title: Impact reduction during running: efficiency of simple acute interventions in recreational runners.
abstract: Running-related stress fractures have been associated with the overall impact intensity, which has recently been described through the loading rate (LR). Our purpose was to evaluate the effects of four acute interventions with specific focus on LR: wearing racing shoes (RACE), increasing step frequency by 10 % (FREQ), adopting a midfoot strike pattern (MIDFOOT) and combining these three interventions (COMBI). Nine rearfoot-strike subjects performed five 5-min trials during which running kinetics, kinematics and spring-mass behavior were measured for ten consecutive steps on an instrumented treadmill. Electromyographic activity of gastrocnemius lateralis, tibialis anterior, biceps femoris and vastus lateralis muscles was quantified over different phases of the stride cycle. LR was significantly and similarly reduced in MIDFOOT (37.4 ± 7.20 BW s(-1), -56.9 ± 50.0 %) and COMBI (36.8 ± 7.15 BW s(-1), -55.6 ± 29.2 %) conditions compared to NORM (56.3 ± 11.5 BW s(-1), both P < 0.001). RACE (51.1 ± 9.81 BW s(-1)) and FREQ (52.7 ± 11.0 BW s(-1)) conditions had no significant effects on LR. Running with a midfoot strike pattern resulted in a significant increase in gastrocnemius lateralis pre-activation (208 ± 97.4 %, P < 0.05) and in a significant decrease in tibialis anterior EMG activity (56.2 ± 15.5 %, P < 0.05) averaged over the entire stride cycle. The acute attenuation of foot-ground impact seems to be mostly related to the use of a midfoot strike pattern and to a higher pre-activation of the gastrocnemius lateralis. Further studies are needed to test these results in prolonged running exercises and in the long term.
authors.affiliation: University of Lyon, 42023 Saint-Etienne, France.
authors.forename: Marlène
authors.initials: M
authors.lastname: Giandolini
authors.forename: Pierrick J
authors.initials: PJ
authors.lastname: Arnal
authors.forename: Guillaume Y
authors.initials: GY
authors.lastname: Millet
authors.forename: Nicolas
authors.initials: N
authors.lastname: Peyrot
authors.forename: Pierre
authors.initials: P
authors.lastname: Samozino
authors.forename: Blaise
authors.initials: B
authors.lastname: Dubois
authors.forename: Jean-Benoît
authors.initials: JB
authors.lastname: Morin
mesh_terms: D000293:Adolescent; D000328:Adult; D001265:Athletic Injuries / Q000517:prevention & control*; D001696:Biomechanical Phenomena; D001842:Bone and Bones / Q000293:injuries; D004576:Electromyography; D005080:Exercise Test; D005260:Female; D006801:Humans; D007596:Joints / Q000293:injuries / Q000502:physiology; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000293:injuries / Q000502:physiology; D011998:Recreation / Q000502:physiology; D040242:Risk Reduction Behavior; D012420:Running / Q000502:physiology*; D016896:Treatment Outcome; D055815:Young Adult