Metabolic demand and muscle damage induced by eccentric cycling of knee extensor and flexor muscles.
The aim of this study was to examine the metabolic demand and extent of muscle damage of eccentric cycling targeting knee flexor (FLEX) and knee extensor (EXT) muscles.


METHODS
Eight sedentary men (23.3 ± 0.7 y) underwent two eccentric cycling sessions (EXT and FLEX) of 30 min each, at 60% of the maximum power output. Oxygen consumption (VO2), heart rate (HR) and rated perceived exertion (RPE) were measured during cycling. Countermovement and squat jumps (CMJ and SJ), muscle flexibility, muscle soreness and pain pressure threshold (PPT) of knee extensor and flexor muscles were measured before, immediately after and 1-4 days after cycling.


RESULTS
FLEX showed greater VO2(+23%), HR (+14%) and RPE (+18%) than EXT. CMJ and SJ performance decreased similarly after cycling. Muscle soreness increased more after EXT than FLEX and PPT decreased in knee extensor muscles after EXT and decreased in knee flexor muscles after FLEX. Greater loss of muscle flexibility in knee flexor muscles after FLEX was observed.


CONCLUSIONS
Eccentric cycling of knee flexor muscles is metabolically more demanding than that of knee extensors, however muscle damage induced is similar. Knee flexors experienced greater loss of muscle flexibility possibly due to increased muscle stiffness following eccentric contractions.
a Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine , Universidad Finis Terrae , Santiago , Chile.
Luis
L
Peñailillo
a Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine , Universidad Finis Terrae , Santiago , Chile.
Nicolás
N
Guzmán
a Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine , Universidad Finis Terrae , Santiago , Chile.
José
J
Cangas
b Carrera de Kinesiología, Unidad Docente Asociada de Ciencias de la Salud, Facultad de Medicina , Pontificia Universidad Católica de Chile , Santiago , Chile.
Alvaro
A
Reyes
a Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine , Universidad Finis Terrae , Santiago , Chile.
Hermann
H
Zbinden-Foncea
D000328:Adult; D001265:Athletic Injuries / Q000503:physiopathology*; D001642:Bicycling / Q000502:physiology*; D006801:Humans; D007717:Knee / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries* / Q000503:physiopathology*; D011897:Random Allocation; D016059:Range of Motion, Articular / Q000502:physiology*; D055815:Young Adult
Exercise-induced muscle damage; hamstrings; muscle injury