.0001) and running (P < 0.0001) were related to race time. For Ironman triathletes, percent body fat (P < 0.0001), circumference of upper arm (P = 0.006), and speed in cycling training (P = 0.012) were associated with total race time. We conclude that both Triple Iron ultra-triathletes and Ironman triathletes appeared to profit from low body fat. Triple Iron ultra-triathletes relied more on training volume in cycling and running, whereas speed in cycling training was related to race time in Ironman triathletes.     

Physical profiles of elite,sub-elite,regional and age-group netballers

Physical profile data from elite, sub-elite, regional, under 21s (U21), under 19s (U19) and under 17s (U17) (n = 845) players from a state netball association in Australia were analysed. Within season changes were examined for the elite and sub-elite players. Longitudinal changes were examined for the elite across four consecutive netball seasons.

Elite were significantly older (24.3 ± 3.4years), taller (182.4 ± 7.2cm) and heavier (73.42 ± 6.95kg) than other playing levels (p < 0.001, ES 0.49–3.26) and had higher vertical jump (VJ) data compared to all groups (p < 0.001, ES 0.47–0.93). U17’s were significantly faster than elite, sub-elite and U19 players over 5m (p < 0.05, ES 0.36–0.58) while elite were faster over 20m compared to all groups (p < 0.01, ES 0.45–0.72). Elite achieved a greater distance (1350.8m; p < 0.05, ES 0.32–0.50) in the Yo-YoIRT1 compared to the sub-elite, regional, U19 and U17. VJ height significantly increased from the 2014 (51.6 ± 4.8cm) to the 2017 season (59.6 ± 6.3cm) for the elite players (p < 0.01, ES 1.18). Yo-YoIRT1 test scores increased significantly between the pre-season and in-season phases (p < 0.05, ES 0.17).     

Effects of aerobic training on serum omentin-1 and cardiometabolic risk factors in overweight and obese men

Abstract

Omentin-1 is a newly discovered protein expressed and secreted from visceral adipose tissue that increases insulin sensitivity. We examined the effects of 12 weeks of aerobic training on serum omentin-1 concentrations together with cardiovascular risk factors in overweight and obese men. Eighteen overweight and obese participants (age 43.1 ± 4.7 years, BMI ≥25 kg · m^?2) were assigned to exercise training (n = 9) and control (n = 9) groups. A matched control group of normal weight participants (n = 8; age 42.2 ± 3.8 years, BMI <25 kg · m^?2) were also recruited for baseline comparison. The obese exercise group participated in 12 weeks of progressive aerobic training 5 days a week. Measures of serum omentin-1, insulin resistance, lipid profiles, blood pressure, and body composition were obtained before and after the 12 weeks. At baseline, normal weight participants had significantly higher serum omentin-1 concentrations than overweight and obese participants, and there were inverse correlations between omentin-1 and each of waist circumference, fasting glucose, insulin resistance, total cholesterol, triglyceride, and systolic blood pressure (P < 0.05). After the aerobic training, waist circumference, percent body fat, fasting glucose, insulin resistance, triglyceride, total cholesterol, low-density lipoprotein cholesterol, and systolic blood pressure were all significantly decreased (P < 0.05). In contrast, serum omentin-1 concentration was significantly increased after the aerobic programme (P < 0.05), and correlated with changes in insulin resistance (r = ?0.67, P = 0.04), glucose (r = ?0.65, P = 0.05), waist circumference (r = ?0.70, P = 0.03), and aerobic fitness r = ?0.68, P = 0.04). Aerobic training resulted in an improvement in cardiometabolic risk factors in obese participants, and this improvement was accompanied by increased omentin-1 concentrations.     

Relationships between highly skilled golfers’ clubhead velocity and force producing capabilities during vertical jumps and an isometric mid-thigh pull

Whilst previous research has highlighted significant relationships between golfers’ clubhead velocity (CHV) and their vertical jump height and maximum strength, these field-based protocols were unable to measure the actual vertical ground reaction force (vGRF) variables that may correlate to performance. The aim of this study was to investigate relationships between isometric mid-thigh pull (IMTP), countermovement jump (CMJ), squat jump (SJ) and drop jump (DJ) vGRF variables and CHV in highly skilled golfers. Twenty-seven male category 1 golfers performed IMTP, CMJ, SJ and DJ on a dual force platform. The vertical jumps were used to measure positive impulse during different stretch-shortening cycle velocities, with the IMTP assessing peak force (PF) and rate of force development (RFD). Clubhead velocity was measured using a TrackMan launch monitor at a golf driving range. Pearsons correlation coefficient analyses revealed significant relationships between peak CHV and CMJ positive impulse (r = 0.788, p < 0.001), SJ positive impulse (r = 0.692; p < 0.001), DJ positive impulse (r = 0.561, p < 0.01), PF (r = 0.482, p < 0.01), RFD from 0–150 ms (r = 0.343, p < 0.05) and RFD from 0–200 ms (r = 0.398, p < 0.05). The findings from this investigation indicate strong relationships between vertical ground reaction force variables and clubhead velocity.     

