Hip thrust and back squat training elicit similar gluteus muscle hypertrophy and transfer similarly to the deadlift.

We examined how set-volume equated resistance training using either the back squat (SQ) or hip thrust (HT) affected hypertrophy and various strength outcomes. Untrained college-aged participants were randomized into HT (n = 18) or SQ (n = 16) groups. Surface electromyograms (sEMG) from the right gluteus maximus and medius muscles were obtained during the first training session. Participants completed 9 weeks of supervised training (15-17 sessions), before and after which gluteus and leg muscle cross-sectional area (mCSA) was assessed via magnetic resonance imaging. Strength was also assessed prior to and after the training intervention via three-repetition maximum (3RM) testing and an isometric wall push test. Gluteus mCSA increases were similar across both groups. Specifically, estimates [(-) favors HT (+) favors SQ] modestly favored the HT versus SQ for lower [effect ±SE, -1.6 ± 2.1 cm2; CI95% (-6.1, 2.0)], mid [-0.5 ± 1.7 cm2; CI95% (-4.0, 2.6)], and upper [-0.5 ± 2.6 cm2; CI95% (-5.8, 4.1)] gluteal mCSAs but with appreciable variance. Gluteus medius + minimus [-1.8 ± 1.5 cm2; CI95% (-4.6, 1.4)] and hamstrings [0.1 ± 0.6 cm2; CI95% (-0.9, 1.4)] mCSA demonstrated little to no growth with small differences between groups. mCSA changes were greater in SQ for the quadriceps [3.6 ± 1.5 cm2; CI95% (0.7, 6.4)] and adductors [2.5 ± 0.7 cm2; CI95% (1.2, 3.9)]. Squat 3RM increases favored SQ [14 ± 2 kg; CI95% (9, 18),] and hip thrust 3RM favored HT [-26 ± 5 kg; CI95% (-34, -16)]. 3RM deadlift [0 ± 2 kg; CI95% (-4, 3)] and wall push strength [-7 ± 12N; CI95% (-32, 17)] similarly improved. All measured gluteal sites showed greater mean sEMG amplitudes during the first bout hip thrust versus squat set, but this did not consistently predict gluteal hypertrophy outcomes. Squat and hip thrust training elicited similar gluteal hypertrophy, greater thigh hypertrophy in SQ, strength increases that favored exercise allocation, and similar deadlift and wall push strength increases.

Hip thrust and back squat training elicit similar gluteus muscle hypertrophy and transfer similarly to the deadlift.

Purpose: We examined how set-volume equated resistance training using either the back squat (SQ) or hip thrust (HT) affected hypertrophy and various strength outcomes. Methods: Untrained college-aged participants were randomized into HT or SQ groups. Surface electromyograms (sEMG) from the right gluteus maximus and medius muscles were obtained during the first training session. Participants completed nine weeks of supervised training (15-17 sessions), before and after which we assessed muscle cross-sectional area (mCSA) via magnetic resonance imaging and strength via three-repetition maximum (3RM) testing and an isometric wall push test. Results: Glutei mCSA growth was similar across both groups. Estimates [(-) favors HT; (+) favors SQ] modestly favored the HT compared to SQ for lower [effect ± SE, -1.6 ± 2.1 cm2], mid [-0.5± 1.7 cm2], and upper [-0.5 ± 2.6 cm2], but with appreciable variance. Gluteus medius+minimus [-1.8 ± 1.5 cm2] and hamstrings [0.1 ± 0.6 cm2] mCSA demonstrated little to no growth with small differences between groups. Thigh mCSA changes were greater in SQ for the quadriceps [3.6 ± 1.5 cm2] and adductors [2.5 ± 0.7 cm2]. Squat 3RM increases favored SQ [14 ± 2.5 kg] and hip thrust 3RM favored HT [-26 ± 5 kg]. 3RM deadlift [0 ± 2 kg] and wall push strength [-7 ± 13 N] similarly improved. All measured gluteal sites showed greater mean sEMG amplitudes during the first bout hip thrust versus squat set, but this did not consistently predict gluteal hypertrophy outcomes. Conclusion: Nine weeks of squat versus hip thrust training elicited similar gluteal hypertrophy, greater thigh hypertrophy in SQ, strength increases that favored exercise allocation, and similar strength transfers to the deadlift and wall push.

