Comparison of EMG activity in shank muscles between individuals with and without chronic ankle instability when running on a treadmill.

Changes in movement capabilities after an injury to the ankle may impose adaptations in the peripheral and central nervous system. The purpose of our study was to compare the electromyogram (EMG) profile of ankle stabilizer muscles and stride-time variation during treadmill running in individuals with and without chronic ankle instability (CAI). Recreationally active individuals with (n = 12) and without (n = 15) CAI ran on a treadmill at two speeds. EMG activity of four shank muscles as well as tibial acceleration data were recorded during the running trials. EMG amplitude, timing of EMG peaks, and variation in stride-time were analyzed from 30 consecutive stride cycles. EMG data were time-normalized to stride duration and amplitude was normalized relative to the appropriate maximal voluntary contraction (MVC) task. Individuals with CAI had similar EMG amplitudes and peak timing, but an altered order of peak EMG activity in ankle stabilizer muscles, a significantly greater EMG amplitude for PL with an increase in speed, and a greater stride-time variability during treadmill running compared with individuals who had no history of ankle sprains. The results of our study indicate that individuals with CAI exhibit altered activation strategies for ankle stabilizer muscles when running on a treadmill.

Foam rolling during a simulated half-time attenuates subsequent soccer-specific performance decrements.

The passive nature of the half-time period with soccer/football can result in second-half performance decrements. As foam rolling (FR) can increase range of motion, neuromuscular efficiency, and enhance arterial function, the inclusion of FR during half-time may attenuate performance decrements. The objective of this acute study was to compare FR versus passive recovery during a simulated half-time period on simulated second-half soccer pass, sprint performance as well as quality of recovery. Thirteen male soccer players simulated a soccer match by performing two bouts of 15 × 20 m sprints with 30-s rest intervals. The bouts were separated by 10-min with either a passive recovery or they performed five FR exercises on both legs for 45-s each with 15-s rest. Tests were conducted before and following the simulated half-time period and consisted of Total Quality of Recovery (TQR), Loughborough Soccer Pass Test (LSPT), blood lactate (LAC), and sprint velocity of the simulated soccer match. Heart rates (HR) were recorded at the end of each test session and each sprint. Results showed no significant changes between conditions for TQR, LSPT, LAC and HR. However, while all sprint speed measures (mean, best of 15 sprints and mean of the first 5 sprints) significantly decreased with the passive condition, no decrement was noted with all sprint measures with the FR condition; there was only a significant (p = 0.001; d = 0.63) 2.1% decrease with the mean of the first 5 sprints. In conclusion, there is some evidence that FR may be beneficial to attenuate sprint speed impairments.

The effect of carbohydrate and caffeine mouth rinsing on kicking performance in competitive Taekwondo athletes during Ramadan.

Mouth rinsing has been proposed as a strategy to minimize performance decrements during Ramadan. We investigated the effect of 4 weeks of Ramadan on kicking performance in 27 Taekwondo athletes performing weekly Taekwondo Anaerobic Intermittent Kick Tests (TAIKT). The effects of a placebo, 6.4% glucose and 6-mg/kg caffeine mouth rinses on TAIKT performance and perceived exertion were investigated before, during weekly training sessions, and after Ramadan in a counterbalanced, crossover design. Ramadan had a significant negative impact on the percentage of successful kicks in Week 1 of Ramadan (pre: 76.7±0.4%, Week 1: 69.9±3.2%). The percentage of successful kicks was significantly greater in the caffeine mouth rinse condition compared to the glucose and placebo conditions during the first 3 weeks of Ramadan (caffeine: 38.3±6.8%, glucose: 36.4±6.9%, placebo: 36.0±6.5%). Caffeine decreased perceived exertion during Ramadan (0.74-1.15 AU, p>0.05). Our results showed that Ramadan had a significant negative effect on repeated high-intensity kicking efforts that should be considered when training and competing. Additionally, there were significant positive effects of a caffeine mouth rinse in a sport-specific test. These data suggest that athletes can consider mouth rinsing as a strategy to enhance performance when undertaking training or competition during a period of privation.

