The association of range of motion, lower limb strength, and load during jump landings in professional ballet dancers

This study aimed to investigate the associations between peak plantarflexion ankle joint moments and vertical ground reaction forces (vGRF) during jump landings, and static ankle dorsiflexion range of motion (ROM), three-dimensional ankle excursions, and lower extremity strength in professional ballet dancers. Twenty-seven professional ballet dancers volunteered to participate (men = 14, women = 13). Participants attended one data collection session to measure dorsiflexion ROM and isometric lower extremity strength. Two further sessions were used to establish ankle mechanics and vGRFs during countermovement jump landings in seven foot positions, via a seven-camera motion capture system and piezoelectric force platform. Two linear mixed-effects models were used to investigate associations between the target variables and strength, dorsiflexion ROM, and ankle excursions. Dancer identification, sex, and foot position were entered as random effects. Model fit, when considered independent of random effects, was generally poor with the predictor variables explaining little of the variance of peak plantarflexion ankle joint moments (R2 = 0.02) or vGRF (R2 = 0.01). Model fit improved when random effects were considered (R2 = 0.65 & 0.34). Frontal plane ankle excursion was the only predictor variable with a significant negative association with peak plantarflexion ankle joint moments (p = .016), although coefficient estimates were small. Strength, static ankle dorsiflexion ROM, and three-dimensional ankle excursions are poor predictors of load experienced at a joint and system level in professional ballet dancers. Differences between individuals, sex, and foot position may be better indicators of the load experienced during jump landings.

Jumping Asymmetries and Risk of Injuries in Preprofessional Ballet

BACKGROUND

Preprofessional ballet dancers are exposed to the risk of injuries, primarily in the lower extremities, with most injuries occurring during jumping and landing activities. Interlimb asymmetry during jumping and landing activities has been associated with the injury risk in adolescent athletes, but this has not been examined in dancers.

PURPOSE

To investigate associations between interlimb asymmetry during a double-leg countermovement jump (DL-CMJ) and single-leg jump (SLJ) and the injury risk in adolescent preprofessional ballet dancers.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Adolescent preprofessional ballet dancers (N = 255) performed 3 DL-CMJs and 3 SLJs on force plates during annual screening. Absolute and directional (separate values for left and right limb dominance) asymmetries in a set of kinetic variables during a DL-CMJ and in jump height during an SLJ were calculated. Each variable was characterized as having "high" or "normal" asymmetry according to the percentage of asymmetry (greater than or less than or equal to, respectively, the mean ± 0.5 SD) based on the present sample. Risk ratios (RRs) and 95% CIs were calculated based on the injury incidence in the subsequent academic year.

RESULTS

Of the 242 dancers that satisfied the inclusion criteria, 128 injuries were observed in the subsequent academic year. In the whole sample, 3 absolute, 7 left limb-dominant, and 1 right limb-dominant kinetic asymmetry in the eccentric, concentric, and landing phases of the DL-CMJ as well as left limb-dominant jump height asymmetry in the SLJ were associated with a significant (P < .001) increase in the injury risk (RR, 1.28-1.69 [95% CI, 1.02-2.37]). Separating by sex, asymmetries in the eccentric and landing phase of the DL-CMJ were not significant in boys, while in girls, RRs for asymmetries in the eccentric and landing phase of the DL-CMJ increased, and SLJ jump height asymmetry was not significant.

CONCLUSION

Higher asymmetries in certain kinetic variables during the DL-CMJ and in jump height during the SLJ were associated with an elevated risk of injuries in elite preprofessional ballet dancers with some sex-specific differences. Associations were mainly identified for high left limb-dominant asymmetry in the takeoff phase, suggesting that the injury risk may be specific to a relative right limb deficit.

Waist circumference cut-off points to identify major cardiovascular events and incident diabetes in Latin America: findings from the prospective Urban rural epidemiology study Colombia

Background

Abdominal obesity (AO) indirectly represents visceral adiposity and can be assessed by waist circumference (WC) measurement. In Latin America, cut-off points for the diagnosis of AO are based on Asian population data. We aim to establish the WC cut-off points to predict major cardiovascular events (MACE) and incident diabetes.

Methods

We analyzed data from the cohort PURE study in Colombia. WC cut-off points were defined according to the maximum Youden index. Multivariate logistic regression was used to obtain associations between WC and MACE, diabetes, and cumulative incidence of outcomes visualized using Kaplan-Meier curves.

Results

After a mean follow-up of 12 years, 6,580 individuals with a mean age of 50.7 ± 9.7 years were included; 64.2% were women, and 53.5% were from rural areas. The mean WC was 85.2 ± 11.6 cm and 88.3 ± 11.1 cm in women and men, respectively. There were 635 cases of the MACE composite plus incident diabetes (5.25 events per 1,000 person-years). Using a cut-off value of 88.85 cm in men (sensitivity = 0.565) and 85.65 cm in women (sensitivity = 0.558) resulted in the highest value for the prediction of the main outcome. These values were associated with a 1.76 and 1.41-fold increased risk of presenting the composite outcome in men and women, respectively.

Conclusions

We defined WC cut-off points of 89 cm in men and 86 cm in women to identify the elevated risk of MACE and incident diabetes. Therefore, we suggest using these values in cardiovascular risk assessment in Latin America.

Handgrip Strength Is Associated with Specific Aspects of Vascular Function in Individuals with Metabolic Syndrome

BACKGROUND

Metabolic syndrome (MetS) is a disorder associated with an increased risk for the development of diabetes mellitus and its complications. Lower isometric handgrip strength (HGS) is associated with an increased risk of cardiometabolic diseases. However, the association between HGS and arterial stiffness parameters, which are considered the predictors of morbidity and mortality in individuals with MetS, is not well defined.

OBJECTIVE

To determine the association between HGS and HGS asymmetry on components of vascular function in adults with MetS.

METHODS

We measured handgrip strength normalized to bodyweight (HGS/kg), HGS asymmetry, body composition, blood glucose, lipid profile, blood pressure, pulse wave velocity (PWV), reflection coefficient (RC), augmentation index @75 bpm (AIx@75) and peripheral vascular resistance (PVR) in 55 adults with a diagnosis of MetS between 25 and 54 years old.

RESULTS

Mean age was 43.1 ± 7.0 years, 56.3% were females. HGS/kg was negatively correlated with AIx@75 (r = -0.440), p < 0.05, but these associations were not significant after adjusting for age and sex. However, when interaction effects between sex, HGS/kg and age were examined, we observed an inverse relationship between HGS/kg and AIx@75 in the older adults in the sample, whereas in the younger adults, a weak direct association was found. We also found a significant association between HGS asymmetry and PVR (beta = 30, 95% CI = 7.02; 54.2; p <0.012).

CONCLUSIONS

Our findings suggest that in people with MetS, maintaining muscle strength may have an increasingly important role in older age in the attenuation of age-related increases in AIx@75-a marker of vascular stiffness-and that a higher HGS asymmetry could be associated with a greater vascular resistance.

