Development of a multidimensional military readiness assessment.

There is a need to be able to accurately evaluate whether an injured service member is able to return to duty. An effective assessment would challenge and measures physical and cognitive performance in a military-relevant context. Current assessments are lacking in one or more of these aspects. The simulation and data capture abilities of virtual reality systems are promising for use as the basis of multidimensional assessments. The team has previously developed a military-specific assessment in the Computer Assisted Rehabilitation Environment (CAREN) called the Readiness Evaluation During simulated Dismounted Operations (REDOp). Due to notable limitations in the original assessment, we have developed the next iteration, REDOp2. The assessment is able to challenge and measure a broader range of physical and cognitive performance domains in a more streamlined fashion. While limited to facilities with a CAREN, REDOp2 has the potential to provide an effective tool for highly trained and experienced wounded service members that require thorough assessment prior to returning to duty to ensure the safety of the team and mission. This methods paper describes the specific limitations in REDOp, how they were addressed in REDOp2, and suggested next steps to prepare the assessment for implementation.

Fall Prevention Training for Service Members With an Amputation or Limb Salvage Following Lower Extremity Trauma.

INTRODUCTION: Recent military conflicts have resulted in a significant number of lower extremity injuries to U.S. service members that result in amputation or limb preservation (LP) procedures. Service members receiving these procedures report a high prevalence and deleterious consequences of falls. Very little research exists to improve balance and reduce falls, especially among young active populations such as service members with LP or limb loss. To address this research gap, we evaluated the success of a fall prevention training program for service members with lower extremity trauma by (1) measuring fall rates, (2) quantifying improvements in trunk control, and (3) determining skill retention at 3 and 6 months after training. MATERIALS AND METHODS: Forty-five participants (40 males, mean [±SD] age, 34 ± 8 years) with lower extremity trauma (20 with unilateral transtibial amputation, 6 with unilateral transfemoral amputation, 5 with bilateral transtibial amputation, and 14 with unilateral LP procedures) were enrolled. A microprocessor-controlled treadmill was used to produce task-specific postural perturbations which simulated a trip. The training was conducted over a 2-week period and consisted of six 30-minute sessions. The task difficulty was increased as the participant's ability progressed. The effectiveness of the training program was assessed by collecting data before training (baseline; repeated twice), immediately after training (0 month), and at 3 and 6 months post-training. Training effectiveness was quantified by participant-reported falls in the free-living environment before and after training. Perturbation-induced recovery step trunk flexion angle and velocity was also collected. RESULTS: Participants reported reduced falls and improved balance confidence in the free-living environment following the training. Repeated testing before training revealed that there were no pre-training differences in trunk control. The training program improved trunk control following training, and these skills were retained at 3 and 6 months after training. CONCLUSION: This study showed that task-specific fall prevention training reduced falls across a cohort of service members with diverse types of amputations and LP procedures following lower extremity trauma. Importantly, the clinical outcome of this effort (i.e., reduced falls and improved balance confidence) can lead to increased participation in occupational, recreational, and social activities and thus improved quality of life.

Flotation-Restricted Environmental Stimulation Technique: A Proposed Therapy for Improving Performance and Recovery in Special Forces Operators - A Narrative Review.

The flotation-restriction environmental stimulation technique (FR) may have utility as a recovery tool for improving performance in elite competitive athletes and Special Operations Forces Operators (SOs). Studies suggest that FR may ameliorate various neurophysiological disorders and improve performance in recreational and elite athletic populations. We sought to understand whether there is evidence to support the use of FR to enhance physiological and psychological performance parameters in the SO population and to provide postulations as to the mechanisms of action of FR therapy. We performed an online literary search of publications dating from 1982 to 2021 and identified 34 sources addressing the aims, depending on population and condition or conditions, being treated. The reported physiological and psychological benefits of FR range from immediate to lasting 4 months. Overall, eight to twelve FR treatment sessions of from 40 to 90 minutes each may provide variable long-term benefits. The associated synergistic benefits of FR may be attributed to its thermal, chemical, and mechanical effects but deserve further exploration. Based on the current evidence, FR may serve as an effective performance-recovery therapy for improving pain, sleep, and performance measures (e.g., marksmanship and physical performance) in trained, untrained, and healthy adults. Future research focusing on FR as a unimodal recovery intervention is warranted in a specialized group of SOs.

