The Role of Musculoskeletal Training During Return to Performance Following Relative Energy Deficiency in Sport.

BACKGROUND: Relative energy deficiency in sport (REDs) is a condition that is associated with negative health and performance outcomes in athletes. Insufficient energy intake relative to exercise energy expenditure, resulting in low energy availability, is the underlying cause, which triggers numerous adverse physiological consequences including several associated with musculoskeletal (MSK) health and neuromuscular performance. PURPOSE: This commentary aims to (1) discuss the health and performance implications of REDs on the skeletal and neuromuscular systems and (2) examine the role that MSK training (ie, strength and plyometric training) during treatment and return to performance following REDs might have on health and performance in athletes, with practical guidelines provided. CONCLUSIONS: REDs is associated with decreases in markers of bone health, lean body mass, maximal and explosive strength, and muscle work capacity. Restoration of optimal energy availability, mainly through an increase in energy intake, is the primary goal during the initial treatment of REDs with a return to performance managed by a multidisciplinary team of specialists. MSK training is an effective nonpharmacological component of treatment for REDs, which offers multiple long-term health and performance benefits, assuming the energy needs of athletes are met as part of their recovery. Supervised, prescribed, and gradually progressive MSK training should include a combination of resistance training and high-impact plyometric-based exercise to promote MSK adaptations, with an initial focus on achieving movement competency. Progressing MSK training exercises to higher intensities will have the greatest effects on bone health and strength performance in the long term.

Do Exercise-Based Prevention Programs Reduce Injury in Endurance Runners? A Systematic Review and Meta-Analysis.

BACKGROUND: Endurance running is a popular sport and recreational activity yet is associated with a high prevalence of injury. Running related injuries (RRIs) are a leading cause of drop-out and represent a substantial financial burden to runners and healthcare services. There is clear evidence for the use of exercise-based injury prevention programs in games-based and youth sport settings, yet the research investigating the use of exercise to reduce injury risk in endurance runners has not been adequately reviewed recently. OBJECTIVES: The aim of this review and meta-analysis was to systematically summarize the current research that has investigated the effect of exercise-based prevention programs and their state of supervision on the risk of RRIs in endurance runners. METHODS: Three databases were searched for relevant studies. Selection and review were completed by two independent reviewers using the following inclusion criteria: (1) study population used endurance running training for health, occupational, or performance outcome(s); (2) participants performed running as their main form of exercise (> 50% of their total training time); (3) study was a randomized controlled trial; (4) a non-running-based exercise intervention was used; (5) a running-only or placebo exercise control group was included; (6) injury rate or incidence was reported; (7) injuries were recorded prospectively alongside the exercise training. Two meta-analyses were conducted using random-effects models, one based on log risk ratio and one based on log incidence rate ratio. The Cochrane Risk of Bias Assessment Tool 2 was used to evaluate the quality of studies and the Grading of Recommendations Assessment, Development and Evaluations approach was employed to grade the certainty of evidence. RESULTS: A total of nine articles containing 1904 participants were included in analysis. Overall pooled results showed no significant differences between intervention and control groups in injury risk (z = - 1.60; p = 0.110) and injury rate (z = - 0.98; p = 0.329), while a post hoc analysis evaluating supervised interventions only showed that injury risk was significantly lower in the intervention group compared to the control group (z = - 3.75, p < 0.001). Risk of bias assessment revealed that seven studies included in the analysis were of low quality. CONCLUSIONS: Exercise-based interventions do not appear to reduce the risk and rate of running-related injuries. Supervision may be essential for exercise-based intervention programs to reduce risk of RRIs, possibly due to increased compliance. Studies with more robust designs that include supervised exercise interventions should be prioritized in the future. TRIAL REGISTRY: Clinical Trial Registration: PROSPERO CRD42021211274.

The effect of a prior eccentric lowering phase on concentric neuromechanics during multiple joint resistance exercise in older adults.

