Friberg Equation to Predict Pediatric Distal Forearm Fracture Remodeling.

BACKGROUND: This study is the first to test Friberg's equation's (Vt=V0[e]) accuracy in predicting the residual angular deformity in pediatric distal forearm fractures. METHODS: Angular deformities from distal forearm fractures in 50 children (mean age, 9 y) were retrospectively measured on follow-up radiographs once healed and compared to extrapolated angles at respective follow-up intervals from 2013 to 2015. RESULTS: The predicted and actual angulations from 120 radiographs (mean follow-up, 3mo) showed that the mean predicted angle was similar to the measured angle in the radioulnar plane and only 2 degrees greater than the measured angle in the dorsovolar plane. A strong correlation was observed between predicted and measured angles in both planes. CONCLUSIONS: Friberg's equation is a valid tool for predicting remodeling potential in pediatric distal 25% forearm fractures. LEVEL OF EVIDENCE: Prognostic Study-Level II.

Motoneuron Function Does not Change Following Whole-Body Vibration in Individuals With Chronic Ankle Instability.

CONTEXT: Following a lateral ankle sprain, ∼40% of individuals develop chronic ankle instability (CAI), characterized by recurrent injury and sensations of giving way. Deafferentation due to mechanoreceptor damage postinjury is suggested to contribute to arthrogenic muscle inhibition (AMI). Whole-body vibration (WBV) has the potential to address the neurophysiologic deficits accompanied by CAI and, therefore, possibly prevent reinjury. OBJECTIVE: To determine if an acute bout of WBV can improve AMI and proprioception in individuals with CAI. DESIGN AND PARTICIPANTS: The authors examined if an acute bout of WBV can improve AMI and proprioception in individuals with CAI with a repeated-measures design. A total of 10 young adults with CAI and 10 age-matched healthy controls underwent a control, sham, and WBV condition in randomized order. SETTING: Biomechanics laboratory. INTERVENTION: WBV. MAIN OUTCOME MEASURES: Motoneuron pool recruitment was assessed via Hoffmann reflex (H-reflex) in the soleus. Proprioception was evaluated using ankle joint position sense at 15° and 20° of inversion. Both were assessed prior to, immediately following, and 30 minutes after the intervention (pretest, posttest, and 30mPost, respectively). RESULTS: Soleus maximum H-reflex:M-response (H:M) ratios were 25% lower in the CAI group compared with the control group (P = .03). Joint position sense mean constant error did not differ between groups (P = .45). Error at 15° in the CAI (pretest 0.8 [1.6], posttest 2.0 [2.8], 30mPost 2.0 [1.9]) and control group (pretest 0.8 [2.0], posttest 0.6 [2.9], 30mPost 0.5 [2.1]) did not improve post-WBV. Error at 20° did not change post-WBV in the CAI (pretest 1.3 [1.7], posttest 1.0 [2.4], 30mPost 1.5 [2.2]) or control group (pretest -0.3 [3.0], posttest 0.8 [2.1], 30mPost 0.6 [1.8]). CONCLUSION: AMI is present in the involved limb of individuals with CAI. The acute response following a single bout of WBV did not ameliorate the presence of AMI nor improve proprioception in those with CAI.

The effect of wheelchair propulsion style on changes in time spent in extreme wrist orientations after a bout of fatiguing propulsion.

This study compared how wheelchair propulsion styles affect changes in percentage of time spent in extreme wrist orientations, which have been associated with median nerve injury, after a fatiguing bout of propulsion. Twenty novice, non-disabled adult males learned arcing (ARC) and semicircular (SEMI) propulsion styles and utilised each to perform a wheelchair fatigue protocol. ARC and SEMI did not significantly differ in terms of changes after the fatigue protocol in percentage of time spent in extreme flexion/extension or radial/ulnar deviation at the push phase beginning or end. A pattern was observed, although not significant, of greater increases in percentage of time spent in extreme wrist extension and ulnar deviation during the push phase beginning and ulnar deviation during the push phase end while utilising SEMI relative to ARC. This study evinces that individual differences are greater than observed changes in extreme wrist orientations for both propulsion styles. Practitioner Summary: How wheelchair propulsion styles change with fatigue in terms of extreme wrist orientations was examined. This study evinces that individual differences are greater than observed changes in extreme wrist orientations for both propulsion styles and point towards the need for future research on individual differences utilising propulsion styles.

