The effectiveness of stretch-shortening cycling in upper-limb extensor muscles during elite cross-country skiing with the double-poling technique.
This investigation was designed to evaluate the effectiveness of stretch-shortening cycling (SSC(EFF)) in upper-limb extensor muscles while cross-country skiing using the double-poling technique (DP). To this end, SSC(EFF) was analyzed in relation to DP velocity and performance. Eleven elite cross-country skiers performed an incremental test to determine maximal DP velocity (V(max)). Thereafter, cycle characteristics, elbow joint kinematics and poling forces were monitored on a treadmill while skiing at two sub-maximal and racing velocity (85% of V(max)). The average EMG activities of the triceps brachii and latissimus dorsi muscles were determined during the flexion and extension sub-phases of the poling cycle (EMG(FLEX), EMG(EXT)), as well as prior to pole plant (EMG(PRE)). SSC(EFF) was defined as the ratio of aEMG(FLEX) to aEMG(EXT). EMG(PRE) and EMG(FLEX) increased with velocity for both muscles (P < 0.01), as did SSC(EFF) (from 0.9 ± 0.3 to 1.3 ± 0.5 for the triceps brachii and from 0.9 ± 0.4 to 1.5 ± 0.5 for the latissimus dorsi) and poling force (from 253 ± 33 to 290 ± 36N; P < 0.05). Furthermore, SSC(EFF) was positively correlated to Vmax, to EMG(PRE) and EMG(FLEX) (P < 0.05). The neuromuscular adaptations made at higher velocities, when more poling force must be applied to the ground, exert a major influence on the DP performance of elite cross-country skiers.
CeRiSM (Research Center Sport Mountain & Health), Rovereto, Italy; Neurological and Movement Science Department, University of Verona, Italy. Electronic address: chiara.zoppirolli@univr.it.
Chiara
C
Zoppirolli
Hans-Christer
HC
Holmberg
Barbara
B
Pellegrini
Diego
D
Quaglia
Lorenzo
L
Bortolan
Federico
F
Schena
D000328:Adult; D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D004551:Elbow Joint / Q000502:physiology; D004576:Electromyography; D005080:Exercise Test; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular; D012865:Skiing / Q000502:physiology*; D064171:Superficial Back Muscles / Q000502:physiology; D055815:Young Adult
EMG; Effectiveness; Elbow joint; Performance; Pre-activation; Stretch shortening cycle