Military training alters the fractal behavior of step width.

Non-linear analyses have been successfully applied to gait with evidence that fractal behavior of gait-related variables provide insights into function. Specifically, shifts in the fractal behavior of step width from pink toward white noise reflects a loss of complexity and diminished adaptive capacity and functionality. We previously reported an apparent difference in the fractal behavior of step width during treadmill walking between Service members with transtibial amputations and able-bodied civilian. We now combine recently collected data and data from two previous studies to further explore the relationship between lower limb injury, military service, and step width fractal behavior. Service member, regardless of the presence or type of injury, demonstrate step width fractal behavior walked in a way that the fractal behavior of their gait was significantly closer to white noise (-0.5 dB/Hz2) than uninjured civilians (-0.82 dB/Hz2). This data suggests that military training/service leads to a change in step width fractal behavior. Further studies are needed to explore what may cause this difference and any implications this may have on stability or performance.

Common fall-risk indicators are not associated with fall prevalence in a high-functioning military population with lower limb trauma.

BACKGROUND: Persons with lower limb trauma are at high risk for falls. Although there is a wide range of measures used to assess stability and fall-risk that include performance measures, temporal-spatial gait parameters, and nonlinear dynamic stability calculations, these measures are typically derived from fall-prone populations, such as older adults. Thus, it is unclear if these commonly used fall-risk indicators are effective at evaluating fall-risk in a younger, higher-functioning population of Service members with lower limb trauma. METHODS: Twenty-one Service members with lower limb trauma completed a battery of fall-risk assessments that included performance measures (e.g., four-square-step-test), and gait parameters (e.g., step width, step length, step time) and dynamic stability measures (e.g., local divergence exponents) during 10 min of treadmill walking. Participants also reported the number of stumbles and falls over the previous 4 weeks. Negative Binomial and Quasibinomial Regressions were used to evaluate the strength of associations between fall-risk indicators and self-reported falls. FINDING: Participants reported on average stumbling 6(4) times and falling 2(3) times in the previous 4 weeks. At least one fall was reported by 62% of the participants. None of the fall-risk indicators were significantly associated with fall prevalence in this population of Service members with lower limb trauma (p > 0.1). INTERPRETATION: Despite the high number of reported falls in this young active population, none of the fall-risk indicators investigated effectively captured and quantified the fall-risk. Further research is needed to identify appropriate fall-risk assessments for young, high-functioning individuals with lower limb trauma.

Novel Metrics for Assessing Mobility During Ground-Standing Transitions.

INTRODUCTION: Transitioning between the ground and standing is a required activity for many professions including skilled trades, law enforcement, and military service. However, available assessments are limited and focus primarily on quality of movement. Thus, we developed two novel assessments of functional mobility specific for ground-to-standing transitions: Stand-Prone-Standx2 (SPS2) and Stand-Kneel-Standx2 (SKS2-L/R) tests. The purpose of this study was to determine the psychometrics of these two new measures in able-bodied (AB) service members and in service members with unilateral lower extremity injury (LEI). MATERIALS AND METHODS: A total of 57 AB service members and 31 service members with a traumatic unilateral LEI wearing a custom carbon-fiber ankle-foot orthosis participated in this study. In total, 36 AB and 18 LEI participants returned for a second session to assess intersession reliability. Intraclass correlation coefficients were calculated for intersession and inter-rater comparisons (two-way random model for consistency and single measure). Additionally, performance was compared between legs and groups. RESULTS: The SPS2 and SKS2 assessments demonstrated excellent inter-rater and intersession reliability in both the AB and LEI groups with all intraclass correlation coefficient values greater than 0.8. Further, the tests were responsive to deficits associated with LEI, with the LEI group having significantly longer times on all assessments compared to the AB group. CONCLUSIONS: The SPS2 and SKS2 performance measures were found to have excellent inter-rater and intersession reliability in both AB participants and participants with LEI. Further, participants with LEI performed significantly slower than the AB participants. Excellent reliability and responsiveness to deficits associated with LEI support the use of the SPS2 and SKS2 to assess mobility in individuals with LEI. Transitions between the ground and standing occur in many occupational and daily tasks. These reliable performance measures that assess ground-to-stand transitions can be applied widely, in many populations beyond highly functioning service members with LEI.

