A description of shock attenuation for children running.
BACKGROUND
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.


METHODS
Prospective cohort study.


METHODS
Biomechanics laboratory.


METHODS
Eleven boys (age = 10.5 +/- 0.9 years, height = 143.7 +/- 8.3 cm, mass = 39.4 +/- 10.9 kg) and 7 girls (age = 9.9 +/- 1.1 years, height = 136.2 +/- 7.7 cm, mass = 35.1 +/- 9.6 kg) participated.


METHODS
Participants completed 4 running conditions, including 3 treadmill (TM) running speeds (preferred, fast [0.5 m/s more than preferred], and slow [0.5 m/s less than preferred]) and 1 overground (OG) running speed.


METHODS
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) = 4.80, P = .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) = 5.04, P = .04) and HdPk (F(1,16) = 6.04, P = .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 >or= .05). Shock attenuation (F(1,16) = 33.51, P < .001) and LgPk (F(1,16) = 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.
Mercer
John A
JA
Department of Kinesiology and Nutrition Sciences, University of Nevada, Las Vegas, Nevada 89195-3019, USA. john.mercer@unlv.edu
Dufek
Janet S
JS
Mangus
Brent C
BC
Rubley
Mack D
MD
Bhanot
Kunal
K
Aldridge
Jennifer M
JM
D000054:Acceleration; D000222:Adaptation, Physiological; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D002648:Child; D002669:Child Welfare; D005080:Exercise Test; D005260:Female; D006801:Humans; D007869:Leg Injuries / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012420:Running / Q000293:injuries* / Q000502:physiology; D012737:Sex Factors; D013223:Statistics as Topic; D014732:Vibration / Q000009:adverse effects*
Br J Sports Med. 2006 Sep;40(9):749-60
16807307
Med Sci Sports Exerc. 1992 Apr;24(4):462-6
1560744
Curr Opin Pediatr. 2002 Dec;14(6):719-22
12436044
Sports Med. 1989 Jan;7(1):32-41
2652244
Med Sci Sports Exerc. 2001 Oct;33(10):1701-7
11581555
Eur J Appl Physiol. 2002 Aug;87(4-5):403-8
12172880
J Sports Med Phys Fitness. 1996 Mar;36(1):43-8
8699837
Br J Sports Med. 2004 Apr;38(2):168-72
15039253
J Appl Biomech. 1998 Aug;14(3):300-311
28121250
Curr Opin Pediatr. 1999 Feb;11(1):84-8
10084091
J Pediatr Orthop. 2004 Nov-Dec;24(6):623-8
15502559
Med Sci Sports Exerc. 2000 Sep;32(9):1635-41
10994917
Med Sci Sports Exerc. 2003 Feb;35(2):307-13
12569221
Am J Sports Med. 1978 Mar-Apr;6(2):40-50
25589
J Sport Rehabil. 2008 Aug;17(3):230-42
18708677
J Sports Med. 1974 Jul-Aug;2(4):189-98
4468337
Sports Med. 2007;37(4-5):299-301
17465593
J Physiol. 1998 Jun 15;509 ( Pt 3):927-40
9596810
J Sports Sci. 2003 Nov;21(11):911-9
14626370
Med Sci Sports Exerc. 1998 Jan;30(1):128-35
9475654
J Electromyogr Kinesiol. 2001 Aug;11(4):263-8
11532597
Med Sci Sports Exerc. 2003 Oct;35(10):1745-50
14523314