Aging involves a marked decline in physical function and especially muscle power. Thus, optimal resistance exercise (RE) to improve muscle power is required for exercise prescription. An eccentric lowering phase immediately before a concentric lift (ECC-CON) may augment concentric power production, due to various proposed mechanisms (e.g., elastic recoil, pre-activation, stretch reflex, contractile history), when compared with a concentric contraction alone (CON-Only). This study compared the effect of a prior eccentric lowering phase on older adult concentric power performance (ECC-CON vs. CON-Only) during a common multiple joint isoinertial RE (i.e., leg press) with a range of loads. Twelve healthy older adult males completed two measurement sessions, consisting of ECC-CON and CON-Only contractions, performed in a counterbalanced order using 20-80% of one repetition maximum [% 1RM] loads on an instrumented isoinertial leg press dynamometer that measured power, force, and velocity. Muscle activation was assessed with surface electromyography (sEMG). For mean power ECC-CON>CON-Only, with a pronounced effect of load on the augmentation of power by ECC-CON (+19 to +55%, 35-80% 1RM, all p < 0.032). Similarly, for mean velocity ECC-CON>CON-Only, especially as load increased (+15 to 54%, 20-80% 1RM, all p < 0.005), but mean force showed more modest benefits of ECC-CON (+9 to 14%, 50-80% 1RM, all p < 0.05). In contrast, peak power and velocity were similar for ECC-CON and CON-Only with all loads. Knee and hip extensor sEMG were similar for both types of contractions. In conclusion, ECC-CON contractions produced greater power, and velocity performance in older adults than CON-Only and may provide a superior stimulus for chronic power development.

High-impact jumping mitigates the short-term effects of low energy availability on bone resorption but not formation in regularly menstruating females: A randomized control trial.

Low energy availability (LEA) is prevalent in active individuals and negatively impacts bone turnover in young females. High-impact exercise can promote bone health in an energy efficient manner and may benefit bone during periods of LEA. Nineteen regularly menstruating females (aged 18-31 years) participated in two three-day conditions providing 15 (LEA) and 45 kcals kg fat-free mass-1 day-1 (BAL) of energy availability, each beginning 3 ± 1 days following the self-reported onset of menses. Participants either did (LEA+J, n = 10) or did not (LEA, n = 9) perform 20 high-impact jumps twice per day during LEA, with P1NP, ß-CTx (circulating biomarkers of bone formation and resorption, respectively) and other markers of LEA measured pre and post in a resting and fasted state. Data are presented as estimated marginal mean ± 95% CI. P1NP was significantly reduced in LEA (71.8 ± 6.1-60.4 ± 6.2 ng mL-1 , p < 0.001, d = 2.36) and LEA+J (93.9 ± 13.4-85.2 ± 12.3 ng mL-1 , p < 0.001, d = 1.66), and these effects were not significantly different (time by condition interaction: p = 0.269). ß-CTx was significantly increased in LEA (0.39 ± 0.09-0.46 ± 0.10 ng mL-1 , p = 0.002, d = 1.11) but not in LEA+J (0.65 ± 0.08-0.65 ± 0.08 ng mL-1 , p > 0.999, d = 0.19), and these effects were significantly different (time by condition interaction: p = 0.007). Morning basal bone formation rate is reduced following 3 days LEA, induced via dietary restriction, with or without high-impact jumping in regularly menstruating young females. However, high-impact jumping can prevent an increase in morning basal bone resorption rate and may benefit long-term bone health in individuals repeatedly exposed to such bouts.

Lumbar spine bone mineral adaptation: cricket fast bowlers versus controls.