Impact of Two Types of Fitness Programs on Soldier Physical Fitness.

This study compared an expert supervised, fully resourced physical training (PT) program compared to a traditional physical training PT plan on Army Officer Candidate School (OSC) soldier fitness outcomes. This retrospective cohort study compared 228 OCS soldiers (179 male [26.74±3.78 years] and 49 female [26.55±4.18 years]) in two companies for 12 weeks. One company participated in a fully resourced PT program designed by fitness experts to improve overall fitness and mobility (TAP-C). One company participated in traditional physical training designed to excel on the Army combat fitness test (ACFT, includes deadlift, power throw, push up, sprint-drag-carry, core strength, run) developed and led by OCS soldiers with standard resources. We assessed performance on the ACFT events, and grip strength, standing broad jump, overhead squat, and 90/90 switch assessment. Analysis of covariance was used to compare main effects of company on ACFT measures, controlling for covariates of pretest score differences and sex. Results included a significant effect of group on ACFT performance (N=228), F(1, 223) = 12.8, p<0.001 and on performance of five of the six ACFT events: MDL, F(1, 223) = 5.44, p = 0.021; HRP, F(1, 223) = 11.67, p < 0.001; SDC, F(1, 223) = 20.06, p < 0.001; LTK, F(1, 223) = 16.95, p < 0.001; and 2MR, F(1, 223) = 23.76, p < 0.001. The traditional company performed significantly better on ACFT muscular, anerobic and aerobic endurance focused events; the TAP-C company performed significantly better on muscular strength/explosive power events and mobility assessments.

Lower-Extremity Motor Synergies in Individuals With and Without Chronic Ankle Instability.

Current theoretical models suggest that ankle sprain copers exhibit movement adaptations contributing to the avoidance of chronic ankle instability. However, few studies have examined adaptations at the level of biomechanical motor synergies. The purpose was to examine characteristics of the support moment synergy between individuals with chronic ankle instability, copers, and healthy individuals. A total of 48 individuals participated in the study. Lower-extremity kinetics and variability in the moment of force patterns were assessed during the stance phase of walking trials. The copers exhibited reductions in the support moment during the load response and preswing phase compared with the chronic ankle instability group, as well as during the terminal stance and preswing phase compared the healthy group. The copers also exhibited reductions in the hip extensor moment and ankle plantarflexion moment compared with healthy and chronic ankle instability groups during intervals of stance phase. Variability of the support moment and knee moment was greater in the copers compared with the chronic ankle instability group. Dampening of the support moment and select joint moments exhibited by the copers may indicate an adaptive mechanism to mitigate loading perturbations on the previously injured ankle. Heightened motor variability in copers may be indicative of a more adaptable motor synergy compared with individuals with chronic ankle instability.

Ankle Bracing Alters Coordination and Coordination Variability in Individuals With and Without Chronic Ankle Instability.

