Make an impact: going full circle together.

Sport diversification provides opportunities for individuals to develop physical literacy, establish a growth mindset, become more agile in varied environments, and develop robust strategies to improve performance. One could say the same for biomechanists, who study the control and dynamics of human movements in the context of sport. Through the lens of sport, we have focused on the ongoing interaction between the nervous system, musculoskeletal system, and the environment by using integrated experimental and modelling approaches to study well-practiced, goal-directed tasks in controlled laboratory and realistic field settings. By integrating multiple sources of information in real time to provide timely, relevant, usable, and easy to understand (TRUE) feedback during skill acquisition, we have found these resources also support learning and opportunities for self-discovery of proficiencies by coaches and athletes. Managing multimodal data acquired with emerging technological advances has also benefited from the use of FAIR data management principles, where data are findable, accessible, interoperable, and reusable. By listening, clarifying goals, and exploring together with coaches and athletes, we can bridge the gaps between what we know and what we do.

Towards a Remote Patient Monitoring Platform for Comprehensive Risk Evaluations for People with Diabetic Foot Ulcers.

Diabetic foot ulcers (DFUs) significantly affect the lives of patients and increase the risk of hospital stays and amputation. We suggest a remote monitoring platform for better DFU care. This system uses digital health metrics (scaled from 0 to 10, where higher scores indicate a greater risk of slow healing) to provide a comprehensive overview through a visual interface. The platform features smart offloading devices that capture behavioral metrics such as offloading adherence, daily steps, and cadence. Coupled with remotely measurable frailty and phenotypic metrics, it offers an in-depth patient profile. Additional demographic data, characteristics of the wound, and clinical parameters, such as cognitive function, were integrated, contributing to a comprehensive risk factor profile. We evaluated the feasibility of this platform with 124 DFU patients over 12 weeks; 39% experienced unfavorable outcomes such as dropout, adverse events, or non-healing. Digital biomarkers were benchmarked (0-10); categorized as low, medium, and high risk for unfavorable outcomes; and visually represented using color-coded radar plots. The initial results of the case reports illustrate the value of this holistic visualization to pinpoint the underlying risk factors for unfavorable outcomes, including a high number of steps, poor adherence, and cognitive impairment. Although future studies are needed to validate the effectiveness of this visualization in personalizing care and improving wound outcomes, early results in identifying risk factors for unfavorable outcomes are promising.

Generation of forward angular impulse with different initial conditions.

Generation of angular impulse during foot contact is regulated by controlling the relative orientation between the total body center of mass (CoM) and the reaction force (RF) applied to the feet. Between-task differences in initial CoM horizontal momentum were hypothesized to alter how forward angular impulse was generated during two forward translating tasks. Five skilled athletes performed standing (SFS) and running (RFS) forward somersaulting dives. Sagittal plane kinematics and RFs were obtained during the take-off phase of both tasks. The initial CoM momentum differences resulted in significant differences in control of the CoM relative to the RF, RF generation mechanisms, and knee and hip net joint moments (NJMs). During the RFS, angular impulse was generated by positioning the feet anterior to the CoM at initial contact so that the RF passed posterior to the CoM throughout the take-off phase. During the SFS, angular impulse was generated by positioning the CoM anterior to the feet prior to the push interval so that the RF passed posterior to the CoM. Task-specific differences in segment kinematics and RF direction contributed to the redistribution of knee and hip NJMs. These results suggest that initial conditions influence strategies the nervous system uses to satisfy task objectives.

Impairments in the mechanical effectiveness of reactive balance control strategies during walking in people post-stroke.