Elite adult male fast bowlers have high lumbar spine bone mineral, particularly on the contralateral side to their bowling arm. It is thought that bone possesses its greatest ability to adapt to loading during adolescence, but it is unknown at what age the greatest changes in lumbar bone mineral and asymmetry develops in fast bowlers. Objectives: This study aims to evaluate the adaptation of the lumbar vertebrae in fast bowlers compared to controls and how this is associated with age. Methods: 91 male fast bowlers and 84 male controls aged 14-24 years had between one and three annual anterior-posterior lumbar spine dual-energy-X-ray absorptiometry scans. Total (L1-L4) and regional ipsilateral and contralateral L3 and L4 (respective to bowling arm) bone mineral density and content (BMD/C) were derived. Multilevel models examined the differences in lumbar bone mineral trajectories between fast bowlers and controls. Results: At L1-L4 BMC and BMD, and contralateral BMD sites, fast bowlers demonstrated a greater negative quadratic pattern to their accrual trajectories than controls. Fast bowlers had greater increases in BMC in L1-L4 between 14 and 24 years of 55% compared with controls (41%). Within vertebra, asymmetry was evident in all fast bowlers and increased by up to 13% in favour of the contralateral side. Conclusions: Lumbar vertebral adaptation to fast bowling substantially increased with age, particularly on the contralateral side. The greatest accrual was during late adolescence and early adulthood, which may correspond with the increasing physiological demands of adult professional sport.

Bone health and asymmetry in elite female cricketers.

The aim of this study is to determine if bone mineral density (BMD) and bone asymmetry differs between female cricket fast bowlers, spin bowlers and batters. BMD was determined at the total body, lumbar spine, and proximal femurs in 12 fast bowlers, 13 batters and 11 spin bowlers from pre-season DXA scans. High Z-scores at the total body, lumbar spine, and proximal femur were observed in all cricketers (mean Z-scores: +1.4 to +3.3) compared with a general age matched reference population. Fast bowlers had significantly greater BMD on the contralateral side of the lumbar spine compared with the ipsilateral side (p = 0.001, 5.9-12.1%). No asymmetry was found between hips in all groups. All cricket positions demonstrated high BMD at all measured sites. The lumbar spine of fast bowlers is asymmetric, with significantly greater BMD on the contralateral side of the spine, particularly at L4, possibly in response to the asymmetric lumbar loading patterns observed in bowling.HighlightsElite female cricketers demonstrate high BMD at total body, lumbar spine and proximal femur sites, regardless of playing position compared with a general age and ethnic group matched reference population.Fast bowlers have greater BMD on the contralateral (opposite bowling arm) side of the lumbar spine compared with the ipsilateral side, while a symmetrical pattern was observed in spin bowlers and batters.No asymmetry in BMD or section modulus between hips was observed at any proximal femur site for any cricket position.

Activity specific areal bone mineral density is reduced in athletes with stress fracture and requires profound recovery time: A study of lumbar stress fracture in elite cricket fast bowlers.

OBJECTIVES: The aims of this study were to determine whether lumbar areal bone mineral density differed between cricket fast bowlers with and without lumbar stress fracture, and whether bone mineral density trajectories differed between groups during rehabilitation. DESIGN: Cross-sectional and cohort. METHODS: 29 elite male fast bowlers received a post-season anteroposterior lumbar dual-energy X-ray absorptiometry scan and a lumbar magnetic resonance imaging scan to determine stress fracture status. Participants were invited for three additional scans across the 59 weeks post baseline or diagnosis of injury. Bone mineral density was measured at L1 - L4 and ipsilateral and contralateral L3 and L4 sites. Independent-sample t-tests determined baseline differences in bone mineral density and multilevel models were used to examine differences in bone mineral density trajectories over time between injured and uninjured participants. RESULTS: 17 participants with lumbar stress fracture had lower baseline bone mineral density at L1 - L4 (7.6 %, p = 0.034) and contralateral sites (8.8-10.4 %, p = 0.038-0.058) than uninjured participants. Bone mineral density at all sites decreased 1.9-3.0 % by 20-24 weeks before increasing to above baseline levels by 52 weeks post injury. CONCLUSIONS: Injured fast bowlers had lower lumbar bone mineral density at diagnosis that decreased following injury and did not return to baseline until up to a year post-diagnosis. Localised maladaptation of bone mineral density may contribute to lumbar stress fracture. Bone mineral density loss following injury may increase risk of recurrence, therefore fast bowlers require careful management when returning to play.

