Abstract
Background of Study: The piggyback carry has recently become a more popular exercise through the emerging sport of CrossFit. Purpose: The purpose of this study was to determine any biomechanical differences that exist in the lumbar spine when carrying no load, a backpack, and a person on the back. Methods: Twelve 70+ kg male strength-trained athletes were recruited from local CrossFit affiliates. One child with a mass of 27 kg was recruited to be the piggybackpassenger for all participants. All participants and the guardian of the passenger signed an informed consent form. The participants walked three times over a force plate for each of three conditions: carrying no load, a 27 kg backpack, or a 27 kg passenger. Three Canon video cameras recorded each trial, and Dartfish Software was used to measure joint angles and gait parameters. Maximal trunk inclination angle, was used in a static lumbar spine model to calculate trunkmuscle torque and force, and lumbosacral joint reaction forces. Results: Both load conditions produced compensatory trunk flexion; trunk flexion increased from no load to piggybacking to backpacking. Mean values were determined for each participant for each variable, and these values were compared amongst the three conditions of no load, piggybacking, and backpacking. An alpha value of 0.05 was used. Conclusion: Due to the more extreme position of the trunk andgreater magnitude of torques, backpacking likely places the musculoskeletal system at more risk than does piggybacking.
Highlights
Carrying a load, and carrying a load posterior to the spine, has been identified as an activity that should be considered as a possible risk to the lumbar spine by lifting studies (Cholewicki, McGill, & Norman, 1991) and backpack studies (Chow et al, 2005; Goh, Thambyah, & Bose, 1998)
The purpose of this study was to determine any biomechanical differences that exist in the lumbar spine when carrying no load, a backpack, and a person on the back
A biomechanical model was devised which accepted as input the torques applied in the clockwise and counterclockwise directions about the L5/S1 axis, and used these values to determine the total torques acting in each condition, as well as the total compressive and shear forces acting on S1
Summary
Carrying a load posterior to the spine, has been identified as an activity that should be considered as a possible risk to the lumbar spine by lifting studies (Cholewicki, McGill, & Norman, 1991) and backpack studies (Chow et al, 2005; Goh, Thambyah, & Bose, 1998). The piggyback is an important part of family life and social culture, as a common bonding and rough-housing experience important to social and physical development within a family or friendship (Bennett, 1999), but it is used by athletes for strength training. The piggyback carry has recently become a more popular exercise through the emerging sport of CrossFit. Purpose: The purpose of this study was to determine any biomechanical differences that exist in the lumbar spine when carrying no load, a backpack, and a person on the back. The participants walked three times over a force plate for each of three conditions: carrying no load, a 27 kg backpack, or a 27 kg passenger. Conclusion: Due to the more extreme position of the trunk and greater magnitude of torques, backpacking likely places the musculoskeletal system at more risk than does piggybacking
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