People post-stroke have an increased risk of falls compared to neurotypical individuals, partly resulting from an inability to generate appropriate reactions to restore balance. However, few studies investigated the effect of paretic deficits on the mechanics of reactive control strategies following forward losses of balance during walking. Here, we characterized the biomechanical consequences of reactive control strategies following perturbations induced by the treadmill belt accelerations. Thirty-eight post-stroke participants and thirteen age-matched and speed-matched neurotypical participants walked on a dual-belt treadmill while receiving perturbations that induced a forward loss of balance. We computed whole-body angular momentum and angular impulse using segment kinematics and reaction forces to quantify the effect of impulse generation by both the leading and trailing limbs in response to perturbations in the sagittal plane. We found that perturbations to the paretic limb led to larger increases in forward angular momentum during the perturbation step than perturbations to the non-paretic limb or to neurotypical individuals. To recover from the forward loss of balance, neurotypical individuals coordinated reaction forces generated by both legs to decrease the forward angular impulse relative to the pre-perturbation step. They first decreased the forward pitch angular impulse during the perturbation step. Then, during the first recovery step, they increased the backward angular impulse by the leading limb and decreased the forward angular impulse by the trailing limb. In contrast to neurotypical participants, people post-stroke did not reduce the forward angular impulse generated by the stance limb during the perturbed step. They also did not increase leading limb angular impulse or decrease the forward trailing limb angular impulse using their paretic limb during the first recovery step. Lastly, post-stroke individuals who scored poorer on clinical assessments of balance and had greater motor impairment made less use of the paretic limb to reduce forward momentum. Overall, these results suggest that paretic deficits limit the ability to recover from forward loss of balance. Future perturbation-based balance training targeting reactive stepping response in stroke populations may benefit from improving the ability to modulate paretic ground reaction forces to better control whole-body dynamics.

Regulation of Forward Angular Impulse in Tasks With Backward Translation.

Studying how elite athletes satisfy multiple mechanical objectives when initiating well-practiced, goal-directed tasks provides insights into the control and dynamics of whole-body movements. This study investigated the coordination of multiple body segments and the reaction force (RF) generated during foot contact when regulating forward angular impulse in backward translating tasks. Six highly skilled divers performed inward somersaults (upward and backward jump with forward rotation) and inward timers (upward and backward jump without rotation) from a stationary platform. Sagittal plane kinematics and RFs were recorded simultaneously during the takeoff phase. Regulation of the forward angular impulse was achieved by redirecting the RF about the total body center of mass. Significantly more backward-directed RF was observed during the first and second peak horizontal RF of the inward somersaults than the inward timers. Modulation of the horizontal RF altered the RF direction about the center of mass and the lower-extremity segments. Backward leg and forward trunk orientation and a set of relatively large knee extensor and small hip flexor net joint moments were required for forward angular impulse generation. Understanding how the forward angular impulse is regulated in trained individuals provides insights for clinicians to consider when exploring interventions related to fall prevention.

Reaction Force Generation and Mechanical Demand Imposed on the Shoulder When Initiating Manual Wheelchair Propulsion and at Self-Selected Fast Speeds.

Manual wheelchair (WC) users with spinal cord injury (SCI) experience shoulder pain and fatigue associated with their increased reliance on the upper extremity during activities of daily living (Bayley et al. 1987, "The Weight-Bearing Shoulder. The Impingement Syndrome in Paraplegics," J. Bone Jt. Surg. Am., 69(5), pp. 676-678). We hypothesized that the mechanical demand imposed on the shoulder, represented as resultant shoulder net joint moment (NJM) impulse, would be greater when initiating manual WC propulsion from a stationary position without momentum than when manually propelling at speed on a level sidewalk. Thirty manual WC users with paraplegia participated. Each individual initiated manual WC propulsion from a stationary position and propelled on a level sidewalk at their self-selected fast speed. Upper extremity kinematics and pushrim reaction forces (RFs) were measured and upper extremity joint kinetics were calculated and compared (α = 0.05) between cycle 1, initiated without momentum, and cycle 3 with momentum. Results indicate that multiple factors contributing to the mechanical demand imposed on the shoulder were significantly greater when manual WC propulsion was initiated without momentum than with momentum. Significant differences in resultant shoulder NJM impulse, push duration, orientation of RF relative to forearm, and resultant average shoulder NJMs during push were observed between momentum conditions. No significant differences in average resultant RF during push were found. These results indicate that mechanical loading of the shoulder during manual WC propulsion differs between momentum conditions; these differences in resultant shoulder NJM impulse during push need to be considered when assessing shoulder load exposure in stop-and-start activities.

Generation of Linear Impulse During the Takeoff of the Long Jump.