CONTEXT: Ankle bracing is an effective form of injury prophylaxis implemented for individuals with and without chronic ankle instability, yet mechanisms surrounding bracing efficacy remain in question. Ankle bracing has been shown to invoke biomechanical and neuromotor alterations that could influence lower-extremity coordination strategies during locomotion and contribute to bracing efficacy. OBJECTIVE: The purpose of this study was to investigate the effects of ankle bracing on lower-extremity coordination and coordination dynamics during walking in healthy individuals, ankle sprain copers, and individuals with chronic ankle instability. DESIGN: Mixed factorial design. SETTING: Laboratory setting. PARTICIPANTS: Forty-eight recreationally active individuals (16 per group) participated in this cross-sectional study. INTERVENTION: Participants completed 15 trials of over ground walking with and without an ankle brace. MAIN OUTCOME MEASURES: Coordination and coordination variability of the foot-shank, shank-thigh, and foot-thigh were assessed during stance and swing phases of the gait cycle through analysis of segment relative phase and relative phase deviation, respectively. RESULTS: Bracing elicited more synchronous, or locked, motion of the sagittal plane foot-shank coupling throughout swing phase and early stance phase, and more asynchronous motion of remaining foot-shank and foot-thigh couplings during early swing phase. Bracing also diminished coordination variability of foot-shank, foot-thigh, and shank-thigh couplings during swing phase of the gait cycle, indicating greater pattern stability. No group differences were observed. CONCLUSIONS: Greater stability of lower-extremity coordination patterns as well as spatiotemporal locking of the foot-shank coupling during terminal swing may work to guard against malalignment at foot contact and contribute to the efficacy of ankle bracing. Ankle bracing may also act antagonistically to interventions fostering functional variability.

Effects of Game Performance on Softball Pitchers and Catchers.

Oliver, GD, Plummer, HA, Washington, JK, Weimar, WH, and Brambeck, A. Effects of game performance on softball pitchers and catchers. J Strength Cond Res 33(2): 466-473, 2019-The purpose of this study was to examine the effects of game exposure on pitchers and catchers' hip and glenohumeral range of motion (ROM), isometric strength, and vertical jump performance and power. Five college female softball pitchers (174.24 ± 7.53 cm; 82.10 ± 11.27 kg; 20 ± 1.82 years) and 4 catchers (165.10 ± 9.04 kg; 68.61 ± 3.87 cm; 20 ± 1.41 years) participated. Hip and glenohumeral rotational ROM; hip and glenohumeral rotational isometric strength; hip abduction and adduction strength; and vertical jump height were assessed pre- and postgame exposure. The catchers displayed significantly greater throwing side hip internal rotation (IR) ROM (mean difference = +6.88°, p = 0.03) postgame exposure, whereas the pitchers exhibited less IR (mean difference = -2.02%, p = 0.013) and external rotation (ER; mean difference = -1.95%, p = 0.026) strength in the nonthrowing side hip pre vs. postgame exposure. The performance demands of pitchers and catchers vary greatly, causing position-specific decreases/increases in various tests following game performance. Pitchers exhibited significant decreases in nonthrowing side hip IR and ER strength. In catchers, throwing side hip IR ROM significantly increased following game exposure. Further evaluation of ROM, strength, and power is necessary as it is unknown how these changes following a game affect sports performance or risk of injury.

Local Pressure Application Effects on Neurological and Circulatory Function.

BACKGROUND: Pain and discomfort reported during sitting is a significant problem for aviators during prolonged missions. Previous work has determined that areas of local pressure exist during prolonged sitting in UH-60 seat systems; however, no work has examined the effects of this local pressure on measures of neurological and circulatory function. METHODS: A total of 30 healthy subjects completed the study in which focal pressure was applied in three conditions (no pressure, pressure to the ischial tuberosity, and pressure to the posterior thigh). We applied pressure using a purpose-built pressure application system allowing subjects to sit in a position mimicking the sitting position in a UH-60 Black Hawk helicopter and measurements were taken before, during, and after pressure application. We measured neurological function with the soleus Hoffmann reflex and sural nerve conduction velocity, and circulatory function with dynamic infrared thermography. RESULTS: We found a decrease in soleus Hoffmann reflex by 0.87 V and 0.52 V during pressure application at the posterior thigh and ischial tuberosity, respectively. No changes in nerve conduction velocity were found among the conditions during or after pressure application. Limb temperature increased 0.42-0.44°C during pressure application, but began to return to baseline once pressure was removed. DISCUSSION: This study examined the development of neurological and circulatory alterations due to local pressure application in an aviation specific functional position. These results may be used in the development of future interventions to mitigate the negative effects of localized pressure in military aviators.Games KE, Lakin JM, Quindry JC, Weimar WH, Sefton JM. Local pressure application effects on neurological and circulatory function. Aerosp Med Hum Perform. 2018; 89(8):693-699.

