title: Effect of frequency on human unipedal hopping.
abstract: All mature forms of locomotion involve periods of unilateral stance. Unipedal hopping may provide useful information about the neuromuscular and biomechanical capabilities of a single lower extremity in adults. This study investigated whether hopping influenced vertical stiffness and lower extremity angular kinematics during human unipedal hopping. Vertical force and two-dimensional kinematics were measured in 10 healthy males hopping at three frequencies: preferred, +20%, and -20%. At +20%, compared to preferred, vertical stiffness increased 55% as hip flexion, knee flexion, and ankle dorsiflexion decreased, while at -20% vertical stiffness decreased 39.4% as hip flexion, knee flexion, and ankle dorsiflexion increased. As in bipedal hopping, the force-displacement relationship was more springlike at the preferred rate and +20% than at -20%. Given the prevalence of unilateral stance during walking, running, and skipping, findings related to unipedal hopping may be useful in the rehabilitation or conditioning of lower extremities.
authors.affiliation: Department of Physical Therapy and Human Movement Science, Sacred Heart University, Fairfield, CT 06432, USA. austing@sacredheart.edu
authors.forename: Gary P
authors.initials: GP
authors.lastname: Austin
authors.forename: David
authors.initials: D
authors.lastname: Tiberio
authors.forename: Gladys E
authors.initials: GE
authors.lastname: Garrett
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007596:Joints / Q000294:innervation / Q000502:physiology; D007866:Leg / Q000294:innervation*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation*; D009469:Neuromuscular Junction / Q000502:physiology; D010809:Physical Fitness; D011930:Reaction Time / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*