Ankle bracing's effects during a modified agility task: analysis of sEMG, impulse, and time to complete using a crossover, repeated measures design.

This study explored the effects of no braces, softshell (AE), and semi-rigid (T1) ankle braces on time to complete a modified agility task, as well as lower extremity muscle activity and impulse during the change of direction component of the task. Thirty-nine healthy, active individuals completed a modified agility task under the three brace conditions. Time to complete the modified agility task, along with mean surface electromyographic activity (sEMG) and impulse during the deceleration and propulsive phases of the task were measured. There were no significant differences across conditions with respect to sEMG or impulse measures during the deceleration or propulsive phases. There was a significant change in time to complete the modified agility task, F(2,76) = 17.242, p< 0.001, ηp2 = 0.312. Post-hoc analysis revealed a significant increase in time to complete the modified agility task when wearing the AE (0.16 (95% CI, 0.062 to 0.265) seconds, p< 0.001) and T1 (0.20 (95% CI, 0.113 to 0.286) seconds, p< 0.001) ankle braces compared to no braces. It appears that performance on a modified agility task may be diminished when wearing ankle braces, although sEMG activity and impulse are unaffected.

Effect of Neck Strength on Simulated Head Impacts During Falls in Female Ice Hockey Players.

This study examined the effect of isometric cervical strength and impact location of the hockey helmet in mitigating the risk of concussions for two different mechanisms of injury from a fall during head impact simulation testing. Isometric cervical strength was measured on 25 female hockey players to compute and model neck strength on a mechanical neckform. A dual-rail vertical drop system with a helmet mounted on a surrogate headform simulated the mechanisms of injury causing concussions on female ice hockey players. Measures of peak linear acceleration and risk of injury due to a head collision (GSI) were used to assess the magnitude of the head impact due to a fall across three neck strength measures (weak, average, strong), three helmet locations (front, rear, side), and two mechanisms of injury (direct, whiplash+impact). A three-way ANOVA revealed a significant main effect for impact mechanism on the magnitude of peak linear acceleration and GSI, with the whiplash+impact mechanism generating significantly greater peak linear acceleration and GSI than the direct impact mechanism. A significant two-way interaction effect was found between impact location and mechanism of injury on peak linear acceleration measures, with the direct impact on the side location generating significantly greater peak linear acceleration than the frontal location. On the contrary, the whiplash+impact mechanism revealed that the frontal impact location produced significantly greater peak linear acceleration than the side location. This outcome suggests the geometry of the helmet material and the type of mechanism of injury both play a role in concussion risk.

Ankle bracing's effects on lower extremity iEMG activity, force production, and jump height during a Vertical Jump Test: An exploratory study.

OBJECTIVE: To determine if softshell (AE) and semi-rigid (T1) ankle braces affect lower extremity iEMG activity, force, and jump height during a Vertical Jump Test. DESIGN: Repeated measures, crossover. SETTING: Laboratory. PARTICIPANTS: 42 healthy, active individuals. OUTCOME MEASURES: Vertical jump height, iEMG activity, peak vGRF. RESULTS: There was significant change across conditions in lateral gastrocnemius (LG) iEMG activity, F(2,70) = 5.31, p = .007, ηp2 = 0.132, with T1 LG iEMG being significantly less (-2.08(99% CI, -3.98 to 0.18) %MVIC, p = .004) than no brace. Significant changes were seen in rectus femoris (RF) iEMG activity, F(2,68) = 6.36, p = .003, ηp2 = 0.158, with T1 RF iEMG activity being significantly less than AE RF iEMG activity (-2.78(99% CI, -5.36 to -0.19) %MVIC, p = .005). There was a significant change in vertical jump height across conditions, F(2,78) = 22.13, p < .0005, ηp2 = 0.362, with a significant decrease in the AE (-2.41(99% CI, -3.66 to -1.17) cm, p < .0005) and T1 conditions (-2.89(99% CI,-4.56 to -1.23) cm, p < .0005), compared to no brace. CONCLUSION: Vertical jump height is significantly reduced when wearing ankle braces. Effects on lower extremity iEMG activity are dependent upon brace type.

The Effects of Ankle Braces on Lower Extremity Electromyography and Performance During Vertical Jumping: A Pilot Study.

Ankle braces have been hypothesized to prevent ankle injuries by restricting range of motion (ROM) and improving proprioception at the ankle. As such, ankle braces are commonly worn by physically active individuals to prevent ankle injuries. Despite their widespread use, the effects that ankle braces have on athletic performance measures, such as vertical jumping, remains unclear. Furthermore, although ankle braces are known to restrict normal ROM at the ankle, little is known about the effects that ankle braces have on the lower extremity proximal to the ankle, specifically muscular activation. Therefore, the purpose of this pilot study was to determine if lower extremity surface electromyographic activity (sEMG) and performance was affected in 5 males and 5 females by wearing softshell (AE) and semi-rigid (T1) ankle braces during a Vertical Jump Test, and to establish a basis for future investigation. Vertical jump height was not significantly affected (p > .05) in the AE (37.49 ± 11.61 cm) and T1 (36.3 ± 11.77 cm) ankle brace conditions, relative to the no brace (38.17 ± 12.01 cm) condition. No significant differences in sEMG of the lateral gastrocnemius and biceps femoris were present across conditions. There was a tendency for sEMG of the rectus femoris to decrease when wearing AE (195.71 ± 100.43 %MVC) and T1 (183.308 ± 92.73 %MVC) braces, compared to no braces (210.08 ± 127.46 %MVC), and warrants further investigation using a larger sample. Until more research is conducted, however, clinicians should not be concerned about ankle braces significantly affecting proximal muscle activation during vertical jumping.