Water-filled training tubes increase core muscle activation and somatosensory control of balance during squat

This study examined trunk muscle activation, balance and proprioception while squatting with a water-filled training tube (WT) and a traditional barbell (BB), with either closed (CE) or open eyes (OE). Eighteen male elite Gaelic footballers performed an isometric squat under the following conditions: BB-OE, BB-CE, WT-OE and WT-CE. The activity of rectus abdominis (RA), external oblique (EO) and multifidus (MF) was measured using electromyography, along with sway of the centre of pressure (CoP) using a force platform. Only the EO and the MF muscles exhibited an increased activity with WT (p < 0.01). In the medio-lateral direction both the velocity and range of the CoP increased significantly with WT (p < 0.01). Interestingly, the range of the CoP for the WT-CE condition was significantly lower than WT-OE (p < 0.05, d = 0.44), whilst the velocity of the CoP was marginally reduced (d = 0.29). WT elicited a greater level core muscle activation and created a greater challenge to postural stability when compared to a BB. It appears that WT does not benefit from vision but emphasises the somatosensory control of balance. The use of WT may be beneficial in those sports requiring development of somatosensory/proprioceptive contribution to balance control.     

高强度间歇训练通过支配内脏脂肪的交感神经活动促进白色脂肪组织棕色化

目的:对比12周高强度间歇训练与中等强度持续训练促进肥胖小鼠内脏与皮下白色脂肪棕色化的效果,分析促进棕色化的交感神经活动及肌肉因子合成与棕色化标志物的相关关系。随后根据相关分析结果,对内脏脂肪交感神经受体进行化学抑制,验证交感神经活动促棕色化的作用。方法:1)效果观察实验,采用雌性C57bl/6小鼠经高糖高脂膳食诱导建立肥胖动物模型后,随机分为肥胖对照组(HFD)、中等强度持续运动组(MICT)和高强度间歇训练组(HIIT),HFD组不运动,MICT组进行中等强度跑台训练,HIIT组进行高强度间歇跑台训练。训练周期12周,期间3组均继续进行高糖高脂饲养。训练结束后测量子宫周围内脏脂肪与腹股沟皮下脂肪重量,H.E.染色观察脂肪细胞形态,蛋白免疫印迹观察骨骼肌过氧化物酶体增殖物激活受体γ辅激活因子1α(peroxisome proliferator-activated receptor gamma coactivator 1-alpha,PGC-1α)、纤维连接蛋白Ⅲ型结构域蛋白5(fibronectin typeⅢdomain-containing protein 5,FNDC5)、脂肪酪氨酸羟化酶(tyrosine hydroxylase,TH)及解偶联蛋白1(uncoupling protein-1,UCP-1)表达;2)机制验证实验,12只小鼠随机分为安慰剂组(Saline)与拮抗剂组(SR),两组均进行10天HIIT训练,SR组每次训练前2 h腹腔注射脂肪交感神经受体拮抗剂SR59230a,Saline组注射生理盐水,训练结束后蛋白免疫印迹观察内脏与皮下脂肪UCP-1表达。结果:1)HIIT组与MICT组体重均非常显著低于HFD组(P<0.01),HIIT组子宫周围内脏脂肪重量显著低于HFD组与MICT组(P<0.05),同时,内脏脂肪细胞体积HIIT组0.05),内脏与皮下脂肪FNDC5与UCP-1均无显著相关性;2)SR组内脏脂肪UCP-1表达显著低于Saline组(P<0.05)。结论:HIIT相比MICT可更显著的促进内脏白色脂肪组织棕色化,且此过程与脂肪交感神经调控密切相关。     