Stance foot alignment and hand positioning alter star excursion balance test scores in those with chronic ankle instability: What are we really assessing?

OBJECTIVE: The literature has consistently shown that the Star Excursion Balance Test (SEBT) is a reliable and valid tool to anticipate the risk of lower extremity injury, assess dynamic postural control differences among groups, and assess the effectiveness of balance training programs in both healthy individuals and people with lower extremity injuries. However, there is no standard administration technique for the SEBT in research, clinical practice, or performance settings. Therefore, the purpose of this investigation was to compare six different combinations (3 different foot alignments × 2 hand positions) on the SEBT performance in those with chronic ankle instability (CAI). DESIGN: Repeated Measures Design. SETTING: University Research Laboratory. PARTICIPANTS: Twenty-five university students with CAI (12 males, 13 females; age: 20.3 ± 2.4 years, height: 172.7 ± 7.4 cm, weight: 77.5 ± 15.3 kg. , BMI: 25.9 ± 4.0 kg/m2) voluntarily participated in the study. METHODS: Six different SEBT positions were used to assess dynamic postural control. Three foot positions: 1) Foot centered; 2) Toe fixed; and 3) Toe-heel changing and two hand placements: 1) Hands free and 2) Hands on the hips were used in this study. After 6familiarization trials for each condition, three Star Excursion Balance Test scores were recorded. MAIN OUTCOME MEASURES: Normalized reach distance (% of leg length) in the anterior, posteromedial, and posterolateral directions as well as a composite reach score quantified dynamic postural control. RESULTS: Both foot alignment and hand position significantly altered normalized SEBT reach distance in the anterior (p < 0.003), posteromedial (p < 0.001), posterolateral (p < 0.001), and composite reach scores (p < 0.001). CONCLUSION: Different foot alignments and hand constraints significantly altered normalized reach distances and the composite score in individuals with CAI. These results do not suggest that any combination of foot alignments and/or hand constraints is superior. However, changing the toe/heel position, while maintaining hands on the hips, may provide the best standardization for clinicians and researchers.

Comparative Effects of Different Balance-Training-Progression Styles on Postural Control and Ankle Force Production: A Randomized Controlled Trial.

CONTEXT: Despite the effectiveness of balance training, the exact parameters needed to maximize the benefits of such programs remain unknown. One such factor is how individuals should progress to higher levels of task difficulty within a balance-training program. Yet no investigators have directly compared different balance-training-progression styles. OBJECTIVE: To compare an error-based progression (ie, advance when proficient at a task) with a repetition-based progression (ie, advance after a set amount of repetitions) style during a balance-training program in healthy individuals. DESIGN: Randomized controlled trial. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 28 (16 women, 12 men) physically healthy young adults (age = 21.57 ± 3.95 years, height = 171.60 ± 11.03 cm, weight = 72.96 ± 16.18 kg, body mass index = 24.53 ± 3.7). INTERVENTION(S): All participants completed 12 supervised balance-training sessions over 4 weeks. Each session consisted of a combination of dynamic unstable-surface tasks that incorporated a BOSU ball and lasted about 30 minutes. MAIN OUTCOME MEASURE(S): Static balance from an instrumented force plate, dynamic balance as measured via the Star Excursion Balance Test, and ankle force production in all 4 cardinal planes of motion as measured with a handheld dynamometer before and after the intervention. RESULTS: Selected static postural-control outcomes, dynamic postural control, and ankle force production in all planes of motion improved (P < .05). However, no differences between the progression styles were observed (P > .05) for any of the outcome measures. CONCLUSIONS: A 4-week balance-training program consisting of dynamic unstable-surface exercises on a BOSU ball improved dynamic postural control and ankle force production in healthy young adults. These results suggest that an error-based balance-training program is comparable with but not superior to a repetition-based balance-training program in improving postural control and ankle force production in healthy young adults.

The Effects of Sex, Limb Dominance, and Soccer Participation on Knee Proprioception and Dynamic Postural Control.

