## Τρίτη, 7 Μαΐου 2019

### Sports Medicine

Principles of Motor Learning to Support Neuroplasticity After ACL Injury: Implications for Optimizing Performance and Reducing Risk of Second ACL Injury

"As ACL injury may alter intracortical facilitation [34] and depressed intracortical inhibition is correlated with decreased quadriceps voluntary activation capability [35], external focus training may provide a means to restore quadriceps muscle activity via increasing intracortical inhibition.

Authors' Reply to Valenzuela et al: Comment on: "Assessment of Skeletal Muscle Contractile Properties by Radial Displacement: The Case for Tensiomyography"

Comment on: "Assessment of Skeletal Muscle Contractile Properties by Radial Displacement: The Case for Tensiomyography"

Behavioral Correlates of Muscular Fitness in Children and Adolescents: A Systematic Review

### Background

Muscular fitness (MF) is considered a powerful marker of health, but the extent to which common health behaviors are associated with MF during childhood and adolescence is currently unclear.

### Objective

We conducted a systematic review of studies investigating associations between MF (i.e., strength/power, local muscular endurance) and physical activity, sedentary behaviors, and sleep in children and adolescents.

### Methods

A systematic search of six electronic databases was performed on 8 March, 2017. Search results were screened for relevance and studies conducted with children and adolescents (3–18 years) that explored associations between MF and physical activity, sedentary behavior, or sleep were considered eligible. Data were extracted and checked by a second author. The proportion of studies reporting a statistically significant association between each MF component and behavioral variables was calculated, and additional coding was conducted to account for risk of bias.

### Results

There was consistent evidence for a positive association between MF and physical activity. For both MF components, there was support for objectively measured physical activity, particularly for activity of vigorous intensity. Sports participation was also consistently linked with both MF components, whereas the association with active transport was inconsistent. For both MF components, associations with sedentary behaviors were inconsistent irrespective of measurement method, and the association between MF and sleep was considered uncertain.

### Conclusions

The available evidence supports a link between MF and physical activity, particularly for vigorous intensity activity and organized sports participation. Conversely, there is limited support for an association with sedentary behaviors, and more research exploring MF and sleep is required.

Weightlifting Overhead Pressing Derivatives: A Review of the Literature

### Abstract

This review examines the literature on weightlifting overhead pressing derivatives (WOPDs) and provides information regarding historical, technical, kinetic and kinematic mechanisms as well as potential benefits and guidelines to implement the use of WOPDs as training tools for sports populations. Only 13 articles were found in a search of electronic databases, which was employed to gather empirical evidence to provide an insight into the kinetic and kinematic mechanisms underpinning WOPDs. Practitioners may implement WOPDs such as push press, push jerk or split jerk from the back as well as the front rack position to provide an adequate stimulus to improve not only weightlifting performance but also sports performance as: (1) the use of WOPDs is an additional strategy to improve weightlifting performance; (2) WOPDs require the ability to develop high forces rapidly by an impulsive triple extension of the hips, knees and ankles, which is mechanically similar to many sporting tasks; (3) WOPDs may be beneficial for enhancing power development and maximal strength in the sport population; and, finally, (4) WOPDs may provide a variation in training stimulus for the sports population due to the technical demands, need for balance and coordination. The potential benefits highlighted in the literature provide a justification for the implementation of WOPDs in sports training. However, there is a lack of information regarding the longitudinal training effects that may result from implementing WOPDs.

Acute Effects of Resistance Exercise on Cognitive Function in Healthy Adults: A Systematic Review with Multilevel Meta-Analysis

### Background

Recent research has revealed a beneficial impact of chronic resistance exercise (RE) on brain function. However, it is unclear as to whether RE is also effective in an acute setting.

### Objective

To investigate the immediate effects of a single RE session on cognitive performance in healthy adults.

### Methods

A multilevel meta-analysis with random effects meta-regression model was used to pool the standardized mean differences (SMD) between RE and no-exercise (NEX) as well as between RE and aerobic exercise (AE). In addition to global cognitive function, effects on reported sub-domains (inhibitory control, cognitive flexibility, working memory, attention) were examined.