Sensitivity of Countermovement Jump Variables in Professional Rugby Union Players Within a Playing Season

ABSTRACT

Howarth, DJ, McLean, BD, Cohen, DD, and Coutts, AJ. Sensitivity of countermovement jump variables in professional rugby union players within a playing season. J Strength Cond Res 37(7): 1463-1469, 2023-The aim of this study was to explore the measurement sensitivity of a wide range of countermovement jump (CMJ) variables to a full European professional rugby union season. A secondary purpose was to compare 3 different data treatment methods for the calculation of CMJ variables. Twenty-nine professional rugby union players (mean ± SD; age 24 ± 4 years, height 183.7 ± 8.0 cm, body mass 101.6 ± 10.7 kg) completed a minimum of 12 CMJ testing sessions on Thursdays-a day preceded by a rest day and a minimum of 96 hours after a match-throughout a season. Measurement sensitivity, quantified by signal-to-noise ratio (SNR), was determined for 74 CMJ variables and was calculated by dividing the signal, (week-to-week variation expressed as a coefficient of variation [CV%]) by the noise (interday test/retest reliability expressed as CV%). We also identified variables which had no overlap between the 95% confidence intervals (CIs) for the signal and the noise. The 3 data treatment methods for comparison were (a) mean output across 3 jump trials (Mean3), (b) single output from the trial with the highest jump (BestJH), and (c) the trial with the highest flight time to contraction time ratio (BestFTCT). Most variables had an SNR >1.0 (Mean3 = 60/74; BestFTCT = 59/74; BestJH = 48/74). Fewer variables displayed a nonoverlap of 95% CIs (Mean3 = 23/60; BestFTCT = 22/59; BestJH = 16/48). Most CMJ variables during a professional rugby season demonstrated a signal that exceeded measured noise (SNR > 1.0) and that using the Mean3 or BestFTCT data treatment methods yields a greater number of variables considered sensitive within a season (i.e., SNR > 1.0) than when using BestJH. We also recommend the calculation of the 95% CIs for both signal and noise, with nonoverlap indicative of a greater probability that the responsiveness of the variable at team level (i.e., SNR) also applies at the individual level. As sensitivity analysis is cohort and environment specific, practitioners should conduct a sensitivity analysis using internal signal and noise data to inform their own monitoring protocols.

Reliability of ankle mechanics during jump landings in turned-out and parallel foot positions in professional ballet dancers

This study aimed to determine the within- and between-session reliability of ankle mechanics and vertical ground reaction forces (vGRF) during jump landings in turned-out and parallel foot positions in professional ballet dancers. Twenty-four professional ballet dancers (men = 13, women = 11) attended two data collection sessions where they completed five maximal countermovement jumps in each foot position. The ankle joint mechanics and vGRF of the right limb were recorded via a seven-camera motion capture system and one force platform. Within- and between-session intraclass correlation coefficients (ICC), coefficients of variation (CV), standard error of measurement, and minimal detectable change were calculated for three-dimensional ankle excursion, peak ankle angle, ankle joint velocity, moment, and power, as well as peak landing vGRF, time to peak landing vGRF, loading rate, and jump height. Across both foot positions, within- (ICC: 0.17-0.96; CV: 1.4-82.3%) and between-session (ICC: 0.02-0.98; CV:1.3-57.1%) reliability ranged from poor to excellent, with ankle excursion, peak ankle angle, and jump height demonstrating the greatest ICC values (ICC: 0.65-0.96; CV: 1.4-57%). Jump landings in a turned-out foot position demonstrated better within-session reliability compared to a parallel position, however, no difference in between-session reliability across the foot positions was observed. Most ankle mechanics provide adequate between-session, but not within-session, reliability during jump landings in professional ballet dancers.

Reductions in systolic blood pressure achieved by hypertensives with three isometric training sessions per week are maintained with a single session per week

Isometric handgrip or (wall) squat exercise performed three times per week produces reductions in systolic blood pressure (SBP) in adults with hypertension. We aimed to compare these interventions and the potential to retain benefits with one exercise session per week. We compared blood pressure changes following handgrip and squat isometric training interventions with controls in a randomized controlled multicentre trial in 77 unmedicated hypertensive (SBP ≥ 130 mmHg) adults. Exercise sessions were performed in the workplace and consisted of four repetitions-three sessions per week for the first 12 weeks (phase 1), and one session per week for the subsequent 12 weeks (phase 2). Office blood pressure (BP) was measured at baseline, post-phase 1 and post-phase 2. Post-phase 1, mean reductions in SBP were significantly greater in handgrip (-11.2 mmHg, n = 28) and squat (-12.9 mmHg, n = 27) groups than in controls (-.4 mmHg; n = 22) but changes in DBP were not. There were no significant within-group changes during phase 2 but SBP was 3.8 mmHg lower in the wall squat than the handgrip group-a small magnitude but clinically important difference. While both interventions produced significant SBP reductions, the wall squat appears to be more effective in maintaining benefits with a minimal training dose. The low time investment to achieve and retain clinically significant SBP reductions-42 and 12 min, respectively-and minimal cost, particularly of the wall squat, make it a promising intervention for delivery in public health settings.

Neuromuscular Performance Changes in Elite Futsal Players Over a Competitive Season

ABSTRACT

Spyrou, K, Alcaraz, PE, Marín-Cascales, E, Herrero-Carrasco, R, Cohen, DD, and Freitas, TT. Neuromuscular performance changes in elite futsal players over a competitive season. J Strength Cond Res XX(X): 000-000, 2022-A professional futsal season imposes a great amount of physiological and mechanical stress on players. The main aim of this study was to examine the changes in neuromuscular performance qualities across the season. Ten professional male players performed a 10-m sprint, standing long jumps (SLJs), and countermovement jumps (CMJs) during the competitive season (i.e., every ∼5 weeks from September to January). A one-way repeated measures ANOVA with post hoc pairwise comparisons and effect sizes (ESs) were used to analyze potential differences among these assessments. A significant and large decline was found in concentric peak power (p = 0.040; ES = 1.24). A nonsignificant and moderate decrease was observed in sprint ability (p = 0.155; ES = 1.03), CMJ height (p = 0.175; ES = 1.00), and SLJ distance (p = 0.164; ES = 1.03). Regarding other CMJ kinetic variables, nonsignificant and moderate changes were found. In summary, considering the neuromuscular performance tests and variables assessed, only concentric peak power in CMJ decreased significantly across the season; however, nonsignificant decrements were observed in sprinting time, SLJ, CMJ height, and other kinetic metrics. CMJ variables during the jump-land cycle should be incorporated alongside more traditional measures (e.g., jump height) to monitor performance during the season.

Muscular Strength in Risk Factors for Cardiovascular Disease and Mortality: A Narrative Review

Cardiovascular disease is the leading cause of death globally, accounting for approximately 32% of all deaths in 2019. There has been increasing interest in understanding the role of low muscular strength as a risk factor for cardiovascular disease, given its association with other cardiovascular risk factors such as hypertension, diabetes mellitus, and metabolic syndrome. An inverse association between muscle strength, chronic disease, all-cause mortality, and cardiovascular-related death has been reported. Recent clinical trials have consistently shown that resistance exercise, which increases strength, and potentially muscle mass, significantly improves the control of known cardiovascular disease risk factors and reduces the risk of all-cause death and cardiovascular mortality. In the present article, we review the growing body of evidence that supports the need for future research to evaluate the potential of handgrip strength as a screening tool for cardiovascular disease and its risk factors in the clinical medical setting, as part of routine care using an affordable handgrip strength device. Moreover, it is crucial to devise large-scale interventions driven by governmental health policies to educate the general population and healthcare professionals about the importance of muscular strengthening activities and to promote access to these activities to improve cardiometabolic health and reduce incidence of cardiovascular disease and mortality.

