Continuous Tracking of Foot Strike Pattern during a Maximal 800-Meter Run.

(1) Background: Research into foot strike patterns (FSP) has increased due to its potential influence on performance and injury reduction. The purpose of this study was to evaluate changes in FSP throughout a maximal 800-m run using a conformable inertial measurement unit attached to the foot; (2) Methods: Twenty-one subjects (14 female, 7 male; 23.86 ± 4.25 y) completed a maximal 800-m run while foot strike characteristics were continually assessed. Two measures were assessed across 100-m intervals: the percentage of rearfoot strikes (FSP%RF), and foot strike angle (FSA). The level of significance was set to p ≤ 0.05; (3) Results: There were no differences in FSP%RF throughout the run. Significant differences were seen between curve and straight intervals for FSAAVE (F [1, 20] = 18.663, p < 0.001, ηp2 = 0.483); (4) Conclusions: Participants displayed decreased FSA, likely indicating increased plantarflexion, on the curve compared to straight intervals. The analyses of continuous variables, such as FSA, allow for the detection of subtle changes in foot strike characteristics, which is not possible with discrete classifiers, such as FSP%RF.

Increasing Step Rate Affects Rearfoot Kinematics and Ground Reaction Forces during Running.

Relatively high frontal and transverse plane motion in the lower limbs during running have been thought to play a role in the development of some running-related injuries (RRIs). Increasing step rate has been shown to significantly alter lower limb kinematics and kinetics during running. The purpose of this study was to evaluate the effects of increasing step rate on rearfoot kinematics, and to confirm how ground reaction forces (GRFs) are adjusted with increased step rate. Twenty runners ran on a force instrumented treadmill while marker position data were collected under three conditions. Participants ran at their preferred pace and step rate, then +5% and +10% of their preferred step rate while being cued by a metronome for three minutes each. Sagittal and frontal plane angles for the rearfoot segment, tibial rotation, and GRFs were calculated during the stance phase of running. Significant decreases were observed in sagittal and frontal plane rearfoot angles, tibial rotation, vertical GRF, and anteroposterior GRF with increased step rate compared with the preferred step rate. Increasing step rate significantly decreased peak sagittal and frontal plane rearfoot and tibial rotation angles. These findings may have implications for some RRIs and gait retraining.

Using A Soft Conformable Foot Sensor to Measure Changes in Foot Strike Angle During Running.

The potential association between running foot strike analysis and performance and injury metrics has created the need for reliable methods to quantify foot strike pattern outside the laboratory. Small, wireless inertial measurement units (IMUs) allow for unrestricted movement of the participants. Current IMU methods to measure foot strike pattern places small, rigid accelerometers and/or gyroscopes on the heel cap or on the instep of the shoe. The purpose of this study was to validate a thin, conformable IMU sensor placed directly on the dorsal foot surface to determine foot strike angles and pattern. Participants (n = 12) ran on a treadmill with different foot strike patterns while videography and sensor data were captured. Sensor measures were compared against traditional 2D video analysis techniques and the results showed that the sensor was able to accurately (92.2% success) distinguish between rearfoot and non-rearfoot foot strikes using an angular velocity cut-off value of 0°/s. There was also a strong and significant correlation between sensor determined foot strike angle and foot strike angle determined from videography analysis (r = 0.868, p < 0.001), although linear regression analysis showed that the sensor underestimated the foot strike angle. Conformable sensors with the ability to attach directly to the human skin could improve the tracking of human dynamics and should be further explored.

Physiological and Biomechanical Responses to Running on Lower Body Positive Pressure Treadmills in Healthy Populations.

BACKGROUND: Lower body positive pressure treadmills (LBPPTs) aim to reduce musculoskeletal loading during running. As LBPPTs have become more commercially available, they have become integrated into athletic performance and clinical rehabilitation settings. Consequentially, published research examining the biomechanical and physiological responses to unweighted running has increased. OBJECTIVE: The purpose of this systematic review was to synthesize the literature in an attempt to provide researchers and clinicians with a comprehensive review of physiologic and biomechanical responses to LBPPT running. METHODS: Through a generic search of PubMed, CINAHL, MEDLINE, and SPORTDiscus using a comprehensive list of search terms related to LBPPT, unweighting, and body weight support during running, we identified all peer-reviewed publications that included LBPPT running. Two reviewers independently evaluated the quality of studies using a modified Downs and Black checklist for non-randomized studies. RESULTS: A total of 15 articles met the inclusion criteria for this review. Peak and active vertical ground-reaction forces were consistently reduced with unweighting, but regional loading within the foot was also altered towards a forefoot strike. LBPPTs also provide some horizontal assistance. Neuromuscular activation is generally reduced with LBPPTs, but the stabilizer muscle groups may respond differently than the propulsive muscle groups. Submaximal heart rate and volume oxygen consumption are reduced with unweighting, but physiologic response remains generally unchanged at maximal intensities. CONCLUSIONS: The current literature suggests that LBPPTs are effective in allowing individuals to achieve a given metabolic stimulus with reduced musculoskeletal loading. However, LBPPTs not only reduce impact but also change neuromuscular activation and biomechanics in a complex manner. Thus, clinicians must account for the specific biomechanical and physiological alterations induced by LBPPTs when designing training programs and rehabilitation protocols.