Local Pressure Application Effects on Discomfort, Temperature, and Limb Oxygenation.

INTRODUCTION: Despite significant investment into the development and improvement of military helicopter seat systems, military aviators continue to report seat system related pain and discomfort during prolonged missions. METHODS: Using a factorial repeated measures design, 15 healthy subjects completed the study, in which focal pressure was applied to two locations on the sitting surfaces of the body (ischial tuberosity and middle of the posterior thigh). Pressure was applied using a purpose-built pressure application system allowing subjects to sit in a position mimicking the sitting position in the UH-60 Black Hawk helicopter. The researchers measured pain using the Category Partitioning Scale and McGill Pain Questionnaire and vascular function using dynamic infrared thermography in the lower leg and pulse oximetry at the great toe. Data were collected before and during a 10-min application of focal pressure applied to either the ischial tuberosity or middle of the posterior thigh and at two different pressure magnitudes (36 or 44 kPa). RESULTS: We found that during a 10-min pressure application, superficial skin temperature increased by 0.61°C, suggesting a decreased venous return during pressure application. We found that lower extremity blood oxygenation remained unchanged during pressure application. Subjects' reported pain increased during pressure application and was greater with 44 kPa of application compared to 36 kPa. DISCUSSION: These results support the hypothesis that locally high pressure creates symptoms of discomfort and paresthesia. Research examining the effects of local pressure application on physiological and neurological function is needed. Games KE, Lakin JM, Quindry JC, Weimar WH, Sefton JM. Local pressure application effects on discomfort, temperature, and limb oxygenation. Aerosp Med Hum Perform. 2016; 87(8):697-703.

Post-exercise branched chain amino acid supplementation does not affect recovery markers following three consecutive high intensity resistance training bouts compared to carbohydrate supplementation.

BACKGROUND: Amino acid supplementation has been shown to potentially reduced exercise-induced muscle soreness. Thus, the purpose of this study was to examine if branched chain amino acid and carbohydrate (BCAACHO) versus carbohydrate-only sports drink (CHO) supplementation attenuated markers of muscle damage while preserving performance markers following 3 days of intense weight training. METHODS: Healthy resistance-trained males (n = 30) performed preliminary testing (T1) whereby they: 1) donated a baseline blood draw, 2) performed knee extensor dynamometry to obtain peak quadriceps isometric and isokinetic torque as well as electromyography (EMG) activity at 60°/s and 120°/s, and 3) performed a one repetition maximum (1RM) barbell back squat. The following week participants performed 10 sets x 5 repetitions at 80 % of their 1RM barbell back squat for 3 consecutive days and 48 h following the third lifting bout participants returned for (T2) testing whereby they repeated the T1 battery. Immediately following and 24 h after the three lifting bouts, participants were randomly assigned to consume one of two commercial products in 600 mL of tap water: 1) BCAAs and CHO (3 g/d L-leucine, 1 g/d L-isoleucine and 2 g/d L-valine with 2 g of CHO; n = 15), or 2) 42 g of CHO only (n = 15). Additionally, venous blood was drawn 24 h following the first and second lifting bouts and 48 h following the third bout to assess serum myoglobin concentrations, and a visual analog scale was utilized prior, during, and after the 3-d protocol to measure subjective perceptions of muscular soreness. RESULTS: There were similar decrements in 1RM squat strength and isokinetic peak torque measures in the BCAA-CHO and CHO groups. Serum myoglobin concentrations (p = 0.027) and perceived muscle soreness (p < 0.001) increased over the intervention regardless of supplementation. A group*time interaction was observed for monocyte percentages (p = 0.01) whereby BCAA-CHO supplementation attenuated increases in this variable over the duration of the protocol compared to CHO supplementation. CONCLUSION: BCAA-CHO supplementation did not reduce decrements in lower body strength or improve select markers of muscle damage/soreness compared to CHO supplementation over three consecutive days of intense lower-body training.