### Results

Twelve trials with fair methodological quality (PEDro scale) were identified. Compared to NEX, RE had a positive effect on global cognition (SMD: 0.56, 95% CI 0.22–0.90, p = 0.004), but was not superior to AE (SMD: − 0.10, 95% CI 0.01 to − 0.20, p = 0.06). Regarding cognitive sub-domains, RE, compared to NEX, improved inhibitory control (SMD: 0.73, 95% CI 0.21–1.26, p = 0.01) and cognitive flexibility (SMD: 0.36, 95% CI 0.17–0.55, p  = 0.004). In contrast, working memory (SMD: 0.35, 95% CI − 0.05 to 0.75, p  = 0.07) and attention (SMD: 0.79, 95% CI − 0.42 to 2.00, p = 0.16) remained unaffected. No significant differences in sub-domains were found between RE and AE (p > 0.05).

### Conclusion

RE appears to be an appropriate method to immediately enhance cognitive function in healthy adults. Further studies clearly elucidating the impact of effect modifiers such as age, training intensity, or training duration are warranted.

What is the Prevalence of Hip Intra-Articular Pathologies and Osteoarthritis in Active Athletes with Hip and Groin Pain Compared with Those Without? A Systematic Review and Meta-Analysis

### Background

In athletes, hip and groin pain is considered to be associated with hip intra-articular pathologies and hip osteoarthritis (OA). A greater understanding of the relationship between hip and groin pain and imaging findings is required.

### Objective

Our objective was to undertake a systematic review and meta-analysis to determine the prevalence of hip intra-articular pathologies and hip OA in athletes with and without hip and groin pain.

### Methods

Seven electronic databases were searched on 29 January 2018 for studies investigating the prevalence of hip intra-articular pathologies and hip OA using X-ray, magnetic resonance imaging, magnetic resonance arthrography or computed tomography. The search, study selection, quality appraisal and data extraction were performed by two independent reviewers. When studies were considered homogenous, meta-analysis was undertaken. A strength of evidence was given to pooled results.

### Results

Twenty studies reporting on the prevalence of hip intra-articular pathologies and hip OA in athletes were identified. Included studies were considered moderate to high risk of bias, with only three studies adjudged as low risk of bias. In asymptomatic athletes, limited evidence identified a labral tear prevalence of 54% per person and moderate evidence of 33% per hip. In symptomatic athletes, moderate evidence of a labral tear prevalence of 20% per hip was found. Moderate evidence of a cartilage defect prevalence of 10% per person was reported in asymptomatic athletes. In symptomatic athletes, cartilage defect prevalence was 7–40%. In asymptomatic athletes, the prevalence of hip OA was 0–17%, compared with 2% in symptomatic athletes.

### Conclusion

The prevalence of hip intra-articular pathologies and hip OA in symptomatic and asymptomatic athletes is variable. Labral tears and cartilage defects appear to be seen often in athletes with and without pain. Hip OA is rarely seen in athletes either with or without hip and groin pain.

### Study Registration

PROSPERO registration CRD42017082457.

Effect of Immobilisation on Neuromuscular Function In Vivo in Humans: A Systematic Review

### Background

Muscle strength loss following immobilisation has been predominantly attributed to rapid muscle atrophy. However, this cannot fully explain the magnitude of muscle strength loss, so changes in neuromuscular function (NMF) may be involved.

### Objectives

We systematically reviewed literature that quantified changes in muscle strength, size and NMF following periods of limb immobilisation in vivo in humans.

### Methods

Studies were identified following systematic searches, assessed for inclusion, data extracted and quality appraised by two reviewers. Data were tabulated and reported narratively.

### Results

Forty eligible studies were included, 22 immobilised lower and 18 immobilised upper limbs. Limb immobilisation ranged from 12 h to 56 days. Isometric muscle strength and muscle size declined following immobilisation; however, change magnitude was greater for strength than size. Evoked resting twitch force decreased for lower but increased for upper limbs. Rate of force development either remained unchanged or slowed for lower and typically slowed for upper limbs. Twitch relaxation rate slowed for both lower and upper limbs. Central motor drive typically decreased for both locations, while electromyography amplitude during maximum voluntary contractions decreased for the lower and presented mixed findings for the upper limbs. Trends imply faster rates of NMF loss relative to size earlier in immobilisation periods for all outcomes.