Biomechanical and Neuromuscular Performance Requirements of Horizontal Deceleration: A Review with Implications for Random Intermittent Multi-Directional Sports

Rapid horizontal accelerations and decelerations are crucial events enabling the changes of velocity and direction integral to sports involving random intermittent multi-directional movements. However, relative to horizontal acceleration, there have been considerably fewer scientific investigations into the biomechanical and neuromuscular demands of horizontal deceleration and the qualities underpinning horizontal deceleration performance. Accordingly, the aims of this review article are to: (1) conduct an evidence-based review of the biomechanical demands of horizontal deceleration and (2) identify biomechanical and neuromuscular performance determinants of horizontal deceleration, with the aim of outlining relevant performance implications for random intermittent multi-directional sports. We highlight that horizontal decelerations have a unique ground reaction force profile, characterised by high-impact peak forces and loading rates. The highest magnitude of these forces occurs during the early stance phase (< 50 ms) and is shown to be up to 2.7 times greater than those seen during the first steps of a maximal horizontal acceleration. As such, inability for either limb to tolerate these forces may result in a diminished ability to brake, subsequently reducing deceleration capacity, and increasing vulnerability to excessive forces that could heighten injury risk and severity of muscle damage. Two factors are highlighted as especially important for enhancing horizontal deceleration ability: (1) braking force control and (2) braking force attenuation. Whilst various eccentric strength qualities have been reported to be important for achieving these purposes, the potential importance of concentric, isometric and reactive strength, in addition to an enhanced technical ability to apply braking force is also highlighted. Last, the review provides recommended research directions to enhance future understanding of horizontal deceleration ability.

Who is meeting the strengthening physical activity guidelines by definition: A cross-sectional study of 253 423 English adults?

The current UK physical activity guidelines recommend that adults aged 19 to 65 years perform activity to strengthen muscle and bone a minimum of twice weekly. The number of adults meeting strengthening activity guidelines is lower than for aerobic activity, but estimates vary between studies partly due to differences in how muscle-strengthening activity is defined. We aimed to provide estimates for strengthening activity prevalence in English adults based on a nationally representative sample of n = 253,423 18-65-year-olds. We attempted to quantify the variation in estimates attributable to differences in the way strengthening activity is defined. Finally, we aim to provide a brief descriptive epidemiology of the factors associated with strengthening activity. Adults met guidelines for aerobic activity if they reported the activity equivalent to >150 min/week moderate-intensity exercise. Respondents met strengthening guidelines if they reported at least two bouts per week of strengthening activity. We defined strengthening activity, first, according to criteria used in the Health Survey for England (HSE). Second, we counted bouts of strengthening activities for which we could find evidence of health-related benefits (Evidence). Third, we included bouts of strengthening activity as defined in current UK physical activity guidelines (Guideline). Two-thirds (67%) of adults met guidelines for aerobic activity (69% of men, 65% of women). Less than one-third (29% of men and 24% of women) met guidelines for the HSE definition of strengthening activity. Under the Evidence definition, 16% of men and 9% of women met strengthening guidelines. Using the most-stringent definition (Guideline) just 7.3% of men and 4.1% of women achieved the recommendations for strengthening activity. We found females and older adults (50–65 years) were less likely to meet guidelines for aerobic, strengthening, and combined aerobic plus strengthening activity. The prevalence of meeting activity guidelines was lower in adults from more deprived areas (compared with the least deprived); Adults with lower academic qualifications (Level 1) were less likely to meet activity guidelines than those educated to Level 4 (Degree Level) or higher. Having a limiting disability was associated with a lower prevalence of meeting activity guidelines. Associations between socio-demographic measures and the prevalence of adults meeting activity guidelines were stronger for strengthening activity than for aerobic 51(or combined aerobic plus strengthening) activity Compared with aerobic activity, fewer adults engage in strengthening activity regardless of how it is defined. The range in estimates for how many adults meet strengthening activity guidelines can be explained by variations in the definition of ‘strengthening’ that are used and the specific sports or activities identified as strengthening exercise. When strengthening activity is included, the proportion of English adults meeting current physical activity guidelines could be as high as 1 in 3 but possibly as low as just 1 in 20. A harmonized definition of strengthening activity, that is aligned with physical activity guidelines, is required to provide realistic and comparable prevalence estimates.

Ethnic Differences in the Prevalence of Hypertension in Colombia: Association With Education Level

BACKGROUND

A higher prevalence of hypertension is reported among Afro-descendants compared with other ethnic groups in high-income countries; however, there is a paucity of information in low- and medium-income countries.

METHODS

We evaluated 3,745 adults from 3 ethnic groups (552 White, 2,746 Mestizos, 447 Afro-descendants) enrolled in the prospective population-based cohort study (PURE)-Colombia. We assessed associations between anthropometric, socioeconomic, behavioral factors, and hypertension.

RESULTS

The overall prevalence of hypertension was 39.2% and was higher in Afro-descendants (46.3%) than in Mestizos (37.6%) and Whites (41.5%), differences that were due to the higher prevalence in Afro-descendant women. Hypertension was associated with older age, increased body mass index, waist circumference and waist-to-hip ratio, independent of ethnicity. Low education was associated with hypertension in all ethnic groups, and particularly in Afro-descendants, for whom it was the factor with the strongest association with prevalence. Notably, 70% of Afro-descendants had a low level of education, compared with 52% of Whites-26% of Whites were university graduates while only 7% of Afro-descendants were. We did not find that education level alone had a mediator effect, suggesting that it is not a causal risk factor for hypertension but is an indicator of socioeconomic status, itself an important determinant of hypertension prevalence.

CONCLUSIONS

We found that a higher prevalence of hypertension in Colombian Afro-descendants than other ethnic groups. This was principally associated with their lower mean educational level, an indicator of lower socioeconomic status.

Contextual considerations using the 'control-chaos continuum' for return to sport in elite football - Part 1: Load planning

The 'control-chaos continnum' is an adaptable framework developed to guide the on-pitch rehabilitation process in elite football. One of the key objectives of the continuum is to progressively return players to their preinjury chronic running load, while incorporating the qualitative aspects of movement and cognitive stresses integral to competitive match-play. Whilst injury and player-specific considerations are key to an individualised rehabilitation approach, a host of contextual factors also play an important role in return to sport (RTS) planning. In this article, we highlight some key intrinsic and extrinsic contextual factors for the practitioner to consider in the RTS planning process to help mitigate reinjury risk upon a return to team training. While a return to chronic running load is generally a critical component of the framework, we highlight circumstances in elite football where it is a less relevant factor in RTS decision-making.

Effects of the COVID-19 Lockdown on Neuromuscular Performance and Body Composition in Elite Futsal Players

ABSTRACT

Spyrou, K, Alcaraz, PE, Marín-Cascales, E, Herrero-Carrasco, R, Cohen, DD, Calleja-Gonzalez, J, Pereira, LA, Loturco, I, and Freitas, TT. Effects of the COVID-19 lockdown on neuromuscular performance and body composition in elite futsal players. J Strength Cond Res 35(8): 2309-2315, 2021-Recent world events (i.e., COVID-19 pandemic) led to an unparalleled situation in sports. Players were forced to stay at home for a prolonged period and not allowed to use their team's training facilities or even exercise outdoors. The main aim of this study was to examine the effects of the COVID-19 lockdown on neuromuscular performance and body composition in futsal players. Ten elite male players performed a 10-m sprint, horizontal and vertical jump, and body composition measurements before and after the quarantine (i.e., 70 days). Pre-post confinement differences in horizontal jump distance, countermovement jump variables, sprinting time, and body composition were analyzed by a paired sample t-test and effect sizes (ESs). A large and significant decline was observed in sprint ability (p = 0.004; ES = 1.31). Small and nonsignificant differences were found in horizontal jump performance (p = 0.243; ES = -0.39). Nonsignificant differences were observed in countermovement jump (CMJ) height (p = 0.076; ES = -0.63) but moderate-to-large significant declines were found in CMJ eccentric deceleration impulse, rate of force development, peak power, velocity, and landing peak force (p ≤ 0.05; ES = -0.52 - 1.23). Finally, trivial and nonsignificant differences were obtained on body composition parameters. In summary, sprint performance and specific CMJ kinetic variables were significantly affected by long-term reduced training, whereas vertical jump height and horizontal jump distance and body composition were not. Practitioners are advised to implement efficient sprint-oriented and eccentric-oriented training strategies to optimize return to competition after prolonged detraining periods.