Strong, steady and straight: UK consensus statement on physical activity and exercise for osteoporosis.

Exercise and physical activity can improve bone strength and the risk of falls, which may offer benefits in the prevention and management of osteoporosis. However, uncertainty about the types of exercise that are safe and effective instigates lack of confidence in people with osteoporosis and health professionals. Existing guidelines leave some questions unresolved. This consensus statement aimed to determine the physical activity and exercise needed to optimise bone strength, reduce fall and fracture risk, improve posture and manage vertebral fracture symptoms, while minimising potential risks in people with osteoporosis. The scope of this statement was developed following stakeholder consultation. Meta-analyses were reviewed and where evidence was lacking, individual studies or expert opinion were used to develop recommendations. A multidisciplinary expert group reviewed evidence to make recommendations, by consensus when evidence was not available. Key recommendations are that people with osteoporosis should undertake (1) resistance and impact exercise to maximise bone strength; (2) activities to improve strength and balance to reduce falls; (3) spinal extension exercise to improve posture and potentially reduce risk of falls and vertebral fractures. For safety, we recommend avoiding postures involving a high degree of spinal flexion during exercise or daily life. People with vertebral fracture or multiple low trauma fractures should usually exercise only up to an impact equivalent to brisk walking. Those at risk of falls should start with targeted strength and balance training. Vertebral fracture symptoms may benefit from exercise to reduce pain, improve mobility and quality of life, ideally with specialist advice to encourage return to normal activities. Everyone with osteoporosis may benefit from guidance on adapting postures and movements. There is little evidence that physical activity is associated with significant harm, and the benefits, in general, outweigh the risks.

Lumbar bone stress injuries and risk factors in adolescent cricket fast bowlers.

Cricket fast bowling is associated with a high prevalence of lumbar bone stress injuries (LBSI), especially in adolescent bowlers. This has not been sufficiently explained by risk factors identified in adult players. This study aimed to examine the incidence of LBSI in adolescent fast bowlers over a prospective study and potential risk factors. Forty asymptomatic male fast bowlers (aged 14-17 years) received baseline and annual lumbar dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) scans, and musculoskeletal and bowling workload assessment; 22 were followed up after one year. LBSI prevalence at baseline and annual incidence were calculated. Potential risk factors were compared between the injured and uninjured groups using T-tests with Hedges' g effect sizes. At baseline, 20.5% of participants had at least one LBSI. Subsequent LBSI incidence was 27.3 ± 18.6 injuries per 100 players per year (mean ± 95% CI). Injured bowlers were older on average at the beginning of the season preceding injury (16.8 versus 15.6 years, g = 1.396, P = 0.047). LBSI risk may coincide with increases in bowling workload and intensity as bowlers step up playing levels to more senior teams during late adolescence whilst the lumbar spine is immature and less robust.

Fast and ballistic contractions involve greater neuromuscular power production in older adults during resistance exercise.

PURPOSE: Neuromuscular power is critical for healthy ageing. Conventional older adult resistance training (RT) guidelines typically recommend lifting slowly (2-s; CONV), whereas fast/explosive contractions performed either non-ballistically (FAST-NB) or ballistically (FAST-B, attempting to throw the load) may involve greater acute power production, and could ultimately provide a greater chronic power adaptation stimulus. To compare the neuromechanics (power, force, velocity, and muscle activation) of different types of concentric isoinertial RT contractions in older adults. METHODS: Twelve active older adult males completed three sessions, each randomly assigned to one type of concentric contraction (CONV or FAST-NB or FAST-B). Each session involved lifting a range of loads (20-80%1RM) using an instrumented isoinertial leg press dynamometer that measured power, force, and velocity. Muscle activation was assessed with surface electromyography (sEMG). RESULTS: Peak and mean power were markedly different, according to the concentric contraction explosive intent FAST-B > FAST-NB > CONV, with FAST-B producing substantially more power (+ 49 to 1172%, P ≤ 0.023), force (+ 10 to 136%, P < 0.05) and velocity (+ 55 to 483%, P ≤ 0.025) than CONV and FAST-NB contractions. Knee and hip extensor sEMG were typically higher during FAST-B than CON (all P < 0.02) and FAST-NB (≤ 50%1RM, P ≤ 0.001). CONCLUSIONS: FAST-B contractions produced markedly greater power, force, velocity and muscle activation across a range of loads than both CONV or FAST-NB and could provide a more potent RT stimulus for the chronic development of older adult power.

