A Description of Shock Attenuation for Children Running

Abstract

Vegas. Dr Mangus is now at Texas A&M University-Commerce.Context: A growing number of children are participating in organized sport activities, resulting in a concomitant increase in lower extremity injuries. Little is known about the impact generated when children are running or how this impact is attenuated in child runners.Objective: To describe shock attenuation characteristics for children running at different speeds on a treadmill and at a single speed over ground.Design: Prospective cohort study. Setting: Biomechanics laboratory.Patients or Other Participants: Eleven boys (age 5 10.5 6 0.9 years, height 5 143.7 6 8.3 cm, mass 5 39.4 6 10.9 kg) and 7 girls (age 5 9.9 6 1.1 years, height 5 136.2 6 7.7 cm, mass 5 35.1 6 9.6 kg) participated.Intervention ( Main Outcome Measure(s): We measured leg peak impact acceleration (LgPk), head peak impact acceleration (HdPk), and shock attenuation (ratio of LgPk to HdPk).Results: Shock attenuation (F 2,16 5 4.80, P 5 .01) was influenced by the interaction of speed and sex. Shock attenuation increased across speeds (slow, preferred, fast) for boys (P , .05) but not for girls (P . .05). Both LgPk (F 1,16 5 5.04, P 5 .04) and HdPk (F 1,16 5 6.04, P 5 .03) were different across speeds, and both were greater for girls than for boys. None of the dependent variables were influenced by the interaction of setting (TM, OG) and sex (P $ .05). Shock attenuation (F 1,16 5 33.51, P , .001) and LgPk (F 1,16 5 31.54, P , .001) were different between TM and OG, and each was greater when running OG than on the TM, regardless of sex.Conclusions: Shock attenuation was between 66% and 76% for children running under a variety of conditions. Girls had greater peak impact accelerations at the leg and head levels than boys but achieved similar shock attenuation. We do not know how these shock attenuation characteristics are related to overuse injuries.Key Words: boy and girl runners, impact, lower extremity injuries Key Points N Children attenuated different amounts of shock while running on a treadmill and over ground. N Leg and head peak impact accelerations were greater in girls than in boys. N Boys and girls achieved similar shock attenuation levels under various running conditions. N We do not know the mechanism for shock attenuation in child runners. N When developing rehabilitation programs for children, the practitioner should consider that shock attenuation varies across running speeds and between treadmill and overground running.

Effects of Foot Strike on Low Back Posture, Shock Attenuation, and Comfort in Running

“…For each stride, the peak left leg and head acceleration values were obtained and used to calculate shock attenuation using the following formula: [1 -(head peak / leg peak)] x 100 (26). Thus, a larger value was indicative of greater impact attenuation (25). For each foot strike pattem, the average shock attenuation of the 15 strides per subject was calculated and evaluated statistically (Fig.…”

“…Shock attenuation, the dissipation ofthe impact that occurs during initial contact of foot with the ground, is dependent on passive structures of the body and active movement. It can be influenced by running speed, stride length, and state of fatigue (25). If shock attenuation could change by running a different way, then perhaps injiuy and pain in the low back could change as well.…”

The Reporting of the Journalists of “Raz, Dwa, Trzy” at the Olympic Games in Berlin in 1936

“…Shock attenuation represents the mechanical process by which transient energy diminishes as it propagates through the musculoskeletal system (Valiant, 1990). Shock attenuation is achieved via muscle contraction, lower body alignment and passive musculoskeletal tissue deformation (Mercer et al, 2010). A further discrepancy is that Dufek et al (2009) quantified transient attenuation from the tibia to the head as opposed to the sacrum.…”

“…Shock attenuation is therefore an essential parameter when quantifying impact transients during running, as it serves a quantifiable indicator of the extent to which the impact shock wave is reduced (Shorten, Winslow, 1992). The mechanical process by which shock is attenuated is through the absorption of energy via muscle contraction, lower extremity alignment and deformation of passive musculoskeletal structures (Mercer et al, 2010). It has been shown that can be mediated by a number of different biomechanical/ anthropometrical parameters (Mercer et al, 2010).…”

“…The mechanical process by which shock is attenuated is through the absorption of energy via muscle contraction, lower extremity alignment and deformation of passive musculoskeletal structures (Mercer et al, 2010). It has been shown that can be mediated by a number of different biomechanical/ anthropometrical parameters (Mercer et al, 2010). However there is current no research which has examined sex differences in shock attenuation during running.…”