This study investigates the effect of initial leg angle on horizontal jump performance. Eleven highly skilled male and female long jumpers (national and Olympic level) performed a series of horizontal jumps for distance. Within-jumper differences in initial leg angle, normalized horizontal and net vertical impulses, contact time, and average reaction force during the impact interval, post-impact interval, and in total were measured using highspeed video (240 or 300 Hz) and a force plate (1200 Hz). Pearson correlations, Winsorized correlations, and the HC4 method were used to determine significant correlations between variables (α = 0.05). Within-jumper analysis indicated that when jumpers initiate the takeoff phase with a larger leg angle they are able to generate significantly greater negative horizontal and positive net vertical impulse (n = 7). Increased impulse generation was the result of increased contact time (n = 5 of 7) and / or increased average reaction force (n = 4) during the impact interval (n = 3) and / or post-impact interval (n = 4), depending on the individual. Initial leg configuration at contact and individual specific impulse generation strategies are important to consider when determining how an athlete with initial momentum can increase impulse generation to jump for distance.

Regulation of Linear and Angular Impulse during the Golf Swing with Modified Address Positions.

Golf shots off uneven terrain often require modifications in address position to complete the swing successfully. This study aimed to determine how golf players coordinate the legs to regulate linear and angular impulse (about an axis passing vertically through the center of mass) while modifying the lower extremity address position during the swing. Nine highly skilled golf players performed swings with a 6-iron under the Normal, Rear Leg Up and Target Leg Up conditions. Components of linear and angular impulse generated by the rear and target legs (resultant horizontal reaction force, resultant horizontal reaction force angle, and moment arm) were quantified and compared across the group and within a player (α = .05). Net angular impulse did not change between conditions. Target leg angular impulse was greater in the Target Leg Up condition than Rear Leg Up condition. Regulation of linear and angular impulse generation occurred while increasing stance width and redirecting resultant horizontal reaction forces to be more parallel to the target line under modified address positions. Net linear impulse perpendicular to the target was near zero or slightly posterior. Net linear impulse parallel to the target was less toward the target in the Target Leg Up condition compared to Normal and Rear Leg Up conditions. These results indicate individuals utilized player specific mechanisms to coordinate the legs and regulate impulse generation during the golf swing under modified address positions.

Data Analyses When Sample Sizes Are Small: Modern Advances for Dealing With Outliers, Skewed Distributions, and Heteroscedasticity.

The paper reviews advances and insights relevant to comparing groups when the sample sizes are small. There are conditions under which conventional, routinely used techniques are satisfactory. But major insights regarding outliers, skewed distributions, and unequal variances (heteroscedasticity) make it clear that under general conditions they provide poor control over the type I error probability and can have relatively poor power. In practical terms, important differences among groups can be missed and poorly characterized. Many new and improved methods have been derived that are aimed at dealing with the shortcomings of classic methods. To provide a conceptual basis for understanding the practical importance of modern methods, the paper reviews some modern insights related to why methods based on means can perform poorly. Then some strategies for dealing with nonnormal distributions and unequal variances are described. For brevity, the focus is on comparing 2 independent groups or 2 dependent groups based on the usual difference scores. The paper concludes with comments on issues to consider when choosing from among the methods reviewed in the paper.

Coordination of lower extremity multi-joint control strategies during the golf swing.

This study aimed to understand how players coordinate the multi-joint control strategies of the rear and target legs to satisfy the lower extremity and whole-body mechanical objectives during the golf swing when hitting shots with different clubs. Highly skilled golf players (n = 10) performed golf swings with a 6-iron and a driver. Joint kinetics were calculated using ground reaction forces and segment kinematics to determine net joint moments (NJMs) during the interval of interest within the downswing. Between club difference in NJMs and 3D support moments were compared across the group and within a player. Although player-specific multi-joint control strategies arose, players generally increased target leg ankle, knee, and hip NJMs when hitting with the driver while maintaining the relative contribution to the 3D support moment. Multi-joint control strategies used to control the target and rear legs were found to be different, yet the majority of the 3D support moment was produced by NJMs about an axis perpendicular to the leg planes. These results emphasize the importance of recognizing how an individual player coordinates multi-joint control from each leg, and highlights the need to design interventions that are player and leg specific to aid in improving player performance.

Lower extremity control during turns initiated with and without hip external rotation.