Tackling Dementia: A Systematic Review of Interventions Based on Physical Activity.

BACKGROUND AND PURPOSE: Dementia prevalence is expected to increase dramatically with population aging. As a nonpharmacological therapy, physical activity is an appealing alternative to tackling aging and dementia. However, contradictions were found in previous studies. The aim of this systematic review is to gather the latest evidence of the effects of physical activity interventions on cognition and noncognitive functions of older people with dementia. METHODS: PubMed, Cochrane, and Web of Science databases were searched to identify relevant studies. We followed the PRISMA guidelines to identify randomized controlled trials that reported original findings of physical activity interventions on older people with dementia (≥65 years of age). These studies were published in English between January 1, 2009 and November 9, 2019. RESULTS: In total, 16 trials with 2085 participants were included in the review. Compared to baseline, cognitive function improved significantly in 2 studies, deteriorated in 3 studies, and remained stable in 11 studies. In the exercise relative to the control group, 5 studies showed no significant differences, 2 studies showed significantly greater deterioration in cognition, and 9 studies showed significantly greater improvement in cognition. However, most studies (n = 13.81%) had notable limitations (eg, with a high risk of bias, limited follow-up time, or unexplained high heterogeneity in their findings). Fourteen studies reported a positive impact on one or more areas of physical function, mobility, activities of daily living, depression levels, and behavioral/psychological symptoms of dementia. CONCLUSIONS: Physical activity interventions have a positive impact on physical function, mobility, and activities of daily living. However, the available evidence is insufficient to support the conclusion that physical activity improves cognitive function of older people with dementia.

Lumbar Bone Mineral Adaptation: The Effect of Fast Bowling Technique in Adolescent Cricketers.

INTRODUCTION: Localized bone mineral density (BMD) adaptation of the lumbar spine, particularly on the contralateral side to the bowling arm, has been observed in elite male cricket fast bowlers. No study has investigated this in adolescents, or the role of fast bowling technique on lumbar BMD adaptation. This study aims to investigate lumbar BMD adaptation in adolescent cricket fast bowlers, and its relationship with fast bowling technique. METHODS: Thirty-nine adolescent fast bowlers underwent anteroposterior dual x-ray absorptiometry scan of their lumbar spine. Hip, lumbopelvic and thoracolumbar joint kinematics, and vertical ground reaction kinetics were determined using three-dimensional motion capture and force plates. Significant partial (covariate: fat-free mass) and bivariate correlations of the technique parameters with whole lumbar (L1-L4) BMD and BMD asymmetry (L3 and L4) were advanced as candidate variables for multiple stepwise linear regression. RESULTS: Adolescent fast bowlers demonstrated high lumbar Z-Scores (+1.0; 95% confidence interval [CI], 0.7-1.4) and significantly greater BMD on the contralateral side of L3 (9.0%; 95% CI, 5.8%-12.1%) and L4 (8.2%; 95% CI, 4.9%-11.5%). Maximum contralateral thoracolumbar rotation and maximum ipsilateral lumbopelvic rotation in the period between back foot contact and ball release (BR), as well as contralateral pelvic drop at front foot contact, were identified as predictors of L1 to L4 BMD, explaining 65% of the variation. Maximum ipsilateral lumbopelvic rotation between back foot contact and BR, as well as ipsilateral lumbopelvic rotation and contralateral thoracolumbar side flexion at BR, were predictors of lumbar asymmetry within L3 and L4. CONCLUSIONS: Thoracolumbar and lumbopelvic motion are implicated in the etiology of the unique lumbar bone adaptation observed in fast bowlers whereas vertical ground reaction force, independent of body mass, was not. This may further implicate the osteogenic potential of torsional rather than impact loading in exercise-induced adaptation.