Effects of a feint on reactive agility performance

Abstract

This study compared reactive agility between higher-standard (n = 14) and lower-standard (n = 14) Australian footballers using a reactive agility test incorporating a life-size video image of another player changing direction, including and excluding a feint. Mean agility time in the feint trials was 34% (509 ± 243 ms; p < 0.001; effect size 3.06) longer than non-feint trials. In higher-standard players, agility time was shorter than for lower-standard players in both feint (114 ± 140 ms; p = 0.18; effect size 0.52; likely beneficial) and non-feint (32 ± 44 ms; p = 0.22; effect size 0.47; possibly beneficial) trials. Additionally, the inclusion of a feint resulted in movement time increasing over three times more in the lower-standard group (197 ± 91 ms; p = 0.001; effect size 1.07; almost certainly detrimental) than the higher-standard group (62 ± 86 ms; p = 0.23; effect size 0.66; likely detrimental). There were weak correlations between the feint and non-feint trials (r = ?0.13–0.14; p > 0.05), suggesting that reactive agility involving a feint is a unique skill. Also, higher-standard players are more agile than their lower-standard peers, whose movement speed deteriorates more as task complexity increases with the inclusion of a feint. These results support the need for specific training in multi-turn reactive agility tasks.     

Angle-specific knee muscle torques of ACL-reconstructed subjects and determinants of functional tests after reconstruction

The purposes of this study were to analyse (a) if “angle-specific” (AS) flexor and extensor torques were different between ACL-reconstructed and uninvolved limbs, (b) the difference in peak torque occurrence angles for concentric and eccentric knee flexor and extensor torques between involved and uninvolved limbs and (c) if AS concentric and eccentric knee flexor and extensor torques are determinants of performance in the “single-leg hop test” (SLHT) and “vertical jump and reach test” (VJRT) in ACL-reconstructed legs. Twenty-seven male ACL-reconstructed volunteers were included in the study. Isokinetic knee muscle strength, SLHT and VJRT were performed 6 months after ACL reconstruction. No difference was found in extremity and knee joint angle interaction for concentric and eccentric flexor and extensor torques (p > 0.05). Peak torque occurrence angles were not different between involved and uninvolved limbs (p > 0.05). In involved extremities, concentric knee extensor strength at 90° was a determinant of SLHT performance (R² = 0.403, p < 0.05), and concentric knee extensor strength at 60° was a determinant of VJRT (R² = 0.224, p < 0.05). Assessment of AS concentric knee extensor strength at 60° and 90° might be important, because these were determinants of functional test performance.     

Does ball carrier technique influence tackler head injury assessment risk in elite rugby union?

The aim of this study was to use video evidence of tackles in elite level rugby union to identify ball carrier proficiency characteristics, for both lower and upper body tackles, that have a higher propensity to result in Head Injury Assessments(HIA) for the tackler. HIA (n = 74) and non-HIA tackles (n = 233) were categorised as either front-on or side-on upper or lower body tackles and scored for ball carrying proficiency characteristics. Side-on tackles included tackles from behind. A Chi-Square test (p < 0.05) and Cramer’s V were calculated to compare proficiency characteristics in HIA and non-HIA cases. For front-on upper body tackles, the ball carrier “fending into contact” (p < 0.01;ES = Moderate) and “explosiveness on contact” (p = 0.04;ES = Moderate) had a higher propensity to result in a HIA for the tackler. Fending into contact was exhibited in 47% of all upper body Tackle front-on HIA cases. The fending arm contacted the tackler’s head in 67% of these cases. Fending into contact can potentially be dangerous and therefore emphasis should be placed on safe fending during tackle-based training drills. Referees should also be alert to arm-to-head contact during the fend. Given the low number of ball carrier characteristics identified, focus should be placed on tackler characteristics for HIA prevention strategies.     

Relationship between weight status and cognition in children: A mediation analysis of physical fitness components

ABSTRACT

Cross-sectional study aimed to analyse differences in cognitive performance across fitness components categories (cardiorespiratory fitness [CRF], speed-agility and muscular fitness [MF]) and weight status in children, and to determine whether physical fitness mediates the association between body mass index (BMI) and cognitive performance. Fitness components and BMI were measured using standard procedures in 630 children aged 5-to-7 years from the provinces of Cuenca and Ciudad Real, Spain. BADyG was used to assess cognitive performance. We used ANCOVA models to test mean differences in cognition scores by BMI and fitness categories. Hayes’s PROCESS macro was used for mediation analyses. Children with normal weight scored better in spatial factor and general intelligence than their overweight/obese peers (p < 0.05), but differences were attenuated when controlling for CRF (p > 0.05). Children with better results in CRF and speed-agility scored better in all cognitive dimensions even after controlling for BMI (p < 0.05). Similarly, children with high MF obtained better scores in verbal factor (p < 0.05). All fitness components acted as mediators of the relationship between BMI and general intelligence (p < 0.05). These findings highlight the crucial role of fitness in minimising the negative effect of excess weight on children’s cognition.