Split-Belt Treadmill Walking Alters Lower Extremity Frontal Plane Mechanics.

Interventions that manipulate gait speed may also affect the control of frontal plane mechanics. Expanding the current knowledge of frontal plane adaptations during split-belt treadmill walking could advance our understanding of the influence of asymmetries in gait speed on frontal plane mechanics and provide insight into the breadth of adaptations required by split-belt walking (SBW). Thirteen young, healthy participants, free from lower extremity injury walked on a split-belt treadmill with belts moving simultaneously at different speeds. We examined frontal plane mechanics of the ankle, knee, and hip joints during SBW, as well as medio-lateral ground reaction forces (ML-GRF). We did not observe alterations in the frontal mechanics produced during early or late adaptation of SBW when compared to conditions where the belts moved together. We did observe that ML-GRF and hip moment impulse of the fast limb increased over time with adaptation to SBW. These results suggest this modality may provide a unique therapy for individuals with gait pathologies, impairments, or compensation(s).

Photobiomodulation delays the onset of skeletal muscle fatigue in a dose-dependent manner.

Photobiomodulation (PBM) therapy has been implicated as an effective ergogenic aid to delay the onset of muscle fatigue. The purpose of this study was to examine the dose-response ergogenic properties of PBM therapy and its ability to prolong time to task failure by enhancing muscle activity and delaying the onset of muscle fatigue using a static positioning task. Nine participants (24.3 ± 4.9 years) received three doses of near-infrared (NIR) light therapy randomly on three separate sessions (sham, 240, and 480 J). For the positioning task, participants held a 30 % one-repetition maximum (1-RM) load using the index finger until volitional fatigue. Surface electromyography (sEMG) of the first dorsal interosseous muscle was recorded for the length of the positioning task. Outcomes included time to task failure (TTF), muscle fatigue, movement accuracy, motor output variability, and muscle activity (sEMG). The 240-J dose significantly extended TTF by 26 % (p = 0.032) compared with the sham dose. TTF for the 240-J dose was strongly associated with a decrease in muscle fatigue (R (2) = 0.54, p = 0.024). Our findings show that a 240-J dose of NIR light therapy is efficacious in delaying the onset and extent of muscle fatigue during submaximal isometric positioning tasks. Our findings suggest that NIR light therapy may be used as an ergogenic aid during functional tasks or post-injury rehabilitation.

Comparison of metabolic cost, performance, and efficiency of propulsion using an ergonomic hand drive mechanism and a conventional manual wheelchair.

OBJECTIVE: To compare the metabolic cost (oxygen uptake per unit time [V˙o2 consumption], heart rate, and number of pushes), performance (velocity and distance traveled), and efficiency (oxygen uptake per distance traveled [Vo2 efficiency]) of propulsion using a novel ergonomic hand drive mechanism (EHDM) and a conventional manual wheelchair (CMW). DESIGN: Repeated-measures crossover design. SETTING: Semicircular track. PARTICIPANTS: Adult full-time manual wheelchair users with spinal cord injuries (N=12; mean age ± SD, 38.8±12.4y; mean body mass ± SD, 73.7±13.3kg; mean height ± SD, 173.6±11.1cm) who were medically and functionally stable and at least 6 months postinjury. INTERVENTION: Participants propelled themselves for 3.5 minutes at a self-selected pace in a CMW and in the same chair fitted with the EHDM. MAIN OUTCOME MEASURES: Velocity, distance traveled, number of pushes, V˙o2 consumption, Vo2 efficiency, and heart rate were compared by wheelchair condition for the last 30 seconds of each trial using paired t tests (α=.01). RESULTS: The CMW condition resulted in more distance traveled (33.6±10.8m vs 22.4±7.8m; P=.001), greater velocity (1.12±0.4m/s vs .75±.30m/s; P=.001), and better Vo2 efficiency (.10±.03mL·kg(-1)·m(-1) vs .15±.03mL·kg(-1)·m(-1); P<.001) than the EHDM condition, respectively. No significant differences were found between the 2 conditions for number of pushes (27.5±5.7 vs 25.7±5.4; P=.366), V˙o2 consumption (6.43±1.9mL·kg(-1)·min(-1) vs 6.19±1.7mL·kg(-1)·min(-1); P=.573), or heart rate (100.5±14.5 beats per minute vs 97.4±20.2 beats per minute; P=.42). CONCLUSIONS: The results demonstrate that metabolic costs did not differ significantly; however, performance and efficiency were sacrificed with the EHDM. Modifications to the EHDM (eg, addition of gearing) could rectify the performance and efficiency decrements while maintaining similar metabolic costs. Although not an ideal technology, the EHDM can be considered as an alternative mode of mobility by wheelchair users and rehabilitation specialists.