Incidence of bone stress injury is greater in competitive female distance runners with menstrual disturbances independent of participation in plyometric training.

Bone stress injury (BSI) is prevalent in female distance runners. Menstrual disturbances are associated with impaired bone health in endurance athletes. This study aimed to investigate the association between menstrual function and BSI and explore whether plyometric training may protect against BSI in individuals with menstrual disturbances. Competitive female distance runners (n = 183) aged 18-40 years were surveyed for training habits, menstrual function, and BSI, during the previous 12 months. Oligo/amenorrhoea during the previous 12 months (<9 menses) was deemed to indicate menstrual disturbance; hormonal contraceptive users and those previously diagnosed with a pathology that impacted menstrual function were excluded. BSI incidence rate was 2.25 (p = 0.02, 95% CI: 1.14-4.41) times greater in oligo/amenorrhoeic than eumenorrhoeic runners. BSI incidence rate was similar in oligo/amenorrhoeic and eumenorrhoeic runners that did plyometric training, but 3.78 (p = 0.001, 95% CI: 1.68-8.5) times greater in oligo/amenorrhoeic versus eumenorrhoeic runners that did not. However, the effect of plyometrics was non-significant (menstrual function × plyometric training interaction, p = 0.06; main effect, p = 0.89). Conventional plyometric training may not reduce BSI incidence in female distance runners, but menstrual disturbances and prolonged periods of low energy availability should be avoided.

Assessment of body composition in spinal cord injury: A scoping review.

The objective of this scoping review was to map the evidence on measurement properties of body composition tools to assess whole-body and regional fat and fat-free mass in adults with SCI, and to identify research gaps in order to set future research priorities. Electronic databases of PubMed, EMBASE and the Cochrane library were searched up to April 2020. Included studies employed assessments related to whole-body or regional fat and/or fat-free mass and provided data to quantify measurement properties that involved adults with SCI. All searches and data extractions were conducted by two independent reviewers. The scoping review was designed and conducted together with an expert panel (n = 8) that represented research, clinical, nutritional and lived SCI experience. The panel collaboratively determined the scope and design of the review and interpreted its findings. Additionally, the expert panel reached out to their professional networks to gain further stakeholder feedback via interactive practitioner surveys and workshops with people with SCI. The research gaps identified by the review, together with discussions among the expert panel including consideration of the survey and workshop feedback, informed the formulation of future research priorities. A total of 42 eligible articles were identified (1,011 males and 143 females). The only tool supported by studies showing both acceptable test-retest reliability and convergent validity was whole-body dual-energy x-ray absorptiometry (DXA). The survey/workshop participants considered the measurement burden of DXA acceptable as long as it was reliable, valid and would do no harm (e.g. radiation, skin damage). Practitioners considered cost and accessibility of DXA major barriers in applied settings. The survey/workshop participants expressed a preference towards simple tools if they could be confident in their reliability and validity. This review suggests that future research should prioritize reliability and validity studies on: (1) DXA as a surrogate 'gold standard' tool to assess whole-body composition, regional fat and fat-free mass; and (2) skinfold thickness and waist circumference as practical low-cost tools to assess regional fat mass in persons with SCI, and (3) females to explore potential sex differences of body composition assessment tools. Registration review protocol: CRD42018090187 (PROSPERO).

Tracking Within-Athlete Changes in Whole-Body Fat Percentage in Wheelchair Athletes.