Evaluation of cardiometabolic profile in Health Professionals of Latin America

OBJECTIVE

To evaluate presence of risk factors for cardiovascular diseases (CVD) and type 2 diabetes mellitus (DM2) in a group of health care workers.

METHODS

During the X Latin American Congress of Internal Medicine held in August 2017, in Cartagena, Colombia, attendees were invited to participate in the study that included a survey on medical, pharmacological and family history, lifestyle habits, blood pressure measurement, anthropometry, muscle strength and laboratory studies. The INTERHEART and FINDRISC scales were used to calculate the risk of CVD and diabetes, respectively.

RESULTS

Among 186 participants with an average age of 37.9 years, 94% physicians (52.7% specialists), the prevalence of hypertension was 20.4%, overweight 40.3%, obesity 19.9%, and dyslipidemia 67.3%. 20.9% were current smokers or had smoked, and 60.8% were sedentary. Hypertensive patients were found to be older, had higher Body Mass Index (BMI), higher waist circumference, higher waist-to-hip ratio, higher of body fat and visceral fat, smoked more and had lower muscle strength (high jump: 0.38 vs. 0.42̊cm; p̊=̊0.01). In 44.3% of participants was observed a high-risk score for CVD. The prevalence of diabetes was 6.59% and 27.7% were at risk.

CONCLUSION

The prevalence of risk factors for CVD among the Latin American physicians studied was similar to that reported in the general population. The prevalence of high-risk scores for CVD and DM2 was high and healthy lifestyle habits were low. It is necessary to improve adherence to healthy lifestyles among these physicians in charge of controlling these factors in the general population.

Drop jump neuromuscular performance qualities associated with maximal horizontal deceleration ability in team sport athletes

The purpose of this study was to investigate associations between, and within, drop jump (DJ) neuromuscular performance (NMP) qualities and maximal horizontal deceleration ability. We also compared DJ NMP qualities in "high" versus "low" horizontal deceleration ability athletes. Twenty-nine university athletes performed: (1) DJs on force plates from 20 (DJ20) and 40 cm (DJ40) heights and (2) maximal horizontal deceleration, measured using radar, following a 20 m acceleration. Maximal horizontal deceleration was evaluated using deceleration (HDEC; m·s^-2), across the entire deceleration phase and during early and late deceleration sub-phases. Of the DJ variables assessed, DJ20 and DJ40 reactive strength index (RSI) and concentric mean force had the largest correlations with HDEC (r = -0.54 to -0.61) and the largest differences between high and low HDEC groups (d = 1.20 to 1.40). These correlations were stronger with the early than late HDEC sub-phase (r = -0.54 to -0.66 vs. r = -0.24 to -0.40). Notably, eccentric mean force in DJ40 had large correlations with both DJ20 and DJ40 concentric mean force (r = 0.67 to 0.77), whereas at DJ20 these correlations were small (r = 0.22 to 0.40). Similarly, DJ40 eccentric mean force had a much larger difference between the high and low HDEC groups than DJ20 (d = 1.11 vs. 0.51). These findings suggest DJ RSI from either height may be used as a proxy for HDEC ability, while DJ kinetic analyses should use a higher height to distinguish those with a better capacity to generate eccentric braking forces under increased eccentric loading demands.HIGHLIGHTS Players with greater drop jump reactive strength index (RSI) demonstrated superior horizontal deceleration ability.Drop jump RSI had a greater association with the early compared to the late horizontal deceleration sub-phase.Of the drop jump kinetic variables examined, concentric mean force had the largest associations with horizontal deceleration ability.

Jumping in Ballet: A Systematic Review of Kinetic and Kinematic Parameters

AIMS

Understanding the biomechanics of jumping in ballet dancers provides an opportunity to optimize performance and mitigate injury risk. This systematic review aimed to summarize research investigating kinetics and kinematics of jumping in ballet dancers.

METHODS

PubMed (MEDLINE), SPORTDiscus, and Web of Science were systematically searched for studies published before December 2020. Studies were required to investigate dancers specializing in ballet, assess kinetics or kinematics during take-off or landing, and be published in English.

RESULTS

A total of 3,781 articles were identified, of which 29 met the inclusion criteria. Seven studies investigated take-off (kinetics: n = 6; kinematics: n = 4) and 23 studies investigated landing (kinetics: n = 19; kinematics: n = 12). Included articles were categorized into six themes: Activity Type (n = 10), Environment and Equipment (n = 10), Demographics (n = 8), Physical Characteristics (n = 3), Injury Status (n = 2), and Skill Acquisition and Motor Control (n = 1). Peak landing vertical ground reaction force (1.4-9.6 times body weight) was most commonly reported. Limited evidence suggests greater ankle involvement during the take-off of ballet jumps compared to countermovement jumps. There is also limited evidence indicating greater sagittal plane joint excursions upon landing in ballet dancers compared to non-dancers, primarily through a more extended lower extremity at initial contact. Only 4 articles investigated male ballet dancers, which is a notable gap in the literature.

CONCLUSIONS

The findings of this review can be used by dance science and medicine practitioners to improve their understanding of jumping in ballet dancers.

Establishing the Noise: Interday Ecological Reliability of Countermovement Jump Variables in Professional Rugby Union Players

ABSTRACT

Howarth, DJ, Cohen, DD, McLean, BD, and Coutts, AJ. Establishing the noise: interday ecological reliability of countermovement jump variables in professional rugby union players. J Strength Cond Res XX(X): 000-000, 2021-The purpose of this study was to examine the interday "ecological" reliability of a wide range of ground reaction force-derived countermovement jump (CMJ) variables. Thirty-six male, professional rugby union players performed 3 CMJs on 4 separate days over an 8-day period during the first week of preseason. We calculated reliability for 86 CMJ variables across 5 interday combinations using 2 criteria: mean output across 3 jump trials (Mean3) and single output from the highest jump (BestJH). Interday coefficient of variation (CV) of the 86 variables in each CMJ phase, for Mean3 and BestJH, respectively, ranged between concentric = 2-11% and 2-13%; eccentric = 1-45% and 1-107%; and landing = 4-32% and 6-45%. Mean3 interday CV was lower in all 86 variables across every interday combination, compared with BestJH. CVs were lower in our cohort than previous studies, particularly for eccentric phase variables. There was no meaningful difference between interday conditions, suggesting any 2-day combination conducted within the first 8 days of preseason, represents a measure of "noise." We did not apply arbitrary reliability "cut-offs" used in previous work (e.g., CV <10%); therefore, our analysis provides reference reliability for a wide range of CMJ variables. However, we recommend that practitioners assess reliability in their athletes, as it is likely to be environment, protocol, and cohort specific.

Injury epidemiology in professional ballet: a five-season prospective study of 1596 medical attention injuries and 543 time-loss injuries

OBJECTIVES

To describe the incidence rate, severity, burden and aetiology of medical attention and time-loss injuries across five consecutive seasons at a professional ballet company.