### Conclusions

Limb immobilisation results in non-uniform loss of isometric muscle strength, size and NMF over time. Different outcomes between upper and lower limbs could be attributed to higher degrees of central neural control of upper limb musculature. Future research should focus on muscle function losses and mechanisms following acute immobilisation.

### Registration

PROSPERO reference: CRD42016033692.

Maximal Sprint Speed and the Anaerobic Speed Reserve Domain: The Untapped Tools that Differentiate the World's Best Male 800 m Runners

### Abstract

Recent evidence indicates that the modern-day men's 800 m runner requires a speed capability beyond that of previous eras. In addition, the appreciation of different athlete subgroups (400–800, 800, 800–1500 m) implies a complex interplay between the mechanical (aerial or terrestrial) and physiological characteristics that enable success in any individual runner. Historically, coach education for middle-distance running often emphasises aerobic metabolic conditioning, while it relatively lacks consideration for an important neuromuscular and mechanical component. Consequently, many 800 m runners today may lack the mechanical competence needed to achieve the relaxed race pace speed required for success, resulting in limited ability to cope with surges, run faster first laps or close fast. Mechanical competence may refer to the skilled coordination of neuromuscular/mechanical (stride length/frequency/impulse) and metabolic components needed to sustain middle-distance race pace and adjust to surges efficiently. The anaerobic speed reserve (ASR) construct (difference between an athlete's velocity at maximal oxygen uptake [v $$\dot{V}$$ O2max]—the first speed at which maximal oxygen uptake [ $$\dot{V}$$ O2max] is attained) and their maximal sprint speed (MSS) offers a framework to assess a runner's speed range relative to modern-day race demands. While the smooth and relaxed technique observed in middle-distance runners is often considered causal to running economy measured during submaximal running, little empirical evidence supports such an assumption. Thus, a multidisciplinary approach is needed to examine the underpinning factors enabling elite 800 m running race pace efficiency. Here, we argue for the importance of utilising the ASR and MSS measurement to ensure middle-distance runners have the skills to compete in the race-defining surges of modern-day 800 m running.

Principles of Motor Learning to Support Neuroplasticity After ACL Injury: Implications for Optimizing Performance and Reducing Risk of Second ACL Injury

### Abstract

Athletes who wish to resume high-level activities after an injury to the anterior cruciate ligament (ACL) are often advised to undergo surgical reconstruction. Nevertheless, ACL reconstruction (ACLR) does not equate to normal function of the knee or reduced risk of subsequent injuries. In fact, recent evidence has shown that only around half of post-ACLR patients can expect to return to competitive level of sports. A rising concern is the high rate of second ACL injuries, particularly in young athletes, with up to 20% of those returning to sport in the first year from surgery experiencing a second ACL rupture. Aside from the increased risk of second injury, patients after ACLR have an increased risk of developing early onset of osteoarthritis. Given the recent findings, it is imperative that rehabilitation after ACLR is scrutinized so the second injury preventative strategies can be optimized. Unfortunately, current ACLR rehabilitation programs may not be optimally effective in addressing deficits related to the initial injury and the subsequent surgical intervention. Motor learning to (re-)acquire motor skills and neuroplastic capacities are not sufficiently incorporated during traditional rehabilitation, attesting to the high re-injury rates. The purpose of this article is to present novel clinically integrated motor learning principles to support neuroplasticity that can improve patient functional performance and reduce the risk of second ACL injury. The following key concepts to enhance rehabilitation and prepare the patient for re-integration to sports after an ACL injury that is as safe as possible are presented: (1) external focus of attention, (2) implicit learning, (3) differential learning, (4) self-controlled learning and contextual interference. The novel motor learning principles presented in this manuscript may optimize future rehabilitation programs to reduce second ACL injury risk and early development of osteoarthritis by targeting changes in neural networks.