title: Assessment of the in-season changes in mechanical and neuromuscular characteristics in professional soccer players.
abstract: BACKGROUND
  The aim of this study was to monitor in-season changes in the mechanical and neuromuscular characteristics of knee extensor and flexor muscles in professional soccer players.
  
  
  METHODS
  Twenty-one professional soccer players (soccer group, or SG) and sixteen non-soccer playing males (non-soccer group, or NSG) were assessed by tensiomyography on two occasions: just after the start of the competitive season and 10 weeks later. During this time the soccer players' training sessions were built mainly on speed and strength drills. Mixed-design factorial analysis of variance was conducted and effect sizes were calculated.
  
  
  RESULTS
  There was a significant interaction between time (assessment points) x group (SG vs. NSG) x muscle for contraction time (Tc), maximum radial muscle displacement (Dm), and delay time (Td). In the case of the knee extensors, after 10 weeks, there was a 17.7%-22.7% decrease in Tc, an 8.7%-9.9% decrease in Td, and a 12.2%-14.2% decrease in Dm knee extensor in the SG (P<0.01), with a large effect size. In the case of the knee flexors, by contrast, there was an 11.9% increase in Td and a 24.5% increase in Dm (P<0.01), with a moderate to large effect size. The findings confirm that mechanical and neuromuscular characteristics change over time and also vary according to the characteristics of the athlete (SG vs. NSG) and the muscle analyzed.
  
  
  CONCLUSIONS
  In conclusion, soccer coaches could use Tc, Td, and Dm data to individualize work load and intensity and control the effects of neuromuscular training throughout the season using a portable, non-invasive technique that, unlike stress tests, does not cause fatigue and therefore does not interfere with training periodization.
authors.affiliation: Faculty of Education and Sport Sciences, University of Vigo, Pontevedra, Spain - oscargarcia@uvigo.es.
authors.forename: Oscar
authors.initials: O
authors.lastname: García-García
authors.forename: Virginia
authors.initials: V
authors.lastname: Serrano-Gómez
authors.forename: Antonio
authors.initials: A
authors.lastname: Hernández-Mendo
authors.forename: Antonio
authors.initials: A
authors.lastname: Tapia-Flores
mesh_terms: D000328:Adult; D056352:Athletes; D003430:Cross-Sectional Studies; D005080:Exercise Test; D006801:Humans; D007717:Knee / Q000502:physiology; D007719:Knee Joint; D008137:Longitudinal Studies; D008297:Male; D008991:Monitoring, Physiologic; D053580:Muscle Strength; D011597:Psychomotor Performance / Q000502:physiology*; D012916:Soccer / Q000502:physiology; D055815:Young Adult