PURPOSE: To evaluate the tracking of within-athlete changes in criterion measures of whole-body fat percentage (BF%; dual-energy X-ray absorptiometry) with skinfold thickness (Σ 4, 6, or 8) in wheelchair basketball players. METHODS: Dual-energy X-ray absorptiometry-derived whole BF% and Σ 4, 6, or 8 skinfolds were obtained at 5 time points over 15 months (N = 16). A linear mixed model with restricted maximum likelihood (random intercept, with identity covariance structure) to derive the within-athlete prediction error for predicting criterion BF% from Σ skinfolds was used. This prediction error allowed us to evaluate how well a simple measure of the Σ skinfolds could track criterion changes in BF %; that is, the authors derived the change in Σ skinfolds that would have to be observed in an individual athlete to conclude that a substantial change in criterion BF% had occurred. Data were log-transformed prior to analysis. RESULTS: The Σ 8 skinfolds was the most precise practical measure for tracking changes in BF%. For the monitoring of an individual player, a change in Σ 8 skinfolds by a factor of greater than 1.28 (multiply or divide by 1.28) is associated with a practically meaningful change in BF% (≥1 percentage point). CONCLUSIONS: The Σ 8 skinfolds can track changes in BF% within individuals with reasonable precision, providing a useful field monitoring tool in the absence of often impractical criterion measures.

Effects of Low Energy Availability on Bone Health in Endurance Athletes and High-Impact Exercise as A Potential Countermeasure: A Narrative Review.

Endurance athletes expend large amounts of energy in prolonged high-intensity exercise and, due to the weight-sensitive nature of most endurance sports, often practice periods of dietary restriction. The Female Athlete Triad and Relative Energy Deficiency in Sport models consider endurance athletes at high-risk for suffering from low energy availability and associated health complications, including an increased chance of bone stress injury. Several studies have examined the effects of low energy availability on various parameters of bone structure and markers of bone (re)modelling; however, there are differences in findings and research methods and critical summaries are lacking. It is difficult for athletes to reduce energy expenditure or increase energy intake (to restore energy availability) in an environment where performance is a priority. Development of an alternative tool to help protect bone health would be beneficial. High-impact exercise can be highly osteogenic and energy efficient; however, at present, it is rarely utilized to promote bone health in endurance athletes. Therefore, with a view to reducing the prevalence of bone stress injury, the objectives of this review are to evaluate the effects of low energy availability on bone health in endurance athletes and explore whether a high-impact exercise intervention may help to prevent those effects from occurring.

Cricket Fast Bowling Technique and Lumbar Bone Stress Injury.

INTRODUCTION: Lumbar bone stress injuries (LBSI) are the most prevalent injury in cricket. Although fast bowling technique has been implicated in the etiology of LBSI, no previous study has attempted to prospectively analyze fast bowling technique and its relationship to LBSI. The aim of this study was to explore technique differences between elite cricket fast bowlers with and without subsequent LBSI. METHODS: Kinematic and kinetic technique parameters previously associated with LBSI were determined for 50 elite male fast bowlers. Group means were compared using independent-samples t-tests to identify differences between bowlers with and without a prospective LBSI. Significant parameters were advanced as candidate variables for a binary logistic regression analysis. RESULTS: Of the 50 bowlers, 39 sustained a prospective LBSI. Significant differences were found between injured and noninjured bowlers in rear knee angle, rear hip angle, thoracolumbar side flexion angle, and thoracolumbar rotation angle at back foot contact; the front hip angle, pelvic tilt orientation, and lumbopelvic angle at front foot contact; and the thoracolumbar side flexion angle at ball release and the maximal front hip angle and ipsilateral pelvic drop orientation. A binary logistic model, consisting of rear hip angle at back foot contact and lumbopelvic angle at front foot contact, correctly predicted 88% of fast bowlers according to injury history and significantly increased the odds of sustaining an LBSI (odds ratio, 0.88 and 1.25, respectively). CONCLUSIONS: Lumbopelvic motion is implicated in the etiology of LBSI in fast bowling, with inadequate lumbopelvifemoral complex control as a potential cause. This research will aid the identification of fast bowlers at risk of LBSI, as well as enhancing coaching and rehabilitation of fast bowlers from LBSI.