The effect of patellar taping on lower extremity running kinematics in individuals with patellofemoral pain syndrome.

Purpose: To investigate the effects of patellar taping (Leukotape® (LT), Pinetown, South Africa, Kinesio Tape (KT), Dortmund, Germany, or no tape) on lower extremity kinematics in runners with and without patellofemoral pain syndrome (PFPS). Methods: In total, 20 healthy individuals and 12 with PFPS ran on a treadmill under different taping conditions and lower extremity kinematics and stride characteristics were obtained using Peak Motus Software, Colorado, USA. Data were analyzed using descriptive statistics and mixed factorial analysis of variance (p < 0.05). Results: Significant taping effects were found for hip (F(2,60) = 16.79, p = 0.0001) and knee (F(2,60) = 17.27, p = 0.0001) flexion angles at initial contact, and peak hip flexion angles during swing (F(2,60) = 6.55, p = 0.003). Increased flexion was noted with LT more than KT and no tape conditions. Similarly, peak knee flexion angles during stance (F(2,60) = 3.51, p = 0.03) and flight time (F(2,60) = 5.01, p = 0.01) revealed significant taping effects, with LT resulting in more flexion (p = 0.04) and shorter flight times (p = 0.01) than the no tape condition. Furthermore, a significant taping effect was seen for peak knee flexion angle during swing (F(2,60) = 4.96, p = 0.01), with the KT resulting in less flexion than LT (p = 0.04) and no tape conditions (p = 0.04). Conclusion: The application of tape during running may impact on hip and knee flexion angles at initial contact, as well as flight time.

Anthropometric and physical abilities profiles: US National Skeleton Team.

The aim of this study was to characterize sprint ability, anthropometry, and lower extremity power in the US National Team Skeleton athletes. Fourteen athletes (male n = 7; mean +/- SD: height 1.794 +/- 0.063 m, body mass 81.2 +/- 3.7 kg, age 26.9 +/- 4.1 years; female n = 7; 1.642 +/- 0.055 m, 60.1 +/- 5.9 kg, 27.3 +/- 6.9 years) volunteered to participate. Sprinting ability was measured over multiple intervals using custom infrared timing gates in both an upright and a crouched sprint. The crouched sprint was performed while pushing a wheeled-simulated skeleton sled on rails on an outdoor skeleton and bobsleigh start track. Crouched skeleton sprint starts were able to achieve about 70% to 85% of the upright sprint times. The mean somatotype ratings for females were: 3.5-3.5-2.1, and males: 3.6-4.9-1.9. Lower extremity strength and power were measured via vertical jumps on a portable force platform using squat and countermovement jumps, and jumps with added mass. Jump height, power, rate offorce development and peak force were determined from force-time data. Lower extremity strength and power were strongly correlated with both upright and crouched sprint times. The results indicated that these athletes are strong sprinters with varying body structures, mostly mesomorphic, and that stronger and more powerful athletes tend to be better starters.

A kinematic analysis of high-speed treadmill sprinting over a range of velocities.

INTRODUCTION: The purpose of this study was to measure changes in stride characteristics and lower-extremity kinematics of the hip and knee as a function of increasing treadmill velocity, at velocities ranging from submaximal to near maximal. METHODS: Six power/speed athletes experienced at sprinting on a treadmill performed trials at 70%, 80%, 90%, and 95% of their previous individual maximum velocity, with video data collected in the sagittal view at 60 Hz. RESULTS: Significant differences were seen in stride frequency (70%, 80%, P < 0.01; 90%, P < 0.05), stance time (70%, 80%, P < 0.01; 90%, P < 0.05) flight time (70%, P < 0.01; 80%, P < 0.05), hip flexion angle (70%, P < 0.01), hip flexion angular velocity (70%, P < 0.01), hip extension angular velocity (70%, 80%, P < 0.01), knee flexion angular velocity (70%, 80%, P < 0.01), and knee extension angular velocity (70%, P < 0.01), as compared with the near maximum (95%) velocity. Coefficient of variation (CV) values showed that the positional variables at the hip and knee were more variable at faster test conditions, indicating that kinematic changes occur as a function of increased treadmill velocity. CONCLUSIONS: The results indicated that at slower velocities, there were differences in the stride characteristics and lower-extremity kinematics while sprinting on a treadmill. As the velocity approached near maximum mechanical breakdown was seen, suggesting that velocities greater than 90% should be used selectively during treadmill training.