Physiological and Psychological Stressors Affecting Performance, Health, and Recovery in Special Forces Operators: Challenges and Solutions. A Scoping Review.

INTRODUCTION: Special Operations Forces (SOF) Operators (SOs) are exposed to high levels of physiological and cognitive stressors early in their career, starting with the rigors of training, combined with years of recurring deployments. Over time, these stressors may degrade SOs' performance, health, and recovery. OBJECTIVES: (1) To evaluate sources identifying and describing physiological and psychological stressors affecting performance, health, and recovery in SOs, and (2) to explore interventions and phenomena of interest, such as the biological mechanisms of overtraining syndrome (OTS). METHODS: This review followed the recommendations and methodology of the Joanna Briggs Institute and the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. A database search from December 1993 to December 2021 was performed in PubMed, the Cochrane Library, and the Defense Technical Information Center (DTIC). Potential articles were identified using search terms from their titles, abstracts, and full texts. Articles effectively addressing the review questions and objectives were eligible. RESULTS: After 19 articles were excluded for not meeting established inclusion criteria, a total of 92 full-text articles were assessed for eligibility. After the final analysis, 72 articles were included. CONCLUSIONS: Allostatic imbalance may occur when supra-maximal demands are prolonged and repeated. Without adequate recovery, health and performance may decline, leading to nonfunctional overreaching (NFO) and OTS, resulting in harmful psychological and hormonal disruptions. The recurring demands placed on SOs may result in a chronically high burden of physical and mental stress known as allostatic overload. Future investigation, especially in the purview of longitudinal implementation, health, and recovery monitoring, is necessary for the health and readiness of the SOF population.

IMU filter settings for high intensity activities.

BACKGROUND: Recommendations for cut-off frequencies for inertial measurement units (IMU) are either based on marker-based motion analysis or based on low intensity activities. The selection of filter cut-off frequencies can impact the extracted variables from the filtered signal. There are no recommendations for IMU filter settings when collecting biomechanical data of high intensity activities. RESEARCH QUESTION: What are appropriate IMU cut-off frequency filter settings for high intensity activities? METHODS: Ten unimpaired participants were studied during controlled postural perturbations using a microprocessor-controlled treadmill. Disturbances were delivered in forward and backward directions and incrementally increased in both directions until the participant was unable to maintain an upright posture and the trial resulted in a fall. An IMU was placed on their sternum to obtain trunk sagittal kinematics. Custom code was implemented to estimate trunk angle, angular velocity, and linear acceleration about the flexion-extension axis in the trunk IMU coordinate system. The three trials that resulted in falls in each direction for each participant (60 total trials) were analysed. These trials were limited to 500 msec of the disturbance period. The cut-off frequency was calculated for trunk kinematics using 99 percent of the energy spectrum (E99). RESULTS: The trunk flexion angle (4 ± 4 Hz) and linear acceleration (35 ± 10 Hz) cut-off frequencies agreed with previously reported values. The cut-off frequency for trunk flexion angular velocity (26 ± 7 Hz) was higher than values previously reported. SIGNIFICANCE: Selection of cut-off frequency should be based on segment accelerations and not simply activity or segment of interest. Deliberate selection and reporting of filter settings in biomechanics research will improve data quality, reliability of inferences, and reproducibility of studies.

Assessments of trunk postural control within a fall-prevention training program for service members with lower limb trauma and loss.