The pirouette turn is often initiated in neutral and externally rotated hip positions by dancers. This provides an opportunity to investigate how dancers satisfy the same mechanical objectives at the whole-body level when using different leg kinematics. The purpose of this study was to compare lower extremity control strategies during the turn initiation phase of pirouettes performed with and without hip external rotation. Skilled dancers (n=5) performed pirouette turns with and without hip external rotation. Joint kinetics during turn initiation were determined for both legs using ground reaction forces (GRFs) and segment kinematics. Hip muscle activations were monitored using electromyography. Using probability-based statistical methods, variables were compared across turn conditions as a group and within-dancer. Despite differences in GRFs and impulse generation between turn conditions, at least 90% of each GRF was aligned with the respective leg plane. A majority of the net joint moments at the ankle, knee, and hip acted about an axis perpendicular to the leg plane. However, differences in shank alignment relative to the leg plane affected the distribution of the knee net joint moment when represented with respect to the shank versus the thigh. During the initiation of both turns, most participants used ankle plantar flexor moments, knee extensor moments, flexor and abductor moments at the push leg׳s hip, and extensor and abductor moments at the turn leg׳s hip. Representation of joint kinetics using multiple reference systems assisted in understanding control priorities.

Whole-Body Balance Regulation during the Turn Phase of Piqué and Pirouette Turns with Varied Rotational Demands.

OBJECTIVE: To compare dancers' balance regulation at the whole-body level under increased rotational demands during the turn phase of turns with and without large center-of-mass (CM) translation (i.e., piqué vs pirouette turns). METHODS: Ten dancers performed single and double piqué and pirouette turns while kinematics and reaction forces were measured. During the turn phase, initial CM velocity, vertical alignment of the CM, mean braking force, and moment about the CM were compared across turn conditions using within-subject (Cliff's analog of Wilcoxon-Mann-Whitney test, adjusted for multiple comparisons) and group (sign test) statistical methods. RESULTS: For both single and double turns, the piqué turn phase was initiated with a significantly larger CM velocity towards the base of support than during the pirouette, consistent with the mechanical objectives of the turn. Additionally, during the turn phases of both single and double turns, the CM during the pirouette turns was more vertically aligned with the base of support than it was during the piqué turns. As rotational demand increased in both turns, the reaction forces were regulated in two ways to minimize the CM horizontal velocity as it approached vertical alignment with the base of support. By controlling the braking force and moment applied about the CM early during the turn phase, the potential for the CM to remain vertically aligned with the base of support increased. These findings can assist development of training tools geared towards balance regulation during pirouette and piqué turns.

Modification of Impulse Generation During Pirouette Turns With Increased Rotational Demands.

This study determined how dancers regulated angular and linear impulse during the initiation of pirouettes of increased rotation. Skilled dancers (n = 11) performed single and double pirouette turns with each foot supported by a force plate. Linear and angular impulses generated by each leg were quantified and compared between turn types using probability-based statistical methods. As rotational demands increased, dancers increased the net angular impulse generated. The contribution of each leg to net angular impulse in both single and double pirouettes was influenced by stance configuration strategies. Dancers who generated more angular impulse with the push leg than with the turn leg initiated the turn with the center of mass positioned closer to the turn leg than did other dancers. As rotational demands increased, dancers tended to increase the horizontal reaction force magnitude at one or both feet; however, they used subject-specific mechanisms. By coordinating the generation of reaction forces between legs, changes in net horizontal impulse remained minimal, despite impulse regulation at each leg used to achieve more rotations. Knowledge gained regarding how an individual coordinates the generation of linear and angular impulse between both legs as rotational demand increased can help design tools to improve that individual's performance.

Modification of impulse generation during piqué turns with increased rotational demands.

During initiation of a piqué turn, a dancer generates impulse to achieve the desired lateral translation and whole-body rotation. The goal of this study was to determine how individuals regulate impulse generation when initiating piqué turns with increased rotational demands. Skilled dancers (n=10) performed single (∼360°) and double (∼720°) piqué turns from a stationary position. Linear and angular impulse generated by the push and turn legs were quantified using ground reaction forces and compared across turn conditions as a group and within a dancer using probability-based statistical methods. The results indicate that as the rotation demands of the piqué turn increased, the net angular impulse generated increased whereas net lateral impulse decreased. Early during turn initiation, the free moment contributed to angular impulse generation. Later during turn initiation, horizontal reaction forces were controlled to generate angular impulse. As rotational demands increased, the moment applied increased primarily from redirection of the horizontal reaction force (RFh) at the push leg and a combination of RFh magnitude and moment arm increases at the turn leg. RFh at each leg were coordinated to limit unwanted net linear impulse. Knowledge of observed subject-specific mechanisms is important to inform the design of turning performance training tools.