Validation of a cardiorespiratory fitness assessment for firefighters.

Currently, a submaximal protocol is used to measure cardiorespiratory fitness in firefighters by estimating their true aerobic capacity (V[Combining Dot Above]O2max); however, this submaximal test has not been cross-validated among firefighters. Thirty firefighters (85% male, 15% female), completed the submaximal protocol and the maximal (Bruce) treadmill protocol on separate occasions. Pearson's correlation analyses between the submaximal and Bruce protocol revealed a significant moderate positive correlation (r = 0.635, p = 0.005). The range of mean V[Combining Dot Above]O2max values and SDs produced from the submaximal and maximal protocols varied greatly (35.4-50.9 vs. 28.6-58.4 ml·kg·min, and SD of 3.91 vs. 7.22, respectively). The submaximal V[Combining Dot Above]O2 test underestimated the true V[Combining Dot Above]O2max in the majority of firefighters (72.4%) and overestimated the true V[Combining Dot Above]O2max in the remainder of firefighters. Participants with a higher body fat percentage were more likely (p = 0.0157) to have an overestimated true V[Combining Dot Above]O2max than those with a lower-body fat percentage. Our results indicate the current submaximal V[Combining Dot Above]O2 test used to measure cardiorespiratory fitness in firefighters is an improvement over previous protocols. However, our findings also show that the accuracy of this submaximal test for predicting the true V[Combining Dot Above]O2max in firefighters is questionable, and may not identify firefighters who possess substandard cardiorespiratory fitness, particularly in those with a higher percentage of body fat. Thus, the results of this study indicate that improvements to the current Fire Service Joint Management, Wellness & Fitness Initiative (WFI) V[Combining Dot Above]O2 assessment is still needed to accurately reflect the true V[Combining Dot Above]O2max of individual firefighters.

Cellular phone texting impairs gait in able-bodied young adults.

Cellular phone texting has become increasingly popular, raising the risk of distraction-related injuries. The purpose of this study was to compare alterations in gait parameters during normal gait as opposed to walking while texting. Thirty able-bodied young adults (age = 20 ± 2 y, height = 171 ± 40 cm, mass = 61.7 ± 11.2 kg) who reported texting on a regular basis were tested using an 11-camera optical motion capture system as they walked across an 8 m, obstacle-free floor. A reduction in velocity (P < .05) was seen along with additional significant changes in spatial and temporal parameters. Specifically, step width and double stance time increased, while toe clearance, step length, and cadence decreased. Although many of the changes in spatial and temporal parameters generally accompany slowed gait, the complex distraction task used here may have amplified these potentially deleterious effects. The combination of the slower gait velocity and decrease in attention to the surrounding environment suggests that an individual who is texting while walking could be at a greater risk of injury. Tripping injuries while texting could be more likely due to the decreased toe clearance. In addition, increased step width may increase the likelihood of stepping on an unstable surface or colliding with obstacles in close proximity.

Acute aquatic treadmill exercise improves gait and pain in people with knee osteoarthritis.