Abbreviations: BMI: Body mass index; CRF: Cardiorespiratory fitness; MF: Muscular fitness; BADyG E1: Battery of general and differential aptitudes; SES: Socioeconomic status; SD: Standard deviation; IE: Indirect effect     

Evaluierung von unterschiedlichen Trainingsmodellen bei berufstätigen Freizeitläufern

The aim of the study was to examine the effects of three different training models on aerobic power and body composition in recreationally active runners. According to their preferences 54 subjects (female=?27, male?=?27) were assigned to the following groups: (a) weekend group (WE), who performed two sessions of continuous endurance training weekly, (b) after-work group (FE) who carried out four sessions of high intensity training as well as an additional endurance run and (c) STAR group (STAR), who took part in a training with exercise telemetry monitors based on the heart rate variability. Over the 12-week study period the mean training volume was approximately 2 h 15 min per week. Of the participants 47 successfully completed the training study and all 3 groups showed significantly improved aerobic power (p?<0.001); however, the FE group (d?=?1.15) showed increased VO_2max superior to WE (d?=?0.48) and STAR (d?=?0.66) groups. Significant improvements in body mass (p?<?0.001), body fat (p?<?0.001) and visceral fat (p?<?0.001) were found in the WE, FE and STAR group. All groups completed the half marathon with no significant differences in performance. Based on a similar training volume, short, intensive endurance training sessions of about 30 min were found to elicit the greatest improvements of VO2max in recreationally active runners.     

Effects of a power-focussed resistance training intervention on backward grinding performance in America's Cup sailing

This study determined whether backward grinding performance in America's Cup sailing could be improved using a training intervention to increase power capability in the upper-body pull movement. Fourteen elite male sailors (34.9 ± 5.9 years; 98.1 ± 14.4 kg; 186.6 ± 7.7 cm) were allocated into experimental (speed-focussed) and control groups. Grinding performance was assessed using a grinding ergometer and an instrumented Smith machine measured force, velocity and power during the bench pull exercise. Conventional training produced significant improvements in bench pull 1 RM (5.2 ± 4.0%; p = 0.016) and maximum force production (5.4 ± 4.0%; p = 0.014). Speed-focussed training improved maximum power (7.8 ± 4.9%; p = 0.009), power at 1RM (10.3 ± 8.9%; p = 0.019) and maximum velocity (8.4 ± 2.6%; p = 0.0002). Backward grinding performance showed greater improvements in the experimental group than the control group for moderate (+1.8%) and heavy load (+6.0%) grinding. Changes in maximum power output and power at 1 RM had large correlations (r = 0.56–0.61) with changes in both moderate and heavy load grinding performance. Time to peak force had the strongest relationship, explaining 70% of the change in heavy load grinding performance. Although the performance benefit was not entirely clear the likelihood of a detrimental effect was low ( < 5%) and therefore implementation could be recommended.     

A cross-sectional and prospective analyse of reallocating sedentary time to physical activity on children’s cardiorespiratory fitness

Cardiorespiratory fitness (CRF) is associated with health benefits in children, improving cardiac morphology, cardiovascular disease risk factors, and biological outcomes. This study aimed to examine the substitution effects of displaying a fixed duration of sedentary time with a fixed duration of physical activity (PA) at different intensities on children’s CRF. A total of 315 children (136 boys) were assessed (age: 10.6 ± 0.6 years old). Outcomes at baseline and follow-up (16-months) were CRF determined using a maximal cycle test and sedentary time and PA measured with accelerometers. Data were analysed by isotemporal substitution analyses estimating the effect of reallocating 30 min/day of sedentary time by light (LPA), moderate (MPA) and vigorous physical activity (VPA) on CRF. VPA was positively and significantly associated with CRF cross-sectional (β = 0.026, p < 0.001) and prospectively (β = 0.010, p < 0.001). Reallocating 30 min/day of sedentary time into VPA was positively cross-sectionally (β = 0.780, p < 0.001) and prospectively (β = 0.303, p < 0.05) associated with CRF. Conversely, relocating 30-minutes of sedentary time into 30 minutes of LPA and MPA was not associated with CRF. These results suggest that reallocating an equal amount of time from sedentary into VPA is cross-sectional and prospectively associated with a favourable CRF.