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

Abstract

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.