OBJECTIVE: To examine the acute effects of aquatic and land treadmill exercise on gait kinematics as well as the level of disease-specific and movement-related pain for individuals with osteoarthritis. DESIGN: Quasi-experimental crossover design. SETTING: Biomechanics laboratory. PARTICIPANTS: Participants (N=14; age, 43-64y) diagnosed with osteoarthritis at the knee (n=12), osteoarthritis at the knee and ankle (n=1), or osteoarthritis at the knee and hip (n=1). INTERVENTIONS: Participants performed 3 exercise sessions separated by at least 24 hours in 1 week for each mode of exercise (aquatic treadmill and land treadmill). MAIN OUTCOME MEASURES: Gait kinematics and pain were measured before and after each intervention. RESULTS: The angular velocity gain score during stance for left knee extension was improved by 38% after aquatic treadmill exercise (P=.004). Similarly, during swing, the gain scores for angular velocity were also greater for left knee internal rotation and extension by 65% and 20%, respectively (P=.004, P=.008, respectively). During stance, the joint angle gain score for left hip flexion was 7.23% greater after land exercise (P=.007). During swing, the angular velocity gain score for right hip extension was significantly greater for aquatic exercise by 28% (P=.01). Only the joint angle gain score for left ankle abduction during stance was significantly higher after land exercise (4.72%, P=.003). No other joint angle gain scores for either stance or swing were significantly different for either condition (P=.06-.96). Perceived pain was 100% greater after land than aquatic treadmill exercise (P=.02). Step rate and step length were not different between conditions (P=.31-.92). CONCLUSIONS: An acute training period on an aquatic treadmill positively influenced joint angular velocity and arthritis-related joint pain. Acute aquatic treadmill exercise may be useful as a conservative treatment to improve angular speed of the lower-extremity joints and pain related to osteoarthritis.

Oxygen consumption, oxygen cost, heart rate, and perceived effort during split-belt treadmill walking in young healthy adults.

During split-belt treadmill walking the speed of the treadmill under one limb is faster than the belt under the contralateral limb. This unique intervention has shown evidence of acutely improving gait impairments in individuals with neurologic impairment such as stroke and Parkinson's disease. However, oxygen use, heart rate and perceived effort associated with split-belt treadmill walking are unknown and may limit the utility of this locomotor intervention. To better understand the intensity of this new intervention, this study was undertaken to examine the oxygen consumption, oxygen cost, heart rate, and rating of perceived exertion associated with split-belt treadmill walking in young healthy adults. Fifteen participants completed three sessions of treadmill walking: slow speed with belts tied, fast speed with belts tied, and split-belt walking with one leg walking at the fast speed and one leg walking at the slow speed. Oxygen consumption, heart rate, and rating of perceived exertion were collected during each walking condition and oxygen cost was calculated. Results revealed that oxygen consumption, heart rate, and perceived effort associated with split-belt walking were higher than slow treadmill walking, but only oxygen consumption was significantly lower during both split-belt walking than fast treadmill walking. Oxygen cost associated with slow treadmill walking was significantly higher than fast treadmill walking. These findings have implications for using split-belt treadmill walking as a rehabilitation tool as the cost associated with split-belt treadmill walking may not be higher or potentially more detrimental than that associated with previously used treadmill training rehabilitation strategies.

The influence of sex, age and BMI on the degeneration of the lumbar spine.

Previous research on lumbar spine osteophyte formation has focused on patterned development and the relation of age and sex to degeneration within the vertebral bodies. The inclusion of osteophytes originating on the laminae and body mass index (BMI) may result in a more complete evaluation. This study investigates lumbar osteophyte development on the laminae and vertebral bodies to determine whether osteophyte development: (i) is related bilaterally, at different lumbar levels, and superior and inferior margins; (ii) on the laminae and vertebral bodies are reciprocally dependent responses; (iii) is correlated with sex, age and/or BMI. Seventy-six individuals (39 females, 37 males) were randomly selected from a modern skeletal collection (Bass Donated Collection). Osteophyte development was scored in eight regions on each vertebra at all five lumbar levels. A factor analysis considered all 40 scoring regions and Pearson's correlation analyses assessed the relatedness of age and BMI with the consequent factors. The factor analysis separated the variables into two similar factors for males and females defined as: (i) superior and inferior vertebral body scores and (ii) superior laminar scores at higher lumbar levels. The factor analysis also determined a third factor for females defined as: (iii) inferior laminar scores at lower lumbar levels. The severity of vertebral body osteophytes increased with age for both sexes. Additionally for females, as BMI increased, osteophyte severity increased for both the superior laminar margins higher in the column and the vertebral bodies. Dissimilarities between the factors in males and females and the correlation of BMI to osteophyte severity exclusively in females provide evidence for different biomechanical processes influencing osteophyte development.

