title: Is muscle coordination affected by loading condition in ballistic movements?
abstract: This study aimed to investigate the effect of loading on lower limb muscle coordination involved during ballistic squat jumps. Twenty athletes performed ballistic squat jumps on a force platform. Vertical force, velocity, power and electromyographic (EMG) activity of lower limb muscles were recorded during the push-off phase and compared between seven loading conditions (0-60% of the concentric-only maximal repetition). The increase in external load increased vertical force (from 1962 N to 2559 N; P=0.0001), while movement velocity decreased (from 2.5 to 1.6 ms(-1); P=0.0001). EMG activity of tibialis anterior first peaked at 5% of the push-off phase, followed by gluteus maximus (35%), vastus lateralis and soleus (45%), rectus femoris (55%), gastrocnemius lateralis (65%) and semitendinosus (75%). This sequence of activation (P=0.67) and the amplitude of muscle activity (P=0.41) of each muscle were not affected by loading condition. However, a main effect of muscle was observed on these parameters (peak value: P<0.001; peak occurrence: P=0.02) illustrating the specific role of each muscle during the push-off phase. Our findings suggest that muscle coordination is not influenced by external load during a ballistic squat jump.
authors.affiliation: French National Institute of Sport (INSEP), Research Department, Laboratory Sport, Expertise and Performance, Paris, France; CETAPS UPRES EA 3832, Faculty of Sports Sciences, University of Rouen, Mont Saint Aignan Cedex, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Giroux
authors.affiliation: French National Institute of Sport (INSEP), Research Department, Laboratory Sport, Expertise and Performance, Paris, France.
authors.forename: Gaël
authors.initials: G
authors.lastname: Guilhem
authors.affiliation: French National Institute of Sport (INSEP), Research Department, Laboratory Sport, Expertise and Performance, Paris, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Couturier
authors.affiliation: CETAPS UPRES EA 3832, Faculty of Sports Sciences, University of Rouen, Mont Saint Aignan Cedex, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Chollet
authors.affiliation: French National Institute of Sport (INSEP), Research Department, Laboratory Sport, Expertise and Performance, Paris, France. Electronic address: giuseppe.rabita@insep.fr.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rabita
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D009068:Movement; D052580:Muscle Stretching Exercises; D018482:Muscle, Skeletal / Q000502:physiology*
keywords: EMG; Force platform; Force–velocity relationship; Squat jump