BACKGROUND: Trunk postural control (TPC) is critical in maintaining balance following perturbations (i.e., avoiding falls), and impaired among persons with lower extremity trauma, contributing to elevated fall risk. Previously, a fall-prevention program improved TPC in individuals with unilateral transtibial amputation following trip-inducing perturbations. However, it is presently unclear if these improvements are task specific. RESEARCH QUESTION: Do improvements to TPC gained from a fall-prevention program translate to another task which assesses TPC in isolation (i.e., unstable sitting)? Secondarily, can isolated TPC be used to identify who would benefit most from the fall-prevention program? METHODS: Twenty-five individuals (21 male/4 female) with lower extremity trauma, who participated in a larger fall-prevention program, were included in this analysis. Trunk flexion and flexion velocity quantified TPC following perturbation; accelerometer-based sway parameters quantified TPC during unstable sitting. A generalized linear mixed-effects model assessed training-induced differences in TPC after perturbation; a generalized linear model assessed differences in sway parameters following training. Spearman's rho related training-induced changes to TPC following perturbation (i.e., the difference in TPC measures at pre- and post-training assessments) with pre- vs. post-training changes to sway parameters during unstable sitting (i.e., the difference in sway parameters at pre- and post-training assessments) as well as pre-training sway parameters with the pre- vs. post-training differences in TPC following perturbation. RESULTS: Following training, trunk flexion angles decreased, indicating improved TPC; however, sway parameters did not differ pre- and post-training. In addition, pre- vs. post-training differences in TPC following perturbation were neither strongly nor significantly correlated with sway parameters. Moreover, pre-training sway parameters did not correlate with pre- vs. post-training differences in trunk flexion/flexion velocity. SIGNIFICANCE: Overall, these results indicate that improvements to TPC gained from fall-prevention training are task-specific and do not translate to other activities. Moreover, isolated TPC measures are not able to identify individuals that benefit most from the fall-prevention program.

Inclusion of a Military-specific, Virtual Reality-based Rehabilitation Intervention Improved Measured Function, but Not Perceived Function, in Individuals with Lower Limb Trauma.

INTRODUCTION: Lower extremity injury is common in the military and can lead to instability, pain, and decreased function. Military service also places high physical demands on service members (SMs). Standard treatment interventions often fail to align with these unique demands. Thus, the goal of the study was to evaluate the effectiveness of a military-specific virtual reality-based rehabilitation (VR) intervention supplemental to standard care (SC) in improving military performance in SMs with lower extremity injuries. MATERIALS AND METHODS: As part of an institutional review board-approved randomized control trial, SMs receiving care at an advanced rehabilitation center were randomized to receive either SC or VR in addition to SC (VR+SC). Participants were evaluated before treatment and ∼3 weeks later using a previously developed and validated military-specific assessment. Perceived improvement in physical function was measured using a Global Rating of Change (GROC) questionnaire. A repeated measures ANOVA was used to evaluate the effects of adding VR on the military-specific assessment measures. Linear regression was used to determine the relationship between perceived improvement, measured improvement, and VR volume. RESULTS: The VR+SC group was able to traverse a greater distance in the assessment following the VR intervention. There was no significant difference in GROC between groups. For the VR+SC group, change in distance completed was not correlated with GROC, but GROC was correlated with VR volume. CONCLUSION: VR improved the distance that participants were able to traverse in the assessment. However, the VR+SC group demonstrated a disconnect between their perceived functional improvement as measured by the GROC and functional improvement as measured by the change in the distance completed. Rather, the perceived improvement appears to be more correlated with the volume of VR received. The way in which the treatment progression is structured and communicated may influence how patients perceive their change in physical function.

A novel assessment for Readiness Evaluation during Simulated Dismounted Operations: A reliability study.