Improving performance by anchoring movement and "nerves".

Golf's governing bodies' recent decision to ban all putting styles "anchoring one end of the club against the body" bridges an important practical problem with psychological theory. We report the first experiment testing whether anchoring provides technical and/or psychological advantage in competitive performance. Many "greats" of professional golf from Arnold Palmer and Jack Nicklaus to Tiger Woods have argued against anchoring, believing that it takes "nerves" out of competitive performance and therefore artificially levels the playing field. To shed more light on the issue, we tested participants' performance with anchored and unanchored putters under low and high pressure when controlling for the putter length. We found no statistically significant evidence for a technical advantage due to anchoring but a clear psychological advantage: participants who anchored their putters significantly outperformed unanchored counterparts under high, but not low, pressure. Results provide tentative evidence for the ban's justification from a competitive standpoint. However, before any definite conclusions can be made, more research is needed when using high-level golfers.

Effects of a Simulated Game on Muscle Activation in Youth Baseball Pitchers.

It is generally accepted that playing with fatigue is a primary predictor of injury in youth baseball because muscular fatigue is believed to alter mechanics during the arm cocking and acceleration phases. Therefore, the purpose of this study was to quantitatively describe gluteal and upper extremity muscle activations in youth baseball pitchers during a simulated game. Twenty-three youth baseball players (11.2 ± 0.8 years; 151.4 ± 8.7 cm; 47.5 ± 10.8 kg) participated. Data were collected through a Delsys Bagnoli-8-channel electromyography system. Single differential electrodes (interelectrode distance: 10 mm) were attached to the bilateral gluteus maximus and medius and throwing side latissimus dorsi, lower trapezius, and serratus anterior and upper trapezius. After warm-up, participants were instructed to throw randomly provided game situations over a regulation distance (46 feet; 14.02 meters) to a catcher. Three, 4-seam fastballs for strikes, thrown in the first and last innings of the simulated game were selected for analysis. A multivariate analysis of variance revealed no statistically significant differences in muscle activity at the 3 phases of the throw, between first and last innings of the simulated game with an observed power of 0.274 (phase 1: foot contact to maximum shoulder external rotation), 0.297 (phase 2: maximum shoulder external rotation to ball release), and 0.226 (phase 3: ball release to maximum shoulder internal rotation). Examining muscle activations as a pitcher approaches fatigue provides information on how long a pitcher can perform before mechanical alterations occur. Although this study did not reveal significant changes, it did reiterate the fact that pitch counts may be working in possibly preventing a youth pitcher throwing to fatigue.

Hip and Shoulder Range of Motion in Youth Baseball Pitchers.

Oliver, GD and Weimar, WH. Hip and shoulder range of motion in youth baseball pitchers. J Strength Cond Res 30(10): 2823-2827, 2016-Lack of range of motion (ROM) has long been suspected as contributing to injury in baseball pitchers. However, all previous ROM research has focused on collegiate and professional pitchers. It was thus the purpose of this study to measure and evaluate bilateral hip and throwing shoulder rotational passive range of motion (PROM) in youth baseball pitchers. Twenty-six youth baseball pitchers (11.3 ± 1.0 years; 152.4 ± 9.0 cm; 47.5 ± 11.3 kg) with no history of injury participated. Bilateral hip and throwing shoulder rotational PROM was measured. There were no significant side-to-side differences for the hip variables (p ≥ 0.05). Shoulder external rotation (ER) was significantly greater than shoulder internal rotation (IR). And the lead leg hip had significantly greater ER than IR. Shoulder ER revealed significant correlations with both lead and stance hip IR (r = 0.45, p = 0.02 and r = 0.48, p = 0.01, respectively). The youth baseball pitchers in this study displayed similar PROM patterns as collegiate and professional baseball pitchers. Additionally, our youth baseball pitchers also presented strong relationships between hip and shoulder PROM. This study reveals that the PROM patterns displayed by these youth may indicate that their available ROM could survive maturation. It is therefore suggested that clinical focus be directed to maintaining hip and shoulder rotational ROM throughout maturation in attempt to determine a possible relations between injurious mechanisms and performance enhancement.