High-Impact Exercise Increased Femoral Neck Bone Density With No Adverse Effects on Imaging Markers of Knee Osteoarthritis in Postmenopausal Women.

High-impact exercise can improve femoral neck bone mass but findings in postmenopausal women have been inconsistent and there may be concern at the effects of high-impact exercise on joint health. We investigated the effects of a high-impact exercise intervention on bone mineral density (BMD), bone mineral content (BMC), and section modulus (Z) as well as imaging biomarkers of osteoarthritis (OA) in healthy postmenopausal women. Forty-two women aged 55 to 70 years who were at least 12 months postmenopausal were recruited. The 6-month intervention consisted of progressive, unilateral, high-impact exercise incorporating multidirectional hops on one randomly assigned exercise leg (EL) for comparison with the contralateral control leg (CL). Dual-energy X-ray absorptiometry (DXA) was used to measure BMD, BMC, and Z of the femoral neck. Magnetic resonance imaging (MRI) of the knee joint was used to analyze the biochemical composition of articular cartilage using T2 relaxometry and to analyze joint pathology associated with OA using semiquantitative analysis. Thirty-five participants (61.7 ± 4.3 years) completed the intervention with a mean adherence of 76.8% ± 22.5%. Femoral neck BMD, BMC, and Z all increased in the EL (+0.81%, +0.69%, and +3.18%, respectively) compared to decreases in the CL (-0.57%, -0.71%, and -0.75%: all interaction effects p < 0.05). There was a significant increase in mean T2 relaxation times (main effect of time p = 0.011) but this did not differ between the EL and CL, indicating no global effect. Semiquantitative analysis showed high prevalence of bone marrow lesions (BML) and cartilage defects, especially in the patellofemoral joint (PFJ), with no indication that the intervention caused pathology progression. In conclusion, a high-impact exercise intervention that requires little time, cost, or specialist equipment improved femoral neck BMD with no negative effects on knee OA imaging biomarkers. Unilateral high-impact exercise is a feasible intervention to reduce hip fracture risk in healthy postmenopausal women. © 2019 American Society for Bone and Mineral Research.

Four decades of socio-economic inequality and secular change in the physical growth of Guatemalans.

OBJECTIVE: To investigate changes in socio-economic inequalities in growth in height, weight, BMI and grip strength in children born during 1955-1993 in Guatemala, a period of marked socio-economic-political change. DESIGN: We modelled longitudinal data on height, weight, BMI and hand grip strength using Super-Imposition by Translation and Rotation (SITAR). Internal Z-scores summarising growth size, timing and intensity (peak growth velocity, e.g. cm/year) were created to investigate inequalities by socio-economic position (SEP; measured by school attended). Interactions of SEP with date of birth were investigated to capture secular changes in inequalities. SETTING: Urban and peri-urban schools in the region of Guatemala City, Guatemala. PARTICIPANTS: Participants were 40 484 children and adolescents aged 3-19 years of Ladino and Maya ancestry (nobservations 157 067). RESULTS: The difference in height (SITAR size) between lowest and highest SEP decreased from -2·0 (95 % CI -2·2, -1·9) sd to -1·4 (95 % CI -1·5, -1·3) sd in males, and from -2·0 (95 % CI -2·1, -1·9) sd to -1·2 (95 % CI -1·3, -1·2) sd in females over the study period. Inequalities also reduced for weight, BMI and grip strength, due to greater secular increases in lowest-SEP groups. The puberty period was earlier and shorter in higher-SEP individuals (earlier SITAR timing and higher SITAR intensity). All SEP groups showed increases in BMI intensity over time. CONCLUSIONS: Inequality narrowed between the 1960s and 1990s. The lowest-SEP groups were still >1 sd shorter than the highest. Risks remain for reduced human capital and poorer population health for urban Guatemalans.