OBJECTIVE: To determine the intersession reliability of the Readiness Evaluation during Simulated Dismounted Operations (REDOp), a novel ecologically-based assessment for injured Service Members, provide minimal detectable change values, and normative reference range values. To evaluate the ability to differentiate performance limitations between able-bodied and injured individuals using the REDOp. DESIGN: Repeated measures design and between group comparison. SETTING: Outpatient rehabilitative care setting. PARTICIPANTS: Service Members who were able-bodied (n = 32) or sustained a traumatic lower extremity injury (n = 22). INTERVENTIONS: During the REDOp, individuals walked over variable terrain as speed and incline progressively increased; they engaged targets; and carried military gear. MAIN OUTCOME MEASURES: Endurance measured using total distance traveled; walking stability measured using range of full-body angular momentum; and shooting accuracy, precision, reaction time and acquisition time. RESULTS: Intersession reliability analyses were conducted on a sub-group of 18 able-bodied Service Members. Interclass correlation coefficient values were calculated for distance traveled (0.91), range of angular momentum about three axes (0.78-0.93), shooting accuracy (0.61), precision (0.47), reaction time (0.21), and acquisition time (0.77). Service Members with lower extremity injury demonstrated significantly less distance traveled with a median distance of 0.89 km compared to 2.73 km for the able-bodied group (p < 0.001). Service Members with lower extremity injury demonstrated significantly less stability in the frontal and sagittal planes than the able-bodied group (p < 0.001). The primary performance limiter was endurance followed by pain for both groups. There was no evidence of ceiling effects. CONCLUSIONS: The REDOp is a highly reliable, military-relevant assessment that can be used to measure performance and identify deficits across the domains of activity tolerance, gait stability, and shooting performance.

A manual physical therapy intervention for symptoms of knee osteoarthritis and associated fall risk: A case series of four patients.

BACKGROUND AND PURPOSE: Patients with knee osteoarthritis (OA) are at an increased risk of falling. Further, the symptoms associated with knee OA are correlated with fall risk. A manual physical therapy (MPT) approach consisting of mobilizing techniques and reinforcing exercise improves the symptoms and functional limitations associated with knee OA. The purpose of this case series is to evaluate an MPT intervention of mobilization techniques and exercise for knee OA on improving symptoms and quantify the secondary benefit of improving stumble recovery. CASE DESCRIPTION: Four patients with symptomatic knee OA and four matched controls completed a fall risk assessment. Following 4 weeks of intervention, patients were reevaluated. OUTCOMES: Initial Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores indicated notable symptoms and functional limitations in all patients. In addition, all patients displayed elevated fall risk and/or impaired stumble responses. Following 4 weeks of intervention, all patients reported meaningful reductions in all three WOMAC subscales and demonstrated improvements in at least two of the three fall risk measures. DISCUSSION: We identified potential connections between symptom relief in patients with knee OA, stumble response, and ultimately fall risk. The results suggest that MPT intervention designed to improve the signs and symptoms of knee OA may lead to a secondary benefit of improved gait stability and stumble response.

Healthy individuals are more maneuverable when walking slower while navigating a virtual obstacle course.

INTRODUCTION: Maintaining stability, especially in the mediolateral direction, is important for successful walking. Navigating in the community, however, may require people to reduce stability to make quick lateral transitions, creating a tradeoff between stability and maneuverability. Walking slower can improve stability during steady state walking, but there remains a need to better understand how walking speed influences maneuverability. This study investigated how walking at different speeds influenced how individuals modulate both stability and maneuverability in a virtual obstacle course. METHODS: Fifteen healthy adults walked on a treadmill in a virtual environment for 6 trials each at typical and slower speed. Participants made repeated transitions between virtual sets of arches displayed in any of 4 lanes. Participants were instructed to walk under the arches and hit as few arches as possible. To quantify stability, mean step width and mean lateral margin of stability (Mean MOS) were calculated and averaged for ipsilateral and contralateral steps. To quantify maneuverability, the number of arches hit when entering or exiting each arch set was calculated and averaged for each condition. RESULTS: Participants exhibited high levels of variability in their stepping patterns. Mean MOS and mean step width were significantly greater for the typical speed than slower speed for the ipsilateral steps (p < 0.001). Participants hit more arches during the typical speed than during the slow speed (p = 0.039). CONCLUSION: When walking at the slower speed, healthy individuals exhibited decreased stability of ipsilateral steps, but increased maneuverability and better transition performance.

Use of Perturbation-Based Gait Training in a Virtual Environment to Address Mediolateral Instability in an Individual With Unilateral Transfemoral Amputation.