CONTEXT: Both female athletes' participation in soccer and associated injuries have greatly increased in recent years. One issue is the 2-9 times greater incidence of noncontact anterior cruciate ligament (ACL) injuries in female athletes relative to male athletes in comparable sports. Several factors such as limb dominance and sporting history have been proposed to play a role in ACL incidence rates between male and female athletes. However, evidence about the effects of these factors and how they interact with sex is mixed, and thus no consensus exists. OBJECTIVE: To quantify the effects of sports participation, limb dominance, and sex on dynamic postural control and knee-joint proprioception. DESIGN: Cross-sectional study. SETTING: University research laboratory. PARTICIPANTS: 19 male soccer players, 17 female soccer players, 19 sedentary men, and 18 sedentary women. INTERVENTION: Joint-position sense was tested using reproduction of passive positioning on a Biodex isokinetic dynamometer (30°, 45°, and 60° from 90° of knee flexion). Three Star Excursion Balance Test directions were used to assess dynamic postural control. MAIN OUTCOME MEASURE: Normalized reach distance (% of leg length) in the anterior, posteromedial, and posterolateral directions on each leg quantified dynamic postural control. Average absolute error and constant error for both limbs quantified joint-position sense. RESULTS: Posteromedial reach distance was significantly better in soccer players than sedentary individuals (P = .006). Anterior reach distance was significantly better (P = .04) in sedentary individuals than soccer players. No limb-dominance or sex differences were identified for dynamic postural control, and no differences in absolute- or constant-error scores were identified. CONCLUSION: Sporting history has a direction-specific impact on dynamic postural control. Sporting history, sex, and limb dominance do not influence knee-joint proprioception when tested in an open kinetic chain using passive repositioning.

Learning effects associated with the least stable level of the biodex® stability system during dual and single limb stance.

The Biodex® Stability System (BSS) has high test-retest reliability when stable (high) resistance levels are used. However, reliability data for lower stability levels, associated with more pronounced learning curves, are rare in the existing literature. Thus, it is likely that BSS scores obtained from lower stability levels require greater familiarization (i.e. practice) to achieve a stable score both within and between test sessions. Therefore, the purpose of this investigation was to determine if a commonly reported 6 trial sequence (3 practice trials, 3 test trials) used with the BSS can achieve a stable within session score on the lowest stability level (i.e. level 1). The secondary purpose was to evaluate the test-retest reliability of the lowest BSS resistance level over a 10-week period. Twenty sedentary university students (11 male, 9 female; age: 21.5 ± 1.9 years, height: 1.7 ± 0.1 m, weight: 66.3 ± 12.1 kg, BMI: 22.4 ± 2.3) voluntarily participated. Participants completed two test sessions separated by 10-weeks. Twelve, 20-second trials (six dual limb stance, six single limb stance on the dominant limb) on the lowest stability level were completed during both test sessions by all participants. A stable within session dual and single limb stance score was achieved with a maximum of 3 familiarization trials. Reliability ranged between poor and good across all outcomes but all outcomes had large minimal detectable change scores. At least 3 stance specific familiarization trials are needed to achieve a stable BSS score within a single test session on the lowest resistance level. However, the inconsistent reliability and high minimal detectable changes scores suggest that the lowest resistance level should not be used as an objective marker of rehabilitation progress over extended periods of time (e.g. 10-weeks). Key pointsLevel 1 BSS scores should not be used as a test setting to assess rehabilitation.Familiarization trials should not be underestimated by researchers/clinicans.Lower stability levels on the BSS may not be appropriate for use as an objective marker of progression due to poor reliability of the scores over time.

Relationship between anthropometric factors, gender, and balance under unstable conditions in young adults.