METHODS

Medical attention injuries, time-loss injuries and dance exposure hours of 123 professional ballet dancers (women: n=66, age: 28.0±8.3 years; men: n=57, age: 27.9±8.5 years) were prospectively recorded between the 2015/2016 and 2019/2020 seasons.

RESULTS

The incidence rate (per 1000 hours) of medical attention injury was 3.9 (95% CI 3.3 to 4.4) for women and 3.1 (95% CI 2.6 to 3.5) for men. The incidence rate (per 1000 hours) of time-loss injury was 1.2 (95% CI 1.0 to 1.5) for women and 1.1 (95% CI 0.9 to 1.3) for men. First Soloists and Principals experienced between 2.0-2.2 additional medical attention injuries per 1000 hours and 0.9-1.1 additional time-loss injuries per 1000 hours compared with Apprentices (p≤0.025). Further, intraseason differences were observed in medical attention, but not time-loss, injury incidence rates with the highest incidence rates in early (August and September) and late (June) season months. Thirty-five per cent of time-loss injuries resulted in over 28 days of modified dance training. A greater percentage of time-loss injuries were classified as overuse (women: 50%; men: 51%) compared with traumatic (women: 40%; men: 41%).

CONCLUSION

This is the first study to report the incidence rate of medical attention and time-loss injuries in professional ballet dancers. Incidence rates differed across company ranks and months, which may inform targeted injury prevention strategies.

The prediction of Metabolic Syndrome alterations is improved by combining waist circumference and handgrip strength measurements compared to either alone

Background

Adiposity is a major component of the metabolic syndrome (MetS), low muscle strength has also been identified as a risk factor for MetS and for cardiovascular disease. We describe the prevalence of MetS and evaluate the relationship between muscle strength, anthropometric measures of adiposity, and associations with the cluster of the components of MetS, in a middle-income country.

Methods

MetS was defined by the International Diabetes Federation criteria. To assess the association between anthropometric variables (waist circumference (WC), waist-to-hip ratio (W/H), body mass index (BMI)), strength (handgrip/kg bodyweight (HGS/BW)) and the cluster of MetS, we created a MetS score. For each alteration (high triglycerides, low HDLc, dysglycemia, or high blood pressure) one point was conferred. To evaluate the association an index of fat:muscle and MetS score, participants were divided into 9 groups based on combinations of sex-specific tertiles of WC and HGS/BW.

Results

The overall prevalence of MetS in the 5,026 participants (64% women; mean age 51.2 years) was 42%. Lower HGS/BW, and higher WC, BMI, and W/H were associated with a higher MetS score. Amongst the 9 HGS/BW:WC groups, participants in the lowest tertile of HGS/BW and the highest tertile of WC had a higher MetS score (OR = 4.69 in women and OR = 8.25 in men;p < 0.01) compared to those in the highest tertile of HGS/BW and in the lowest tertile of WC.

Conclusion

WC was the principal risk factor for a high MetS score and an inverse association between HGS/BW and MetS score was found. Combining these anthropometric measures improved the prediction of metabolic alterations over either alone.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01256-z.

Drill design using the 'control-chaos continuum': Blending science and art during return to sport following knee injury in elite football

Establishing the level of risk, planning and adapting the return to sport (RTS) process following a complex knee injury involves drawing on a combination of relevant high-quality evidence and practitioner experience. On-pitch rehabilitation is a critical element of this process, providing an effective transition from rehabilitation to team training. The 'control-chaos continuum' (CCC) is an adaptable framework for on-pitch rehabilitation moving from high control to high chaos, progressively increasing running load demands and incorporating greater perceptual and neurocognitive challenges within sport-specific drills. Drills are a key element of the CCC, and are designed to ensure specificity, ecological validity and maintaining player interest. We showcase drill progression through the phases of the CCC, highlighting the use of constraints to create drills that incorporate the physical, technical, tactical and injury-specific needs of the player. We also provide recommendations to help practitioners create training session content using the CCC to help replicate the demands of team training within their own environment.

Does Muscle-Tendon Unit Structure Predispose to Hamstring Strain Injury During Running? A Critical Review

Hamstring strain injury (HSI) remains the most common muscle injury in high-intensity running in humans. The majority of acute HSI occur specifically within the proximal region of the long head of biceps femoris and there is a sustained interest among researchers in understanding the factors that predispose to HSI. The present critical review describes the current understanding of biceps femoris long head (BFlh) structural features that might influence strain injury risk. Inter-individual differences in muscle-tendon architecture and interactions, muscle fiber type and region-specific innervation are likely to influence biceps femoris long head injury risk and might inform why some individuals are at an increased risk of sustaining a HSI during running. However, more research is needed, with future studies focusing on prospective data acquisition, improved computer simulations and direct imaging techniques to better understand the relationship between structural features, hamstring muscle function, and injury risk.

Physical preparation and return to performance of an elite female football player following ACL reconstruction: a journey to the FIFA Women's World Cup

ACL injuries are among the most severe knee injuries in elite sport, with a high injury burden and re-injury risk. Despite extensive literature on the injury and the higher incidence of injury and re-injury in female athletes, there is limited evidence on the return to sport (RTS) of elite female football players following ACL reconstruction (ACLR). RTS is best viewed on a continuum aligning the recovery and rehabilitation process with the ultimate aim — a return to performance (RTP_erf). We outline the RTS and RTP_erf of an elite female football player following ACLR and her journey to the FIFA Women’s World Cup, including the gym-based physical preparation and the on-pitch/sports-specific reconditioning. We used the ‘control–chaos continuum’ as a framework for RTS, guiding a return above pre-injury training load demands while considering the qualitative nature of movement in competition. We then implemented the ‘RTP_erf pathway’ to facilitate a return to team training, competitive match play and a RTP_erf. Objective information, clinical reasoning and shared decision-making contributed to this process and helped the player to reach her goal of representing her country at the FIFA Women’s World Cup.

Managing the return to sport of the elite footballer following semimembranosus reconstruction

Hamstring strains are the most common injury in elite football and typically occur during high-speed running. Despite its important contribution to power production in the late swing phase, injury to the semimembranosus (SM) is less common than to the biceps femoris, but may involve the free tendon and depending on the degree of retraction, warrant surgical repair. Few case reports detail clinical reasoning, supported by objective data during rehabilitation in elite footballers, and none have described the return to sport (RTS) process following this type of hamstring injury. In this article, we outline the management and RTS of an English Premier League (EPL) footballer who suffered a high-grade SM proximal tendon tear during training. Due to the degree of retraction of the free tendon, the player underwent surgical reconstruction at the recommendation of an orthopaedic surgeon. Early physiotherapy care, nutritional support, on- and off-pitch injury-specific reconditioning and global athletic development are outlined, alongside strength and power diagnostic and global positioning systems data, assessment of pain, player feedback and MRI informed clinical reasoning and shared decision-making during the RTS process. 18 weeks post-surgery the player returned to team training, transferring to a new club 3 weeks later. 2.5 years post RTS, the player remains free of re-injury playing regularly in the EPL.

Can Countermovement Jump Neuromuscular Performance Qualities Differentiate Maximal Horizontal Deceleration Ability in Team Sport Athletes?