BACKGROUND AND PURPOSE: Roughly 50% of individuals with lower limb amputation report a fear of falling and fall at least once a year. Perturbation-based gait training and the use of virtual environments have been shown independently to be effective at improving walking stability in patient populations. An intervention was developed combining the strengths of the 2 paradigms utilizing continuous, walking surface angle oscillations within a virtual environment. This case report describes walking function and mediolateral stability outcomes of an individual with a unilateral transfemoral amputation following a novel perturbation-based gait training intervention in a virtual environment. CASE DESCRIPTION: The patient was a 43-year-old male veteran who underwent a right transfemoral amputation 7+ years previously as a result of a traumatic blast injury. He used a microprocessor-controlled knee and an energy storage and return foot. OUTCOMES: Following the intervention, multiple measures indicated improved function and stability, including faster self-selected walking speed and reduced functional stepping time, mean step width, and step width variability. These changes were seen during normal level walking and mediolateral visual field or platform perturbations. In addition, benefits were retained at least 5 weeks after the final training session. DISCUSSION: The perturbation-based gait training program in the virtual environment resulted in the patient's improved walking function and mediolateral stability. Although the patient had completed intensive rehabilitation following injury and was fully independent, the intervention still induced notable improvements to mediolateral stability. Thus, perturbation-based gait training in challenging simulated environments shows promise for improving walking stability and may be beneficial when integrated into a rehabilitation program.

Ramp Angle, Not Plateau Height, Influences Transition Strategies.

In a previous study, we found that participants modified how they transitioned onto and off of ramp configurations depending upon the incline. While the transition strategies were originally attributed to ramp angles, it is possible that the plateau influenced the strategies since the final surface height also differed. Ultimately, for the current study, we hypothesized that an individual's transition strategies would have significant main effects for ramp angle, but not plateau height. Twelve healthy, young adults transitioned onto 3 distinct ramp configurations, a 2.4-m ramp angled at 12.5° ending at a plateau height of 53 cm, a 1.2-m ramp angled at 23.5° ending at a plateau height of 53 cm, and a 2.4-m ramp angled at 23.5° ending at a plateau height of 99.5 cm. Kinematics, kinetics, and muscle activity were measured during the stance phase before contacting the ramp. In support of our hypothesis, impact peak, active peak, and all of the muscle activity variables had a significant main effect for ramp angle, with greater vertical force peaks and muscle activity on steeper ramp transitions. These findings support our previous interpretation that individuals use estimations of ramp angle, not plateau height, to determine their transition strategies.

Mediolateral angular momentum changes in persons with amputation during perturbed walking.

Over 50% of individuals with lower limb amputation fall at least once each year. These individuals also exhibit reduced ability to effectively respond to challenges to frontal plane stability. The range of whole body angular momentum has been correlated with stability and fall risk. This study determined how lateral walking surface perturbations affected the regulation of whole body and individual leg angular momentum in able-bodied controls and individuals with unilateral transtibial amputation. Participants walked at fixed speed in a Computer Assisted Rehabilitation Environment with no perturbations and continuous, pseudo-random, mediolateral platform oscillations. Both the ranges and variability of angular momentum for both the whole body and both legs were significantly greater (p<0.001) during platform oscillations. There were no significant differences between groups in whole body angular momentum range or variability during unperturbed walking. The range of frontal plane angular momentum was significantly greater for those with amputation than for controls for all segments (p<0.05). For the whole body and intact leg, angular momentum ranges were greater for patients with amputation. However, for the prosthetic leg, angular momentum ranges were less for patients than controls. Patients with amputation were significantly more affected by the perturbations. Though patients with amputation were able to maintain similar patterns of whole body angular momentum during unperturbed walking, they were more highly destabilized by the walking surface perturbations. Individuals with transtibial amputation appear to predominantly use altered motion of the intact limb to maintain mediolateral stability.

Older Adult Hill Transition Strategies are Determined by Task Demands and Cautious Gait Patterns.