Ex-Vivo Evaluation of a Modified Teno Fix(®) Device Repair Pattern Versus a 3-Loop Pulley for Repair of Equine Flexor Tendons.

OBJECTIVE: To compare the load to ultimate failure, load to a 2 mm gap, mode of failure, and gap at failure (mm) of the Teno Fix(®) (TF) to the 3-loop pulley (3LP) for repair of equine tendon lacerations. The use of 4TF devices versus 5TF devices on load to ultimate failure and load to a 2 mm gap was also compared. STUDY DESIGN: Ex vivo biomechanical study; unbalanced incomplete block (horse) design. SAMPLES: Cadaveric equine forelimb superficial digital flexor tendon (n = 20 paired tendons). METHODS: Ten tendon pairs were selected randomly and repaired with a 3LP and 4TF pattern, and 10 tendon pairs repaired with a 3LP and 5TF pattern. Load to ultimate failure, load to a 2 mm gap, mode of failure, and gap at failure were obtained using materials testing. RESULTS: The 3LP had a significantly greater ultimate load to failure (P < .001, respectively) and a significantly higher load to a 2 mm gap than both TF repairs (P < .001, respectively). The most frequent mode of failure was suture pull-out for the 3LP and anchor pull-out for the TF. Gap at failure was significantly larger in the 3LP than both TF repairs (P < .001). The ultimate load to failure was significantly higher for the 5TF than the 4TF (P = .004) but there was no significant difference in load to a 2 mm gap, or gap at failure between both TF repairs (P = .11, P = .15, respectively). CONCLUSIONS: Neither TF repair was stronger than the 3LP in load to ultimate failure and load to a 2 mm gap. Addition of a fifth TF device significantly increased the load to ultimate failure but did effect the load to a 2 mm gap over the 4TF.

Prolonged restricted sitting effects in UH-60 helicopters.

INTRODUCTION: Advances in flight technologies and the demand for long-range flight have increased mission lengths for U.S. Army Black Hawk UH-60 crewmembers. Prolonged mission times have increased reports of pilot discomfort and symptoms of paresthesia thought to be due to UH-60 seat design and areas of locally high pressure. Discomfort created by the seat-system decreases situational awareness, putting aviators and support crew at risk of injury. Therefore, the purpose of this study was to examine the effects of prolonged restricted sitting in a UH-60 on discomfort, sensory function, and vascular measures in the lower extremities. METHODS: There were 15 healthy men (age = 23.4 ± 3.1 yr) meeting physical flight status requirements who sat in an unpadded, UH-60 pilot's seat for 4 h while completing a common cognitive task. During the session, subjective discomfort, sensory function, and vascular function were measured. RESULTS: Across 4 h of restricted sitting, subjective discomfort increased using the Category Partitioning Scale (30.27 point increase) and McGill Pain Questionnaire (8.53 point increase); lower extremity sensory function was diminished along the S1 dermatome; and skin temperature decreased on both the lateral (2.85°C decrease) and anterior (2.78°C decrease) aspects of the ankle. DISCUSSION: The results suggest that prolonged sitting in a UH-60 seat increases discomfort, potentially through a peripheral nervous or vascular system mechanism. Further research is needed to understand the etiology and onset of pain and paresthesia during prolonged sitting in UH-60 pilot seats. Games KE, Lakin JM, Quindry JC, Weimar WH, Sefton JM. Prolonged restricted sitting effects in UH-60 helicopters.

Gluteus medius and scapula muscle activations in youth baseball pitchers.

