Sport Specialization's Impact on Female Adolescent Athletes' Lower-Extremity Neuromuscular Control: A Critically Appraised Topic

CLINICAL SCENARIO

Nearly 60 million youth ages 6-18 participate in athletics within the United States. Over the last 30 years, the outlook on youth sport participation has drastically changed, resulting in an increased emphasis on performance and college sport participation. These evolving expectations have created a sense of perfectionism, demanding more time and energy to be placed into a single sport, resulting in an increased prevalence of sport specialization, and consequently, an increased rate of injury.

CLINICAL QUESTION

What is the impact of sport specialization on lower-extremity neuromuscular control in female adolescent athletes?

SUMMARY OF KEY FINDINGS

Four studies were included, all comparing movement efficiency and movement patterns among multisport and sport-specialized female adolescent athletes. Three studies showed that sport specialization is associated with lower-extremity biomechanical alterations that are indicative of altered levels of neuromuscular control, which can predispose an individual to an increased risk of injury. One study concluded that no differences in neuromuscular control exist when comparing sport-specialized to multisport adolescent female athletes.

CLINICAL BOTTOM LINE

Sport specialization has the potential to create negative alterations in a female adolescent athletes' lower-extremity biomechanics, leading to the creation of altered levels of neuromuscular control and a possible increased risk for injury.

STRENGTH OF RECOMMENDATION

Level B evidence exists to support the conclusion that sport specialization negatively affects a female adolescent athlete's lower-extremity neuromuscular control.

A novel guideline for the analysis of linear acceleration mechanics - outlining a conceptual framework of 'shin roll' motion

Linear acceleration is a key performance determinant and major training component of many sports. Although extensive research about lower limb kinetics and kinematics is available, consistent definitions of distinctive key body positions, the underlying mechanisms and their related movement strategies are lacking. The aim of this 'Method and Theoretical Perspective' article is to introduce a conceptual framework which classifies the sagittal plane 'shin roll' motion during accelerated sprinting. By emphasising the importance of the shin segment's orientation in space, four distinctive key positions are presented ('shin block', 'touchdown', 'heel lock' and 'propulsion pose'), which are linked by a progressive 'shin roll' motion during swing-stance transition. The shin's downward tilt is driven by three different movement strategies ('shin alignment', 'horizontal ankle rocker' and 'shin drop'). The tilt's optimal amount and timing will contribute to a mechanically efficient acceleration via timely staggered proximal-to-distal power output. Empirical data obtained from athletes of different performance levels and sporting backgrounds are required to verify the feasibility of this concept. The framework presented here should facilitate future biomechanical analyses and may enable coaches and practitioners to develop specific training programs and feedback strategies to provide athletes with a more efficient acceleration technique.

Relationships between balance and physical fitness variables in firefighter recruits

BACKGROUND

Research has suggested that balance ability contributes to musculoskeletal injury (MSKI) rates in firefighters. Though the Y-Balance Test (YBT) can predict injury, it is unclear what physical measures inform YBT performance in firefighters. Thus, there is a lack of knowledge regarding best practice for improving balance in firefighters.

OBJECTIVE

To evaluate the relationship between the YBT and fitness measures, including body composition, aerobic capacity, functional total-body power, upper and lower-body strength, and movement efficiency, among firefighters.

METHODS

Dynamic balance (YBT), body mass index (BMI), body-fat percentage (BF%), fat free mass (FFM), aerobic capacity (VO2max), stair climb (SC), upper (1RMbench) and lower-body (1RMsquat) strength, and Fusionetics™ Movement Efficiency Screen (ME) measures were collected among 35 firefighter recruits. Pearson correlation coefficients were used to examine relationships between YBT and the performance measures.

RESULTS

Dynamic balance ability in firefighter recruits is significantly (p < 0.05) related to BMI, lower-body strength, and movement quality, but not with aerobic capacity, stair climb performance, and upper body strength.

CONCLUSIONS

Greater YBT performance in firefighter recruits is associated with lower BMI, greater functional movement, and greater lower-body strength. Future research is warranted to incorporate these elements into balance training programs for firefighter recruits.

Measurement of the time required for termites to pass each other in tunnels of different curvatures

Subterranean termites construct complex tunnel networks for foraging. During travel in the tunnels, termites often encounter one another when passing in opposite directions. Such encounters are likely to affect the "movement efficiency," which is the time required for a termite to travel a certain distance in a tunnel. In this study, we explored how individual-individual encounters affect movement efficiency in tunnels by measuring the time (τ) taken by two termites to pass one another in tunnels of different curvatures. Artificial tunnels of 5 cm in length and variable widths (W) of 2, 3, or 4 mm were made. Tunnel distance (D) was 2, 3, 4, or 5 cm. When D had a higher value, curvature was lower. When W = 2, τ was significantly shorter in the tunnel with D = 5 than in tunnels of D = 2, 3, or 4, whereas τ was statistically the same for D = 2, 3 and 4. When W = 3, τ was shorter in the tunnel with D = 5 than for D = 3 and 4, while τ was longer in the tunnel with D = 2 than for D = 3 and 4. When W = 4, τ was longer in the tunnels with D = 2 and 3 than for D = 4 and 5. Based on these observations, 3 types of termite behavior were identified: biased walking, backward walking, and zigzag walking. We considered these results in relation to foraging efficiency.

Attentional focusing instructions and force production

Research progress assessing the role of attentional focusing instructions on skill acquisition and performance has lead researchers to apply this approach to force production tasks. Initial converging evidence indicates that force production tasks are sensitive to verbal instruction; externally focused instructions (onto movement outcomes, or onto the object force is being exerted against) are shown to be more beneficial than internally focused instructions (focusing attention onto the movements being executed). These benefits are observed for maximal and accurate force production, as well as the maintenance of force production in prolonged tasks. A range of mechanisms are identified supporting the proposal that an external focus promotes movement efficiency in line with energy and effort conservation. Future research is required to assess how this developing body of work interacts with the broader understanding of psychological and physiological factors implicated in the effective production, maintenance, and limitation of maximal or sub-maximal forces.