Does acute whole-body vibration training improve the physical performance of people with knee osteoarthritis?

The purpose of this study was to determine the effects of a single session of whole-body vibration training (WBVT) on the physical performance of individuals with knee osteoarthritis (OA) in 3 tests designed to simulate activities of daily living (ADLs). Fifteen individuals with symptomatic knee OA completed the Timed-Up-and-Go Test, step test, 20-m walk test, and visual analog scale (VAS) recordings of knee pain intensity. A main effect was detected for time to complete the step test (F[2,28] = 6.243, p = 0.006, (Equation is included in full-text article.)). Post hoc analyses revealed that the time to complete the step test at 5 minutes after WBVT improved significantly (p = 0.042) from that of the pretest. A moderate correlation (r = 0.465, p = 0.001) was found between the VAS scores and the time to complete the step test across all trials. A main effect was found for time to complete the walk test (F[2,28] = 4.370, p = 0.022, (Equation is included in full-text article.)). Post hoc analyses did not indicate significant improvements from pretest seen at 5 minutes after WBVT (p = 0.110) and 1 hour after WBVT (p = 0.224). The WBVT was well tolerated in nearly all the participants, and we observed that an acute bout of WBVT was effective in improving the ability of individuals with knee OA to perform a step test and 20-m walk test. Our findings suggest that WBVT may be an effective nonpharmacologic modality to treat some knee OA symptoms and improve ADLs.

Physical capacity and functional abilities improve in young adults with intellectual disabilities after functional training.

Individuals with an intellectual disability (ID) have higher rates of obesity, lower rates of physical activity, cardiorespiratory fitness, and muscular endurance than do typically developed individuals (TDI) and are twice as likely to develop chronic disease, living half as long as TDIs do. The purpose of this study was to examine the improvements in physical capacity and functional ability in Special Olympic Athletes (SOAs) aged 19-22 years after participating in a functional training (FT) program and compare these scores with those of the SOAs in a resistance weight training (WT) program. Twenty SOAs (13 men, 7 women with mild to moderate ID) participated in a 1-hour FT program, twice a week, for 10 weeks, compared with 22 same-aged SOAs (14 men, 8 women) participating in a 1-hour WT program (2× week for 8 weeks). Prefitness and postfitness tests consisting of heart rate (HR) for the 3-minute step test, static plank, body weight squats, static bar hang, and knee push-ups were conducted. Two-tailed, paired sample t-tests (p < 0.05) were used to evaluate the differences in the FT group. Change scores were used to compare FTG with the WT group. The HR decreased by 31.8 b·min⁻¹ pre-post in the FTG (p < 0.001). Static plank duration improved by 22.4 seconds in the FTG (p = 0.016); static plank change scores improved (p = 0.037) for the FTG (26.5 ± 32.1 seconds compared with that for the WT group (4.6 ± 22 seconds). Height and weight values were unchanged in both the groups. The results of this study demonstrate the value of FT programs for this population, because weight equipment is not always available in many settings.

Pitching shoulder passive flexibility: torque-angle analysis for external rotation and internal rotation.

In this study, a custom device was developed to analyse the pitching shoulder's external rotation (ER) and internal rotation (IR) passive flexibility. We analysed three novel measures: the resistance onset angle (ROA = angle where the shoulder begins stretching), rotational stiffness, and torque at the end range of motion (ROM). The purpose was to conduct a bilateral analysis to determine if there are significant differences between the throwing and non-throwing shoulder. Participants were 30 upper level pitchers (13 division I, 17 minor league). During testing, pitchers laid supine on a treatment table and the arm was secured to a rotational wheel with the shoulder abducted 90° and elbow flexed 90°. Dependent t-tests revealed significant (p < 0.01) and relatively extreme bilateral differences for all three variables. The throwing shoulder had: increased ER ROA (9°), decreased IR ROA (5.3°), increased ER stiffness (17%), increased IR stiffness (34%), increased ER torque (21%), and increased IR torque (30%). Secondary correlation analysis was completed to determine if the torque-angle variables were good predictors of the end ROM. Stiffness correlations were weak for ER (r = 0.35, p = 0.048) and IR (r = 0.42, p = 0.017) but ROA correlations were strong for ER (r = 0.85, p < 0.001) and IR (r = 0.86, p < 0.001).