This investigation aimed to determine the countermovement jump (CMJ) neuromuscular performance (NMP) qualities that differentiate between athletes with high or low horizontal deceleration ability. Twenty-seven male university team sport athletes performed a CMJ on vertical axis force plates and a maximal horizontal deceleration following a 20 m maximal horizontal sprint acceleration. The instantaneous velocity throughout the maximal horizontal deceleration test was measured using a radar device. The deceleration ability was evaluated using the average deceleration (HDEC, m·s-2) and change in momentum-referred to as the horizontal braking impulse (HBI, N·s·kg-1). Participants were dichotomised into high and low HDEC and HBI according to a median-split analysis, and CMJ variables calculated for the overall eccentric, eccentric-deceleration and concentric phases. When horizontal deceleration ability was defined by HDEC, the CMJ concentric (effect size (ES) = 0.95) and eccentric (ES = 0.72) peak forces were the variables with the largest difference between groups. However, when defined using HBI, the largest difference was the concentric (ES = 1.15) and eccentric (ES = -1.00) peak velocities. Only the concentric mean power was significantly different between the high and low groups for both HDEC (ES = 0.85) and HBI (ES = 0.96). These findings show that specific eccentric and concentric NMP qualities may underpin the horizontal deceleration abilities characterised by HDEC and HBI. Specific NMP training interventions may be beneficial to target improvements in either of these measures of horizontal deceleration abilities.

Physical preparation and return to sport of the football player with a tibia-fibula fracture: applying the 'control-chaos continuum'

Contact in elite football can result in severe injury such as traumatic fracture. Limited information exists regarding the rehabilitation and return to sport (RTS) of these injuries especially in elite football. We outline the RTS of an elite English Premier League footballer following a tibia-fibula fracture including gym-based physical preparation and the use of 'control-chaos continuum' as a framework for on-pitch sport-specific conditioning, development of technical skills while returning the player to pre-injury chronic running loads considering the qualitative nature of movement in competition. Strength and power diagnostics were used to back up clinical reasoning and decision-making throughout rehabilitation and the RTS process. The player returned to full team training after 7.5 months, completed 90 min match-play after 9 months and remains injury-free 11 months post-RTS.

A comparison of the isometric force fatigue-recovery profile in two posterior chain lower limb tests following simulated soccer competition

Aim

To evaluate the reliability of isometric peak force (IPF) in a novel “long-length” 90°Hip:20°Knee (90:20) strength test and to compare the simulated soccer match induced fatigue-recovery profile of IPF in this test with that of an isometric 90°Hip:90°Knee (90:90) position test.

Methods

Twenty semi-professional soccer players volunteered for the study of which 14 participated in the first part of the study which assessed 90:20 reliability (age = 21.3 ± 2.5 years, height = 1.79 ± 0.07 m, body mass = 73.2 ± 8.8 kg), while 17 completed the second part of the study evaluating fatigue-recovery (age 21.2±2.4 yrs., height = 180 ± 0.09 m, body mass 73.8 ± 8.9 kg). We evaluated the inter-session reliability of IPF in two 90:20 test protocols (hands on the wall (HW); and hands on chest (HC)) both performed on two occasions, 7 days apart. We then assessed 90:20 (HC) and 90:90 IPF immediately before (PRE) and after (POST) after a simulated soccer match protocol (BEAST90mod) and 48 (+48 h) and 72 hours (+72 h) later.

Results

Part one: the 90:20 showed moderate to high overall reliability (CV’s of 7.3% to 11.0%) across test positions and limbs. CV’s were lower in the HW than HC in the dominant (7.3% vs 11.0%) but the opposite happened in the non-dominant limb where CV’s were higher in the HW than HC (9.7% vs 7.3%). Based on these results, the HC position was used in part two of the study. Part two: 90:20 and 90:90 IPF was significantly lower POST compared to PRE BEAST90mod across all testing positions (p<0.001). IPF was significantly lower at +48 h compared to PRE in the 90:20 in both limbs (Dominant: p<0.01,Non-dominant: p≤0.05), but not in the 90:90. At +72 h, IPF was not significantly different from PRE in either test.

Conclusions

Simple to implement posterior IPF tests can help to define recovery from competition and training load in football and, potentially, in other multiple sprint athletes. Testing posterior chain IPF in a more knee extended 90:20 position may provide greater sensitivity to fatigue at 48 h post simulated competition than testing in the 90:90 position, but also may require greater degree of familiarization due to more functional testing position.

Survey of knowledge for diagnosing and managing prediabetes in Latin-America: cross-sectional study

BACKGROUND

Prediabetes has been proposed as a risk factor for the development of type 2 diabetes mellitus (DM2) and cardiovascular disease (CVD). Despite the clinical importance of prediabetes, little is known about the level of knowledge, beliefs and barriers to screening and treating prediabetes amongst care health providers in Latin America. The aim of the present survey was to evaluate the knowledge and beliefs about prediabetes amongst in Latin American health care providers.

METHODOLOGY

In a cross-sectional study, we adapted the written survey designed by the Johns Hopkins University group, and applied it to health care providers across Latin America during three meetings, in 2017, and with physicians from primary care centers in Bucaramanga, Colombia convened in 2017. The survey consisted of questions under four headings, diabetes screening, management of prediabetes, pharmacological treatment-metformin use, and demographic information. We perform a descriptive analysis to determine the differences in responses between different medical specialties.

RESULTS

The majority of the care providers that answered the survey were Colombian physicians, 54.5% of respondents had 10 years or more since completing their training and more women responded. Only 9.5% identified the 12 prediabetes risk factors described in the literature. The most common risk factor identified was a family history of diabetes, followed by overweight, a sedentary lifestyle and dyslipidemia, while ethnicity was the risk factor least commonly. 47.1% answered that laboratory tests to detect prediabetes are fasting glucose and HbA1C, 82.5% correctly identified fasting plasma glucose as the best test, 35.9% correctly responded that to the recommended weight loss goal is 5 to 7% and 49.1% that 150 min is considered the minimum level of physical activity per week. 78% agreed that the identification and treatment of prediabetes is important. 56% believed that patients with prediabetes progress more rapidly to diabetes and 40.6% considered that metformin could reduce the risk of diabetes in patients already diagnosed with prediabetes.

CONCLUSION

These results demonstrate that there are important gaps in the knowledge of the diagnosis, clinical implications and management of prediabetes amongst Latin America health providers.

The spectrum of the dyslipidemia in Colombia: The PURE study

BACKGROUND

Dyslipidemia is a major risk factor for cardiovascular diseases (CVD). Worldwide, a third of ischemic heart disease is due to abnormal cholesterol levels and it is the most common cause of cardiovascular deaths in Colombia. In Colombia, no representative, large-scale study has assessed the prevalence of dyslipidemia. The aim of the present analysis was to identify the magnitude of the problem in Colombia, a middle-income-country with large regional, geographic, and socio-economical differences.

MATERIAL AND METHODS

The sample comprised 6628 individuals aged 35 to 70 years (mean age 50.7 years, 64.1% women) residing in the four Colombian regions.

RESULTS

The overall prevalence of dyslipidemia was 87.7% and was substantially higher among participants older than 50 years, male, rural residents, and those with a lower level of education (66.8%), and with a lower income (66.4%). High non HDL-c was the most common abnormality (75.3%). The values of total cholesterol and non-HDL-cholesterol were higher in areas with the lowest health needs index than in the areas with intermediate and highest health need index, the isolated HDL-c value was much lower.

CONCLUSION

Colombia has a high prevalence of abnormalities of the lipid profile. The causes of the high rates of dyslipidemia were not well define in this study, but were more common in rural and poorer regions and among those with lower socio-economical status. Strategies to tackle the adverse lipid profile to reduce CVD are needed in Colombia, particularly in rural areas and among the areas with the higher health need index.