Falls are the leading cause of injury for all age groups. However, adults over 65 are at a higher risk, with one-third falling each year. Transitioning between level and hill surfaces poses a greater fall risk than walking on either surface alone. Previous studies found that young adults adopted a cautious gait pattern to mitigate this risk. As older adults typically employ a cautious pattern during level walking, we investigated how they modify their gait pattern to safely transition between surfaces. Twenty adults over the age of 65 transitioned onto and off of a 15° ramp while we recorded kinematics and muscle activity. During the level-to-downhill and uphill-to-level transitions, participants took slower, shorter steps indicative of an exaggerated cautious gait pattern. The older adults also exhibited greater muscle activity during the transitions, which may be due to muscle weakness requiring compensatory strategies to meet the greater demands of the task. However, the slower, shorter steps when transitioning from uphill to level suggest that these compensations may not always be adequate. Thus, it is important to consider the relationship between physical abilities and task demands in evaluating walking terrains that may be excessively difficult or dangerous for older adults.

Segment lengths influence hill walking strategies.

Segment lengths are known to influence walking kinematics and muscle activity patterns. During level walking at the same speed, taller individuals take longer, slower strides than shorter individuals. Based on this, we sought to determine if segment lengths also influenced hill walking strategies. We hypothesized that individuals with longer segments would display more joint flexion going uphill and more extension going downhill as well as greater lateral gastrocnemius and vastus lateralis activity in both directions. Twenty young adults of varying heights (below 155 cm to above 188 cm) walked at 1.25 m/s on a level treadmill as well as 6° and 12° up and downhill slopes while we collected kinematic and muscle activity data. Subsequently, we ran linear regressions for each of the variables with height, leg, thigh, and shank length. Despite our population having twice the anthropometric variability, the level and hill walking patterns matched closely with previous studies. While there were significant differences between level and hill walking, there were few hill walking variables that were correlated with segment length. In support of our hypothesis, taller individuals had greater knee and ankle flexion during uphill walking. However, the majority of the correlations were between tibialis anterior and lateral gastrocnemius activities and shank length. Contrary to our hypothesis, relative step length and muscle activity decreased with segment length, specifically shank length. In summary, it appears that individuals with shorter segments require greater propulsion and toe clearance during uphill walking as well as greater braking and stability during downhill walking.

Pregnant women exaggerate cautious gait patterns during the transition between level and hill surfaces.

Falls are the leading cause of nonfatal injury across all age groups and a common incident for pregnant women. Thus, there is a critical demand for research to evaluate if walking strategies in pregnant women change throughout pregnancy in order to effectively intervene and minimize the incidence rate. The aim of the present study was to analyze modifications in temporal-spatial parameters as well as muscle activity during hill walking transitions in pregnant women between gestational week 20 and 32. Based upon previous literature, we hypothesized that in comparison to level walking, the transition strides of pregnant women would be distinct between trimesters in order to accommodate the physical changes within twelve weeks. Thirteen pregnant women completed a series of randomly assigned walking conditions on level and hill surfaces during gestational week 20 and 32. Our results demonstrated that pregnant women modulated their gait patterns throughout pregnancy with additional joint flexion as well as muscle activity at the ankle, knee and hip. In summary, pregnant women exaggerate cautious gait patterns by walking slower and wider with greater joint flexion and muscle activity in order to safely transition between level and hill surfaces.

Preferred step frequency during downhill running may be determined by muscle activity.

It is well established that metabolic cost is minimized at an individual's running preferred step frequency (PSF). It has been proposed that the metabolic minimum at PSF is due to a tradeoff between mechanical factors, however, this ignores muscle activity, the primary consumer of energy. Thus, we hypothesized that during downhill running, total muscle activity would be greater with deviations from PSF. Specifically, we predicted that slow step frequencies would have greater stance activity while fast step frequencies would have greater swing activity. We collected metabolic cost and leg muscle activity data while 10 healthy young adults ran at 3.0m/s for 5 min at level and downhill at PSF and ±15% PSF. In support of our hypothesis, there was a significant main effect for step frequency for both metabolic cost and total muscle activity. In addition, there was greater muscle activity in the stance phase during the slower step frequency while muscle activity was greater in the swing phase during the fast step frequency. This suggests that PSF is partially determined by the tradeoff between the greater cost of muscle activity in the swing phase and lower cost in the stance phase with faster step frequency.