Angular Impulse and Balance Regulation During the Golf Swing.

Our aim was to determine how skilled players regulate linear and angular impulse while maintaining balance during the golf swing. Eleven highly-skilled golf players performed swings with a 6-iron and driver. Components contributing to linear and angular impulse generated by the rear and target legs (resultant horizontal reaction force [RFh], RFh-angle, and moment arm) were quantified and compared across the group and within a player (α = .05). Net angular impulse generated by both the rear and target legs was greater for the driver than the 6-iron. Mechanisms used to regulate angular impulse generation between clubs varied across players and required coordination between the legs. Increases in net angular impulse with a driver involved increases in target leg RFh. Rear leg RFh-angle was maintained between clubs whereas target leg RFh became more aligned with the target line. Net linear impulse perpendicular to the target line remained near zero, preserving balance, while net linear impulse along the target line decreased in magnitude. These results indicate that the net angular impulse was regulated between clubs by coordinating force generation of the rear and target legs while sustaining balance throughout the task.

Compensatory strategies during manual wheelchair propulsion in response to weakness in individual muscle groups: A simulation study.

BACKGROUND: The considerable physical demand placed on the upper extremity during manual wheelchair propulsion is distributed among individual muscles. The strategy used to distribute the workload is likely influenced by the relative force-generating capacities of individual muscles, and some strategies may be associated with a higher injury risk than others. The objective of this study was to use forward dynamics simulations of manual wheelchair propulsion to identify compensatory strategies that can be used to overcome weakness in individual muscle groups and identify specific strategies that may increase injury risk. Identifying these strategies can provide rationale for the design of targeted rehabilitation programs aimed at preventing the development of pain and injury in manual wheelchair users. METHODS: Muscle-actuated forward dynamics simulations of manual wheelchair propulsion were analyzed to identify compensatory strategies in response to individual muscle group weakness using individual muscle mechanical power and stress as measures of upper extremity demand. FINDINGS: The simulation analyses found the upper extremity to be robust to weakness in any single muscle group as the remaining groups were able to compensate and restore normal propulsion mechanics. The rotator cuff muscles experienced relatively high muscle stress levels and exhibited compensatory relationships with the deltoid muscles. INTERPRETATION: These results underline the importance of strengthening the rotator cuff muscles and supporting muscles whose contributions do not increase the potential for impingement (i.e., the thoracohumeral depressors) and minimize the risk of upper extremity injury in manual wheelchair users.

Modifications in Wheelchair Propulsion Technique with Speed.

OBJECTIVE: Repetitive loading of the upper limb joints during manual wheelchair (WC) propulsion (WCP) has been identified as a factor that contributes to shoulder pain, leading to loss of independence and decreased quality of life. The purpose of this study was to determine how individual manual WC users with paraplegia modify propulsion mechanics to accommodate expected increases in reaction forces (RFs) generated at the pushrim with self-selected increases in WCP speed. METHODS: Upper extremity kinematics and pushrim RFs were measured for 40 experienced manual WC users with paraplegia while propelling on a stationary ergometer at self-selected free and fast propulsion speeds. Upper extremity kinematics and kinetics were compared within subject between propulsion speeds. Between group and within-subject differences were determined (α = 0.05). RESULTS: Increased propulsion speed was accompanied by increases in RF magnitude (22 of 40, >10 N) and shoulder net joint moment (NJM, 15 of 40, >10 Nm) and decreases in pushrim contact duration. Within-subject comparison indicated that 27% of participants modified their WCP mechanics with increases in speed by regulating RF orientation relative to the upper extremity segments. CONCLUSIONS: Reorientation of the RF relative to the upper extremity segments can be used as an effective strategy for mitigating rotational demands (NJM) imposed on the shoulder at increased propulsion speeds. Identification of propulsion strategies that individuals can use to effectively accommodate for increases in RFs is an important step toward preserving musculoskeletal health of the shoulder and improving health-related quality of life.