title: Maximal but not submaximal performance is reduced by constant-speed 10-km run.
abstract: OBJECTIVE
  Effects of endurance exercise on running economy, mechanics, force generating capacity and their interactions were examined. During the exercise, metabolic, kinetic and kinematic variables were recorded to find out adaptive mechanisms in the course of the fatiguing run. In addition, before and after it maximal force and power production was tested.
  
  
  METHODS
  
  
  
  METHODS
  comparative.
  
  
  METHODS
  University.
  
  
  METHODS
  7 men unaccustomed to endurance training run 10 km at individually chosen constant speed (3.5+/-0.5 m x s(-1)) on an indoor track.
  
  
  METHODS
  3-D ground reaction forces, electromyographic (EMG) activities from 7 leg muscles, pulmonary ventilation, gas exchange, heart rate and movement kinematics were measured during the run. Blood lactate and serum creatine kinase activity were determined. Maximal voluntary contraction (MVC) with superimposed double twitch (DT), and passive DT tests in plantarflexor muscles were performed before and after the 10 km run. Changes in 20 m sprint performance were evaluated in before-after comparison.
  
  
  RESULTS
  The 10 km run caused significant reductions in maximal running speed (8.2 vs 7.6 m x s(-1), p<0.05), in MVC (1216 vs. 984 N, p<0.05), and in passive DT (271 vs 211 N, p<0.05). During the submaximal run, however, the subjects were able to maintain relatively constant oxygen consumption and running kinematics. Greatest changes in EMG activity and kinetics were seen during the first 2 km.
  
  
  CONCLUSIONS
  After initial adjustment, the runners are able to maintain submaximal running speed with very little changes in running economy, kinetics and kinematics. However, fatigue-induced impairment in the force generating capacity of the contractile component can be revealed by tests measuring maximum performance.
authors.affiliation: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyvlskyll, Jyvlskyll, Finland. finni@sport.jyu.fi
authors.forename: T
authors.initials: T
authors.lastname: Finni
authors.forename: H
authors.initials: H
authors.lastname: Kyröläinen
authors.forename: J
authors.initials: J
authors.lastname: Avela
authors.forename: P V
authors.initials: PV
authors.lastname: Komi
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*