The baseball pitching motion is a total kinetic chain activity that must efficiently use both the upper and lower extremity. Of particular importance is the scapular motion, which is critical for humeral positioning and proper alignment of shoulder musculature. It was hypothesized that scapular stability is enhanced by pelvic girdle stability. Therefore, it was the purpose of this study to determine the muscle activations of selected pelvic and scapular stabilizing muscles during a fastball pitch in youth baseball pitchers. Twenty youth baseball pitchers (age: 11.3 + 1.0 years; height: 152.4 + 9.0 cm; weight: 47.5 + 11.3 kg) were recorded throwing 4-seam fastballs for strikes. Data revealed moderate (20-39% maximum voluntary isometric contraction [MVIC]) to moderately strong (>40% MVIC) activation of the ipsilateral (throwing arm side) gluteus medius, upper trapezius, and serratus anterior throughout phases 2 (maximum shoulder external rotation to ball release) and 3 (ball release to maximum shoulder internal rotation). Moderately strong activation (>40% MVIC) of the upper trapezius and serratus anterior was noted during phases 2 and 3 of the pitching motion. Pearson's product-moment correlation revealed significant relationships between bilateral gluteus medius and the force couples about the scapula during all 3 phases of the pitching motion. The results of this study provide important data that improve the understanding of the muscular relationship between the pelvic and scapular stabilizers during the fastball pitch. Training and rehabilitation programs should consider focusing on lumbopelvic-hip and scapular muscle strengthening as well as coordinated strengthening of the pelvic and scapular stabilizers, in baseball pitchers.

Balance and exposure to an elevated sloped surface.

Fall injuries and fatalities exceed 50 billion dollars annually. One half of fatal falls are from pitched roof settings. Falls from elevation in an occupational setting have been documented to be a significant issue in today's workforce. The purpose of this study was to investigate the influence of exposure to inclined surfaces on flat surface balance at varying heights above the ground. Thirty participants, 10 male college students (inexperienced), 10 female college students (inexperienced) and 10 male roofers (experienced) between age 19 and 50 years participated in this study. Participants walked for 20 min on an elevated roof segment (9-14 feet above ground level) and a ground level roof segment (0-5 feet above ground level) on separate days. Results indicated a significant difference for all groups in sway velocity over time at both levels (elevated and ground) and from eyes open to eyes closed conditions at both levels (p<0.05). Statistical analysis revealed that roofers had significantly less increase in sway velocity, post exposure than that of the inexperienced group (p<0.05). These findings provide practical information to employers and employees during the construction of structures that employ a pitched roof design. The implication of these findings include the knowledge that an individual is less stable directly after performing roofing tasks on a pitched roof setting, and should be afforded ample time to recover before moving into activities that would place them at a higher risk of injury from falls.

Difference in ratio of evertor to invertor activity between the dominant and nondominant legs during simulated lateral ankle sprain.

CONTEXT: The dominant and nondominant legs respond asymmetrically during landing tasks, and this difference may occur during an inversion perturbation and provide insight into the role of ankle-evertor and -invertor muscle activity. OBJECTIVE: To determine if there is a difference in the ratio of evertor to invertor activity between the dominant and nondominant legs and outer-sole conditions when the ankle is forced into inversion. DESIGN: Repeated-measures single-group design. SETTING: University laboratory. PARTICIPANTS: 15 physically active healthy volunteers with no previous history of an ankle sprain or lower extremity surgery or fracture. INTERVENTIONS: An outer sole with fulcrum was used to cause 25° of inversion at the subtalar joint after landing from a 27-cm step-down task. Participants performed 10 fulcrum trials on both the dominant and nondominant leg. MAIN OUTCOME MEASURES: The ratio of evertor to invertor muscle activity 200 ms before and 200 ms after the inversion perturbation was measured using electromyography. This ratio was the dependent variable. Independent variables included outer-sole condition (fulcrum, flat), leg (dominant, nondominant), and time (prelanding, postlanding). The data were analyzed with separate 2-way repeated-measures ANOVA, 1 for the prelanding ratios and 1 for the postlanding ratios. RESULTS: For the postlanding ratios, the fulcrum outer sole had a significantly greater (P < .05) ratio than the flat outer sole, and the nondominant leg had a significantly greater (P < .05) ratio than the dominant leg. CONCLUSIONS: These results indicate that a greater evertor response is produced when the ankle is forced into inversion, and a greater response is produced for the nondominant leg, which may function better during a postural-stabilizing task than the dominant leg.