Carrying Asymmetric Loads While Walking on a Treadmill Interferes with Lower Limb Coordination.

The purpose of this study was to investigate the effect of different load carriage modes on coordinative patterns in the lower extremities during walking. Twenty-five university students walked on a treadmill at their preferred pace under three different load conditions: symmetric load (5% of body mass in messenger bags on each shoulder hanging vertically and against the hips), asymmetric load 1 (10% of body mass in a messenger bag on one shoulder hanging vertically against the ipsilateral hip), and asymmetric load 2 (10% of body mass in a messenger bag on one shoulder with the bag draped across the trunk to the contralateral hip). Altered thigh-shank and shank-foot couplings were found for the loaded side during the stance of gait when comparing the asymmetric 1 and 2 to the symmetric load. In addition, thigh-thigh coupling was changed during gait when comparing the asymmetric load 2 and symmetric load. However, we did not find any significant differences in intralimb and interlimb couplings between the two different asymmetric load conditions. The results suggest potential benefits when carrying symmetrical loads in order to decrease abnormal limb coordination in daily activities. Thus, it may be advisable to distribute load more symmetrically to avoid abnormal gait.

Supervised moderate intensity resistance exercise training improves strength in Special Olympic athletes.

The purpose of this study was to examine the effects of a moderate intensity resistance training program on Special Olympic athletes (SOAs) and similarly aged typically developed volunteers (TDs) who also served as coaches. Fifteen SOAs and 17 TDs participated (age range 19-24 years). The intervention consisted of resistance training: 1 set, 8-12 reps, over 10-12 sessions, on Med-X weight equipment. Exercises tested were seated row (SR), leg curl (LC), leg extension (LE), chest press (CP), and the abdominal crunch (AC). The weight lifted, and the amount of repetitions performed at the beginning and end of training, were used to determine the predicted 1 repetition max (1RM). A 2-way (2:group x 2:time) analysis of variance was computed for each exercise. Time main effects were detected, which indicated that predicted 1RM increased significantly for all participants. Specifically, these were the SR (F(1,30) = 99.238, p < 0.001); the LC (F(1,30) = 91.578, p < 0.001); the LE (F(1,30) = 83.253, p < 0.001); the CP (F(1,30) = 53.675, p < 0.001); and the AC (F(1,30) = 57.759, p < 0.001). The predicted 1RM values increased between 25 and 50% across the exercises tested. There were no group main effects or interactions. Thus, with minimal training time, both similar and significant strength gains can be accomplished by both SOAs and TDs, respectively. Supervised moderate intensity resistance training is recommended for the populations tested and may result in vocational and athletic performance gains.

Self-assessed disability and functional performance in individuals with and without ankle instability: a case control study.

STUDY DESIGN: Single-blind case-control study. OBJECTIVE: To compare functional performance and self-assessed disability scores among individuals with and without chronic ankle instability (CAI) and uninjured controls. BACKGROUND: After an acute lateral ankle sprain, CAI develops in 40% to 75% of all individuals. However, some individuals, copers, maintain high-level activities after an ankle sprain and do not develop CAI. Studying differences between copers and those with CAI is the first step in developing a clinical battery of tests that can accurately determine which individuals are more likely to develop CAI after an acute lateral ankle sprain. METHODS AND MEASURES: Participants were 24 active adults with unilateral CAI (mean +/- SD age, 21.7 +/- 2.8 years), 24 copers (20.8 +/- 1.5 years), and 24 uninjured controls (21.8 +/- 2.6 years). Participants completed 3 questionnaires of self-assessed disability: (1) Foot and Ankle Disability Index, (2) Foot and Ankle Disability Index-Sport, and (3) a questionnaire of ankle function. Four hop tests were also completed: (1) figure-8 hop, (2) side-to-side hop, (3) triple-crossover hop, and (4) single-leg hop for distance. RESULTS: Self-assessed disability was significantly different among groups (P<.001), but hop test scores (P = .259) were not. Those with CAI had greater self-assessed disability than copers and uninjured controls. Copers and uninjured controls did not differ in self-assessed disability or functional performance. CONCLUSIONS: Self-assessed disability is significantly greater in those with CAI than copersand uninjured controls. However, functional performance, measured by hop tests, did not differ among groups.

