title: Simulated hypergravity running increases skeletal and cardiovascular loads.
abstract: OBJECTIVE
  Eight recreational and eight competitive athletes were studied to determine the cardiovascular and musculoskeletal effects of running in hypergravity conditions simulated by the use of lower body negative pressure (LBNP). Subjects are sealed in a LBNP chamber with the use of a flexible, neoprene waist seal and the chamber pressure is reduced to provide an increased vertical force.
  
  
  METHODS
  Subjects ran on a treadmill at 1.0, 1.1, and 1.2 times body weight (BW) with increased loads provided by LBNP. Heart rate (HR), oxygen consumption (VO(2)), vertical ground reaction force (GRF), dynamic knee range of motion (ROM), and the electrical activities (EMG) of the tibialis anterior, medial gastrocnemius, vastus medialis obliquous, and biceps femoris muscles were measured.
  
  
  RESULTS
  LBNP produced a significant increase in HR at the 1.1-BW and 1.2-BW levels in both recreational and competitive athletes when compared with the 1.0 BW condition. Both VO(2) and GRF were increased significantly at 1.2 BW. No significant changes were observed in knee ROM or peak EMG amplitude with LBNP in either recreational or competitive athletes.
  
  
  CONCLUSIONS
  Increased HR and VO(2) indicate an increased cardiovascular load whereas increased GRF indicates an increased skeletal load. The lack of change in muscle activation and knee ROM point to a preservation in gait mechanics. Increased cardiovascular and skeletal loads with preservation of gait mechanics suggest that exercise within LBNP may be an effective training modality to improve athletic performance.
authors.affiliation: Department of Orthopaedic Surgery, University of California, 350 Dickinson St., San Diego, CA 92103, USA.
authors.forename: Eli Robert
authors.initials: ER
authors.lastname: Groppo
authors.forename: Robert Kenneth
authors.initials: RK
authors.lastname: Eastlack
authors.forename: Andrew
authors.initials: A
authors.lastname: Mahar
authors.forename: Alan Robert
authors.initials: AR
authors.lastname: Hargens
authors.forename: Robert Alan
authors.initials: RA
authors.lastname: Pedowitz
mesh_terms: D000328:Adult; D001835:Body Weight / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000378:metabolism*; D004576:Electromyography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D018471:Hypergravity; D008150:Lower Body Negative Pressure; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009142:Musculoskeletal Physiological Phenomena; D009141:Musculoskeletal System / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology; D012420:Running / Q000502:physiology*