Kathryn L Havens1, Anna C Severin2, David B Bumpass3, Erin M Mannen4. 1. Division of Biokinesiology and Physical Therapy, University of Southern California, 1540 East Alcazar Street, CHP-155, Los Angeles, CA 90033, United States. Electronic address: khavens@usc.edu. 2. Department of Orthopaedic Surgery, University of Arkansas for Medical Sciences, 4301 West Markham Street, Slot 531, Little Rock, AR 72205, United States. Electronic address: aseverin@uams.edu. 3. Department of Orthopaedic Surgery, University of Arkansas for Medical Sciences, 4301 West Markham Street, Slot 531, Little Rock, AR 72205, United States. Electronic address: erinmannen@boisestate.edu. 4. Department of Orthopaedic Surgery, University of Arkansas for Medical Sciences, 4301 West Markham Street, Slot 531, Little Rock, AR 72205, United States; Center for Orthopaedic Biomechanics, Department of Mechanical and Materials Engineering, University of Denver, 2115 East Wesley Avenue, Denver, CO 80208, United States. Electronic address: emannen@uams.edu.
Abstract
BACKGROUND: Human babies are carried by their caregivers during infancy, and the use of ergonomic aids to wear the baby on the body has recently grown in popularity. However, the effects of wearing or holding a baby in-arms on an individual's mechanics during gait and a common object retrieval task are not fully understood. RESEARCH QUESTION: What are the differences in: 1) spatiotemporal, lower extremity kinematics, and ground reaction force variables during gait, and 2) technique, center of mass motion, and kinematics during an object retrieval task between holding and wearing an infant mannequin? METHODS: In this prospective biomechanics study, 10 healthy females performed over-ground walking and an object retrieval task in three conditions, holding: (1) nothing (unloaded), (2) an infant mannequin in-arms, and (3) an infant mannequin in a baby carrier. Mechanics were compared using repeated measures ANOVA. RESULTS: During gait, greater vertical ground reaction force and impulse and braking force was found during the in-arms and carrier conditions compared to unloaded. Significant but small (<5°) differences were found between conditions in lower extremity kinematics. Increased back extension was found during carrier and in-arms compared to unloaded. Step length was the only spatiotemporal parameter that differed between conditions. During object retrieval, most participants used a squatting technique to retrieve the object from the floor. They maintained a more upright posture, with less trunk flexion and anteroposterior movement of their center of mass, and also did not try to fold forward over their hips during the two loaded conditions. Lower extremity kinematics did not differ between unloaded and carrier, suggesting that babywearing may promote more similar lower extremity mechanics to not carrying anything. SIGNIFICANCE: Holding or wearing an infant provides a mechanical constraint that impacts the forces and kinematics, which has implications for caregivers' pain and dysfunction.
BACKGROUND: Human babies are carried by their caregivers during infancy, and the use of ergonomic aids to wear the baby on the body has recently grown in popularity. However, the effects of wearing or holding a baby in-arms on an individual's mechanics during gait and a common object retrieval task are not fully understood. RESEARCH QUESTION: What are the differences in: 1) spatiotemporal, lower extremity kinematics, and ground reaction force variables during gait, and 2) technique, center of mass motion, and kinematics during an object retrieval task between holding and wearing an infant mannequin? METHODS: In this prospective biomechanics study, 10 healthy females performed over-ground walking and an object retrieval task in three conditions, holding: (1) nothing (unloaded), (2) an infant mannequin in-arms, and (3) an infant mannequin in a baby carrier. Mechanics were compared using repeated measures ANOVA. RESULTS: During gait, greater vertical ground reaction force and impulse and braking force was found during the in-arms and carrier conditions compared to unloaded. Significant but small (<5°) differences were found between conditions in lower extremity kinematics. Increased back extension was found during carrier and in-arms compared to unloaded. Step length was the only spatiotemporal parameter that differed between conditions. During object retrieval, most participants used a squatting technique to retrieve the object from the floor. They maintained a more upright posture, with less trunk flexion and anteroposterior movement of their center of mass, and also did not try to fold forward over their hips during the two loaded conditions. Lower extremity kinematics did not differ between unloaded and carrier, suggesting that babywearing may promote more similar lower extremity mechanics to not carrying anything. SIGNIFICANCE: Holding or wearing an infant provides a mechanical constraint that impacts the forces and kinematics, which has implications for caregivers' pain and dysfunction.
Authors: Ge Wu; Sorin Siegler; Paul Allard; Chris Kirtley; Alberto Leardini; Dieter Rosenbaum; Mike Whittle; Darryl D D'Lima; Luca Cristofolini; Hartmut Witte; Oskar Schmid; Ian Stokes Journal: J Biomech Date: 2002-04 Impact factor: 2.712