Strength-Endurance Training Reduces the Hamstrings Strength Decline Following Simulated Football Competition in Female Players

Hamstring strains are the most common injury in multiple sprint sports, with inadequate eccentric hamstring strength and fatigue identified as important risk factors. Resistance training interventions aimed at reducing injury risk typically focus on the development of maximum strength, while little is known about the impact of training on hamstring fatigue resistance. The present study compared the effects of strength endurance (SE) with a strength intervention (S) on the eccentric hamstring strength decline induced by a simulated soccer match. Twenty-one female soccer players were randomly assigned to a S group (n = 10) or a SE group (n = 11). Hamstrings and quadriceps isokinetic concentric and eccentric peak torque (PT) were assessed at 120°.s^-1 and hamstrings-to-quadriceps ratio (HEcc:QCon) calculated, pre- and immediately post a 90-min simulated match (BEAST90). This was repeated following a 7-week intervention of either three to five sets of 6RM leg curl and stiff-leg deadlift with 3-min inter-set rest (S), or the same exercises performed using three sets of 12–20 RM with 45–90 s inter-set rest (SE). At baseline, the simulated match led to significant declines in hamstrings eccentric peak torque (EccPT) in both groups in both dominant (D) and non-dominant (ND) legs [SE: (D: -15.5, ND: -15.6%), P = 0.001 to 0.016; S: (D: -12.3%, ND: -15.5%), P = 0.001 to 0.018]. After the 7-week intervention, we observed a group^∗intervention^∗match interaction such that there was no significant decline in EccPT in the SE group following the simulated match (D: 5.3%, ND: 2.0%), but there remained significant declines in the S group (D: -14.2%, ND: -15.5%, P = 0.018–0.001). Similarly, in the SE group, there was a significant decrease in the HEcc:QCon in D before (-14.2%, P = 0.007), but not after the training intervention, whereas declines were observed in the S group both at baseline, and following the intervention (D: -13.9%, ND: -15.6%, P = 0.045). These results demonstrate that SE training can reduce the magnitude of the EccPT decline observed during soccer competition. As inadequate eccentric strength and fatigue are both risk factors for hamstring injury, SE training should be considered along with the development of peak eccentric strength, as a component of programs aimed at reducing injury risk in multiple-sprint sports.

Temporal trends in muscular fitness of English 10-year-olds 1998-2014: An allometric approach

OBJECTIVES

To identify temporal trends in muscular fitness of English children using allometric scaling for height and weight to adjust for the influence of body size.

DESIGN

Repeated cross-sectional study.

METHODS

We measured; height, weight, standing broad-jump, handgrip, sit-ups and bent-arm hang in 10-year-old boys and girls from Chelmsford, England in: 2014 (n=306), 2008 (n=304) and 1998 (n=310). Physical activity was (PAQ-C) was assessed in 2008 and 2014. Muscular fitness was allometrically scaled for height and weight. We assessed temporal trends using General Linear Models (fixed factors: wave and sex) and reported effect sizes using partial eta squared (η_P²). We compared percentage change per year 1998-2008 with 2008-2014.

RESULTS

Ten-year-olds in 2014 were taller and heavier than in 2008 and 1998 but there were no differences in BMI. Compared with 2008, physical activity was lower in boys (η_P²=0.012) and girls (η_P²=0.27) assessed in 2014. There were significant main effects of wave for handgrip (η_P²=0.060), sit-ups (η_P²=0.120) and bent-arm hang (η_P²=0.204). Pairwise comparisons showed muscular fitness of both sexes was significantly lower in 2014 than in 1998. From 2008 to 2014 percent change per year in handgrip (1.6%) and sit-ups (3.9%) were greater than for the preceding decade (handgrip 0.6%, sit-ups 2.6%).

CONCLUSIONS

Downward temporal trends in muscular fitness appear independent of secular changes in body size. We found a decrease in self-reported physical activity concurrent with the accelerated declines in fitness from 2008 to 2014. These findings suggest the declines in children are not engaging in physical activities which support development of muscular fitness.

The Athletic Shoulder (ASH) test: reliability of a novel upper body isometric strength test in elite rugby players

Objectives

Lower limb isometric tests are used to assess strength and strength asymmetries and monitor reductions in muscle force that may contribute to loss of performance and increase injury risk. Isometric tests in the upper body may be appropriate to monitor neuromuscular performance of the shoulder joint in sports involving contact and overhead actions. The aim of this study was to determine the reliability of a novel upper body isometric strength test.

Methods

Eighteen elite rugby players (age 22.4±4.6 years; body mass 95.5±13.4 kg) were tested on consecutive days. Maximal isometric contractions using both limbs against a force platform were assessed at three angles of abduction (180°, ‘I’; 135°, ‘Y’ and 90°, ‘T’), in a prone lying position. To evaluate interday reliability, intraclass coefficients (ICC) were calculated for mean net peak force (NPF) and highest NPF achieved in any trial (peak NPF). Intratrial variability was assessed using coefficient of variation (CV), and the standard error of measurement (SEM) was used to calculate minimal detectable change (MDC).

Results

Interday reliability for NPF was excellent in all test positions (ICC 0.94–0.98). The test demonstrated high absolute reliability values (SEM 4.8–10.8) and interday measurement error was below 10% in all test positions (CV 5.0–9.9%) except for the non-dominant arm I-position (CV 11.3%). Minimum detectable change was between 13.2 and 25.9 N.

Conclusion

The Athletic Shoulder test demonstrated excellent reliability for each test position supporting its use as a reliable tool to quantify the ability to produce and transfer force across the shoulder girdle.

Physical fitness characteristics of Omani primary school children according to body mass index

BACKGROUND

There is evidence that children with high cardiorespiratory fitness and normal body mass index (BMI) have less risk of non-communicable diseases (NCDs), however limited research was undertaken in Omani children. Therefore the aims of the present study were to describe body composition and physical fitness of a large cohort of Omani school children of both genders, and to investigate the effects of weight status on physical fitness.

METHODS

Three hundred and fourteen Omani school children aged 9 to 10 years old took part in anthropometric assessments, body composition and fitness tests, including handgrip strength, the basketball chest pass, broad jump, 20-m sprint, four 10-m shuttle agility, 30-s sit-up, and multistage fitness test (MSFT).

RESULTS

Obese boys and girls performed worse than normal-weight children in sprint, agility and endurance. In addition, fitness measures in the overweight group and underweight groups were not significantly different from other groups, except a better handgrip strength and poorer MSFT in overweight compared to normal weight girls, and poorer agility performance in underweight girls compared to the three other groups.

CONCLUSIONS

Most fitness measures are lower in obese Omani children, which suggests that they will be more at risk of developing NCDs later in life.

Reducing mortality risk by targeting specific air pollution sources: Suva, Fiji

Health implications of air pollution vary dependent upon pollutant sources. This work determines the value, in terms of reduced mortality, of reducing ambient particulate matter (PM_2.5: effective aerodynamic diameter 2.5μm or less) concentration due to different emission sources. Suva, a Pacific Island city with substantial input from combustion sources, is used as a case-study. Elemental concentration was determined, by ion beam analysis, for PM_2.5 samples from Suva, spanning one year. Sources of PM_2.5 have been quantified by positive matrix factorisation. A review of recent literature has been carried out to delineate the mortality risk associated with these sources. Risk factors have then been applied for Suva, to calculate the possible mortality reduction that may be achieved through reduction in pollutant levels. Higher risk ratios for black carbon and sulphur resulted in mortality predictions for PM_2.5 from fossil fuel combustion, road vehicle emissions and waste burning that surpass predictions for these sources based on health risk of PM_2.5 mass alone. Predicted mortality for Suva from fossil fuel smoke exceeds the national toll from road accidents in Fiji. The greatest benefit for Suva, in terms of reduced mortality, is likely to be accomplished by reducing emissions from fossil fuel combustion (diesel), vehicles and waste burning.