A biomechanical comparison of back and front squats in healthy trained individuals.

The strength and stability of the knee plays an integral role in athletics and activities of daily living. A better understanding of knee joint biomechanics while performing variations of the squat would be useful in rehabilitation and exercise prescription. We quantified and compared tibiofemoral joint kinetics as well as muscle activity while executing front and back squats. Because of the inherent change in the position of the center of mass of the bar between the front and back squat lifts, we hypothesized that the back squat would result in increased loads on the knee joint and that the front squat would result in increased knee extensor and decreased back extensor muscle activity. A crossover study design was used. To assess the net force and torque placed on the knee and muscle activation levels, a combination of video and force data, as well as surface electromyographic data, were collected from 15 healthy trained individuals. The back squat resulted in significantly higher compressive forces and knee extensor moments than the front squat. Shear forces at the knee were small in magnitude, posteriorly directed, and did not vary between the squat variations. Although bar position did not influence muscle activity, muscle activation during the ascending phase was significantly greater than during the descending phase. The front squat was as effective as the back squat in terms of overall muscle recruitment, with significantly less compressive forces and extensor moments. The results suggest that front squats may be advantageous compared with back squats for individuals with knee problems such as meniscus tears, and for long-term joint health.

Jump-landing direction influences dynamic postural stability scores.

The purpose of this investigation was to determine dynamic postural stability differences among forward, diagonal, and lateral single leg-hop-stabilization protocols in healthy subjects. A one-within repeated measures design was used to determine the effects of jump direction on dynamic postural stability during landing. Subjects were required to perform a two-legged forward, diagonal, and lateral jump to a height equivalent to 50% of their maximum vertical leap, land on a single leg and balance for three seconds. Twenty-six subjects [10 males (22+/-3.9 years of age, 70.9+/-7.6kg, and 176.8+/-6.5cm) and 16 females (20.6+/-.5 years of age, 65.6+/-9.1kg, and 166.4+/-5.9cm)] volunteered to participate in this investigation. Dynamic postural stability indices for the anterior/posterior, medial/lateral, and vertical planes were collected during jump-landing trials of each direction. The results of the investigation show that medial/lateral and vertical dynamic postural stability were significantly affected by the direction of the jump. More specifically, lateral and diagonal jump-landings produce increased medial/lateral stability index (MLSI) scores and forward jump-landings produce increased vertical stability index (VSI) scores. The results suggest that in a healthy population, jump protocol direction will statistically affect dynamic postural stability in the frontal and vertical planes. These alterations could be exacerbated in individuals with lower extremity impairments and further research is warranted.

Developing reliable measures of the passive torque-angle relationship for shoulder internal and external rotation: Implications for overhead athletics.

OBJECTIVES: 1) Thoroughly assess shoulder flexibility by establishing the passive torque-angle relationship for internal and external rotation with the arm in an overhead athletics position (abducted 90°) and 2) test the reliability of four passive torque-angle measures. DESIGN: Reliability study. SETTING: Data were collected in a university biomechanics laboratory. PARTICIPANTS: Bilateral shoulder flexibility of 15 male college students (20.7 ±â€¯1.1 y) was evaluated twice in two sessions over 7-10 days. MAIN OUTCOME MEASURES: For both ER and IR, reliability was assessed bilaterally (intra-session, inter-session, and inter-tester) for the traditional range of motion measure and three novel kinetic measures: torque at end ROM, resistance onset angle, rotational stiffness. This resulted in 48 total assessments. RESULTS: Thirty-four assessments had good to excellent reliability (ICC ≥ 0.8), 10 had fair reliability (0.7 ≤ ICC < 0.8), and 4 had poor reliability (ICC< 0.7). Three of the four flexibility measures had a good overall ICC score: ROM (0.83), torque at end ROM (0.84), and resistance onset angle (0.81). The fourth, stiffness, had a fair overall reliability score (0.74). CONCLUSIONS: The passive torque-angle measures should be assimilated into clinical and research settings to determine the relevance to injury, rehabilitation, and performance.