title: Muscle fiber type, Achilles tendon length, potentiation, and running economy.
abstract: The purpose of this investigation was to develop a potential model for how muscle fiber type, Achilles tendon length, stretch-shortening cycle potentiation (SSCP), and leg strength interact with running economy. Twenty trained male distance runners 24-40 years of age served as subjects. Running economy (net oxygen uptake) was measured while running on a treadmill. Leg press SSCP(force) and SSCP(velocity) were determined by measuring the difference in velocity between a static leg press throw and a countermovement leg press throw. Vertical jump SSCP was determined by measuring the difference in jump height between a static jump and a drop jump from a 20.3-cm bench. Tendon length was measured by magnetic resonance imaging, and muscle fiber type was made from a vastus lateralis muscle biopsy. Type IIx muscle fiber percent (r = 0.70, p < 0.001) and leg strength (r = 0.95, p < 0.001) were positively and independently related to late eccentric force development. Achilles tendon length (r = 0.42, p ≤ 0.05) and late eccentric force during stretch-shortening cycle (r = 0.76, p < 0.001) were independently related to SSCP(force). SSCP(force) was related to SSCP(velocity), which in turn was related to running economy (r = 0.61, p < 0.01). These results suggest that longer Achilles tendon length, type II fiber, and muscular leg strength may enhance the potential for SSCP, running economy, and physiological effort while running.
authors.affiliation: 1Department of Human Studies; 2Department of Physical Therapy; 3Department of Physiology and Biophysics; 4Department of Nuclear Medicine Technology Program, University of Alabama at Birmingham, Birmingham, Alabama; 5Physical Therapy Program, Carroll University, Wauksha, WI; and 6Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Canada.
authors.forename: Gary R
authors.initials: GR
authors.lastname: Hunter
authors.forename: John P
authors.initials: JP
authors.lastname: McCarthy
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Carter
authors.forename: Marcas M
authors.initials: MM
authors.lastname: Bamman
authors.forename: Emily S
authors.initials: ES
authors.lastname: Gaddy
authors.forename: Gordon
authors.initials: G
authors.lastname: Fisher
authors.forename: Kostantina
authors.initials: K
authors.lastname: Katsoulis
authors.forename: Eric P
authors.initials: EP
authors.lastname: Plaisance
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Newcomer
mesh_terms: D000125:Achilles Tendon / Q000033:anatomy & histology* / Q000502:physiology*; D000328:Adult; D005080:Exercise Test; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D052097:Quadriceps Muscle / Q000166:cytology* / Q000502:physiology*; D012420:Running / Q000502:physiology*; D014891:Weight Lifting / Q000502:physiology; D055815:Young Adult