Arch height index normative values of college-aged women using the arch height index measurement system.

BACKGROUND: The arch height index measurement system (AHIMS) device has been found to be a reliable and valid instrument for measuring the arch height index (AHI) of the feet of individuals; however, normative data for the AHI are lacking for various populations. Therefore, the purposes of this study were to establish population normative AHI values for college-aged females and to compare the observed AHI data across right and left feet. METHODS: Seventy-nine college-aged females served as study participants, and both feet were measured using the AHIMS in the seated and standing positions. The AHI was calculated as the ratio of the dorsum height of the foot at half the total foot length to the length of the foot from the heel to the base of the first metatarsophalangeal joint. RESULTS: The mean ± SD AHI values for the left and right feet in the seated position were 0.355 ± 0.031 and 0.369 ± 0.034, respectively. The mean ± SD AHI values for the left and right feet in the standing position were 0.338 ± 0.031 and 0.343 ± 0.033, respectively. There were significant differences observed between the left and right feet for the seated (P < .001) and standing (P = .003) positions. CONCLUSIONS: Normative values were established for college-aged females for the AHI using the AHIMS. Differences were noted between the right and left feet of the participants sampled. Although normative values were obtained, we caution against using these values to classify foot arch types based solely on a sample of the population studied.

Development of a fulcrum methodology to replicate the lateral ankle sprain mechanism and measure dynamic inversion speed.

When the ankle is forced into inversion, the speed at which this movement occurs may affect the extent of injury. The purpose of this investigation was to develop a fulcrum device to mimic the mechanism of a lateral ankle sprain and to determine the reliability and validity of the temporal variables produced by this device. Additionally, this device was used to determine if a single previous lateral ankle sprain or ankle taping effected the time to maximum inversion and/or mean inversion speed. Twenty-six participants (13 with history of a single lateral ankle sprain and 13 with no history of injury) completed the testing. The participants completed testing on three separate days, performing 10 trials with the fulcrum per leg on each testing day, and tape was applied to both ankles on one testing day. No significant interactions or main effects were found for either previous injury or ankle taping, but good reliability was found for time to maximum inversion (ICC = .81) and mean inversion speed (ICC = .79). The findings suggest that although neither variable was influenced by the history of a single previous lateral ankle sprain or ankle taping, both variables demonstrated good reliability and construct validity, but not discriminative validity.

Effects of previous lateral ankle sprain and taping on the latency of the peroneus longus.

The latency of the peroneus longus may be a key factor in the prevention of lateral ankle sprains (LASs). In addition, ankle taping is often applied to help prevent LASs. The purpose of this study was to determine the effects of a previous LAS and ankle taping on the latency of the peroneus longus after an inversion perturbation. Twenty-six participants, including 13 participants with no previous history of a LAS and 13 participants with a history of a single LAS completed the testing. Ankle taping was applied in a closed basket weave technique on one of the two testing days. The latency of the peroneus longus was determined by the onset of muscle activity exceeding 10 SD from baseline activity, after initiation of the 25 degrees inversion perturbation. A significant main effect (p < 0.05) was present for the ankle support condition, with ankle taping causing a significant reduction in latency of the peroneus longus (65.04 +/- 10.81 to 57.70 +/- 9.39 ms). There was no difference (p > 0.05) in latency between the injury groups. Ankle taping, immediately after application, reduces the latency of the peroneus longus among participants with and without a history of a LAS.