title: The Effect of Body Mass on Eccentric Knee-Flexor Strength Assessed With an Instrumented Nordic Hamstring Device (Nordbord) in Football Players.
abstract: OBJECTIVE
  To examine the effect of body mass (BM) on eccentric knee-flexor strength using the Nordbord and offer simple guidelines to control for the effect of BM on knee-flexor strength.
  
  
  METHODS
  Data from 81 soccer players (U17, U19, U21, senior 4th French division, and professionals) and 41 Australian Football League (AFL) players were used for analysis. They all performed 1 set of 3 maximal repetitions of the bilateral Nordic hamstring exercise, with the greatest strength measure used for analysis. The main regression equation obtained from the overall sample was used to predict eccentric knee-flexor strength from a given BM (moderate TEE, 22%). Individual deviations from the BM-predicted score were used as a BM-free index of eccentric knee- flexor strength.
  
  
  RESULTS
  There was a large (r = .55, 90% confidence limits .42;.64) correlation between eccentric knee-flexor strength and BM. Heavier and older players (professionals, 4th French division, and AFL) outperformed their lighter and younger (U17-U21) counterparts, with the soccer professionals presenting the highest absolute strength. Professional soccer players were the only ones to show strength values likely slightly greater than those expected for their BM.
  
  
  CONCLUSIONS
  Eccentric knee-flexor strength, as assessed with the Nordbord, is largely BM-dependent. To control for this effect, practitioners may compare actual test performances with the expected strength for a given BM, using the following predictive equation: Eccentric strength (N) = 4 × BM (kg) + 26.1. Professional soccer players with specific knee-flexor-training history and enhanced neuromuscular performance may show higher than expected values.
authors.forename: Martin
authors.initials: M
authors.lastname: Buchheit
authors.forename: Yannick
authors.initials: Y
authors.lastname: Cholley
authors.forename: Mark
authors.initials: M
authors.lastname: Nagel
authors.forename: Nicholas
authors.initials: N
authors.lastname: Poulos
mesh_terms: D000328:Adult; D056352:Athletes; D001265:Athletic Injuries / Q000503:physiopathology / Q000517:prevention & control*; D015992:Body Mass Index; D005080:Exercise Test; D005538:Football / Q000293:injuries / Q000502:physiology*; D000070633:Hamstring Muscles / Q000293:injuries*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D012307:Risk Factors; D055815:Young Adult
keywords: Australian Football League; association football; hamstring strength; injuries; soccer