The objective of this study was to evaluate the relationship between the anthropometric factors of height, body mass, body mass index and postural balance and to compare the balance indices between genders in the upright standing position, in healthy adult subjects under conditions of instability. Forty individuals were subjected to functional tests of body stability using the Biodex Balance System, and the resulting indices were correlated with body mass, height, and body mass index, and also compared between genders. Body mass was the main anthropometric factor that influenced variations in postural balance, with a high correlation between groups and with all variables. A linear regression analysis showed that body mass associated with BMI explained 66% of the overall stability, and body mass explained 59% of the anteroposterior stability index and 65% of the mediolateral stability index. In the female group, body mass explained 72% of the overall balance, 66% of the anteroposterior, and 76% of the medio-lateral stability index. Increased body mass requires greater movements to maintain postural balance. Height and BMI presented moderate correlations with balance. Women showed less movement than men on the Biodex Balance System.

The effect of instability training on knee joint proprioception and core strength.

Although there are many studies demonstrating increased trunk activation under unstable conditions, it is not known whether this increased activation would translate into meaningful trunk strength with a prolonged training program. Additionally, while balance-training programs have been shown to improve stability, their effect on specific joint proprioception is not clear. Thus the objective of this study was to examine training adaptations associated with a 10-week instability-training program. Participants were tested pre- and post-training for trunk extension and flexion strength and knee proprioception. Forty-three participants participated in either a 10-week (3 days per week) instability-training program using Swiss balls and body weight as resistance or a control group (n = 17). The trained group increased (p < 0. 05) trunk extension peak torque/body weight (23.6%) and total work output (20.1%) from pre- to post-training while the control group decreased by 6.8% and 6.7% respectively. The exercise group increased their trunk flexion peak torque/body weight ratios by 18.1% while the control group decreased by 0.4%. Knee proprioception (combined right and left joint repositioning) improved 44.7% from pre- to post-training (p = 0.0006) and persisted (21.5%) for 9 months post-training. In addition there was a side interaction with the position sense of the right knee at 9 months showing 32.1% (p = 0.03) less deviation from the reference angle than the right knee during pre-testing. An instability-training program using Swiss balls with body weight as resistance can provide prolonged improvements in joint proprioception and core strength in previously untrained individuals performing this novel training stress which would contribute to general health. Key pointsAlthough traditional free weight resistance exercises have been recommended as most beneficial for improving strength and power in athletes (Behm et al., 2010b), an IT program using Swiss balls and body weight as a resistance may provide an alternative starting point for the sedentary untrained population.As it is well documented that force or strength is decreased when unbalanced (Behm et al., 2010b) and balance-training programs improve balance (Behm and Kean 2006), this type of instability RT program can provide significant adaptations to improve trunk strength especially with the untrained.This type of training should also be incorporated into a new program as the improvements in joint proprioception may help protect from joint injuries over a protracted period.The finding that improved joint proprioception persists for months after training should be emphasized to those individuals whose training is regularly or inconsistently interrupted.

Effects of Swiss-ball core strength training on strength, endurance, flexibility, and balance in sedentary women.

The purpose of this study was to investigate the effects of Swiss-ball core strength training on trunk extensor (abdominal)/flexor (lower back) and lower limb extensor (quadriceps)/flexor (hamstring) muscular strength, abdominal, lower back and leg endurance, flexibility and dynamic balance in sedentary women (n = 21; age = 34 ± 8.09; height = 1.63 ± 6.91 cm; weight = 64 ± 8.69 kg) trained for 45 minutes, 3 d·wk-1 for 12 weeks. Results of multivariate analysis revealed significant difference (p ≤ 0.05) between pre and postmeasures of 60 and 90° s trunk flexion/extension, 60 and 240° s-1 lower limb flexion/extension (Biodex Isokinetic Dynamometer), abdominal endurance (curl-up test), lower back muscular endurance (modified Sorensen test), lower limb endurance (repetitive squat test), lower back flexibility (sit and reach test), and dynamic balance (functional reach test). The results support the fact that Swiss-ball core strength training exercises can be used to provide improvement in the aforementioned measures in sedentary women. In conclusion, this study provides practical implications for sedentary individuals, physiotherapists, strength and conditioning specialists who can benefit from core strength training with Swiss balls.