Airborne ultrafine particles in a Pacific Island country: Characteristics, sources and implications for human exposure

The Pacific Islands carry a perception of having clean air, yet emissions from transport and burning activities are of concern in regard to air quality and health. Ultrafine particle number concentrations (PNCs), one of the best metrics to demonstrate combustion emissions, have not been measured either in Suva or elsewhere in the Islands. This work provides insight into PNC variation across Suva and its relationship with particle mass (PM) concentration and composition. Measurements over a short monitoring campaign provide a vignette of conditions in Suva. Ambient PNCs were monitored for 8 day at a fixed location, and mobile PNC sampling for two days. These were compared with PM concentration (TSP, PM₁₀, PM_2.5, PM₁) and are discussed in relation to black carbon (BC) content and PM_2.5 sources, determined from elemental concentrations; for the October 2015 period and longer-term data. Whilst Suva City PM levels remained fairly low, PM_2.5 = 10-12 μg m^-3, mean PNC (1.64 ± 0.02 × 10⁴ cm^-3) was high compared to global data. PNCs were greater during mobile sampling, with means of 10.3 ± 1.4 × 10⁴ cm^-3 and 3.51 ± 0.07 × 10⁴ cm^-3 when travelling by bus and taxi, respectively. Emissions from road vehicles, shipping, diesel and open burning were identified as PM sources for the October 2015 period. Transport related ultrafine particle emissions had a significant impact on microscale ambient concentrations, with PNCs near roads being 1.5 to 2 times higher than nearby outdoor locations and peak PNCs occurring during peak traffic times. Further data, particularly on transport and wet-season exposures, are required to confirm results. Understanding PNC in Suva will assist in formulating effective air emissions control strategies, potentially reducing population exposure across the Islands and in developing countries with similar emission characteristics. Suva's PNC was high in comparison to global data; high exposures were related to transport and combustion emissions, which were also identified as significant PM_2.5 sources.

Strength and endurance training reduces the loss of eccentric hamstring torque observed after soccer specific fatigue

OBJECTIVES

To investigate the effect of two hamstring training protocols on eccentric peak torque before and after soccer specific fatigue.

PARTICIPANTS

Twenty-two university male soccer players.

DESIGN

Isokinetic strength tests were performed at 60°/s pre and post fatigue, before and after 2 different training interventions. A 45-min soccer specific fatigue modified BEAST protocol (M-BEAST) was used to induce fatigue. Players were randomly assigned to a 4 week hamstrings conditioning intervention with either a maximum strength (STR) or a muscle endurance (END) emphasis.

MAIN OUTCOME MEASURES

The following parameters were evaluated: Eccentric peak torque (EccPT), angle of peak torque (APT), and angle specific torques at knee joint angles of 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and 90°.

RESULTS

There was a significant effect of the M-BEAST on the Eccentric torque angle profile before training as well as significant improvements in post-fatigue torque angle profile following the effects of both strength and muscle endurance interventions.

CONCLUSIONS

Forty-five minutes of simulated soccer activity leads to reduced eccentric hamstring torque at longer muscle lengths. Short-term conditioning programs (4-weeks) with either a maximum strength or a muscular endurance emphasis can equally reduce fatigue induced loss of strength over this time period.

Muscle strength is associated with lower diastolic blood pressure in schoolchildren

Cardiorespiratory fitness (CRF) provides protection against the elevated blood pressure in overweight youth. Less is known regarding any similar protective effect of muscular fitness. We investigated how handgrip strength, an easy to implement measure of muscular strength, interacted with CRF and BMI to determine blood pressure in youth. We measured systolic (SBP) and diastolic (DBP) blood pressure, handgrip strength (HG), CRF and body mass index (BMI) in n=7329 10-16year-olds (47% girls). We defined elevated blood pressure as >91st percentile and Good HG as >33rd percentile. Participants were classified as Fit or Unfit and as Normal or Overweight/Obese based on international standards. The prevalence of elevated SBP was 23%, and 44% of participants had elevated DBP. In unfit participants Good HG was associated with lower SBP (z=0.41 (95%CI: 0.20-0.61) and DBP (z=0.29 (95%CI: 0.12-0.47). In Overweight/Obese participants, DBP was z=0.24 (95%CI: 0.14-0.34) lower in the Good (versus Low) HG group. Overweight/Obese participants with Good HG also had a 32% lower risk of elevated DBP (OR: 0.68, 95%CI: 0.57-0.82). This association was attenuated but remained important after adjusting for BMI (20% risk reduction, OR: 0.80, 95%CI: 0.63-1.01). Muscular fitness appears to play some protective role against the risk of elevated blood pressure; particularly for the more prevalent measure: elevated DBP (44%). Effects may be restricted to Overweight / Obese or unfit youth, who have an increased risk of elevated BP and also may be less likely to engage in traditional cardiorespiratory fitness training. Research to determine the effects of muscular fitness training on blood pressure is warranted in these subgroups.

Etiology of musculoskeletal injuries in amateur breakdancers

AIM

The aim of this study was to assess the incidence of musculoskeletal injuries in breakdancers and investigate the association with training habits.

METHODS

Forty-six males and sixteen females completed a questionnaire regarding their training and competition habits (frequency, warm-up and stretching, strength training, protective equipment, move types and supervision) and the musculoskeletal injuries sustained as a result of breakdancing in the previous 12 months. The effects of training habits and sex on injury rates were analyzed by a Mann-Whitney Test and a Kruskal-Wallis Test, while a stepwise linear regression analysis assessed the link between injury rates and quantitative risk factors.

RESULTS

The injury rate was 4.02 injuries per 1000 h, with no significant difference between males and females (P>0.05). The main injuries affected were the knee (23.4%) and wrist (15.3%), and females were characterized by a significantly greater number of finger injuries and a lower number of shoulder injuries that males (P<0.05). In addition, of all the factors evaluated, only the amount of time spent performing breakdance training showed a significant association with injury rate (P<0.05).

CONCLUSION

These results suggest that interventions should focus on protecting specific body parts and improving training quality and recovery.

Quantification of the relative age effect in three indices of physical performance

The relative age effect (RAE) describes the relationship between an individual's birth month and their level of attainment in sports. There is a clustering of birth dates just after the cutoff used for selection in age-grouped sports, and it is hypothesized that such relatively older sportspeople may enjoy maturational and physical advantages over their younger peers. There is, however, little empirical evidence of any such advantage. This study investigated whether schoolchildren's physical performance differed according to which quarter of the school year they were born in. Mass, stature, body mass index, cardiorespiratory fitness, strength, and power were measured in 10 to 16 year olds (n = 8,550, 53% male). We expressed test performance as age- and sex-specific z-scores based on reference data with age rounded down to the nearest whole year and also as units normalized for body mass. We then compared these values between yearly birth quarters. There were no significant main effects for differences in anthropometric measures in either sex. Girls born in the first quarter of the school year were significantly stronger than those born at other times when handgrip was expressed as a z-score. As z-scores, all measures were significantly higher in boys born in either the first or second yearly quarters. Relative to body mass, cardiorespiratory fitness was higher in boys born in the first quarter and power was higher in those born in the second quarter. The RAE does not appear to significantly affect girls' performance test scores when they are expressed as z-score or relative to body mass. Boys born in the first and second quarters of the year had a significant physical advantage over their relatively younger peers. These findings have practical bearing if coaches use fitness tests for talent identification and team selection. Categorizing test performance based on rounded down values of whole-year age may disadvantage children born later in the selection year. These relatively younger children may be less to gain selection for teams or training programmes.