title: Region specific patellar tendon hypertrophy in humans following resistance training.
abstract: OBJECTIVE
  To examine if cross-sectional area (CSA) differs along the length of the human patellar tendon (PT), and if there is PT hypertrophy in response to resistance training.
  
  
  METHODS
  Twelve healthy young men underwent baseline and post-training assessments. Maximal isometric knee extension strength (MVC) was determined unilaterally in both legs. PT CSA was measured at the proximal-, mid- and distal PT level and quadriceps muscle CSA was measured at mid-thigh level using magnetic resonance imaging. Mechanical properties of the patellar tendons were determined using ultrasonography. Subsequently, subjects performed 12 weeks of heavy resistance knee extension training with one leg (Heavy-leg), and light resistance knee extension training with the other leg (Light-leg).
  
  
  RESULTS
  The MVC increased for heavy-leg (15 +/- 4%, P < 0.05), but not for light-leg (6 +/- 4%). Quadriceps CSA increased in heavy-legs (6 +/- 1%, P < 0.05) while unchanged in light-legs. Proximal PT CSA (104 +/- 4 mm(2)) was smaller than the mid-tendon CSA (118 +/- 3 mm(2)), which again was smaller than distal tendon CSA (127 +/- 2 mm(2), P < 0.05). Light-leg PT CSA increased by 7 +/- 3% (P < 0.05) at the proximal tendon level, but was otherwise unchanged. Heavy-leg PT CSA increased at the proximal and distal tendon levels by 6 +/- 3% and 4 +/- 2% respectively (P < 0.05), but was unchanged at the mid tendon level. PT stiffness increased in heavy-legs (P < 0.05) but was unchanged in light-legs. Modulus remained unchanged in both legs.
  
  
  CONCLUSIONS
  To our knowledge, this study is the first to report tendon hypertrophy following resistance training. Further, the data show that the human PT CSA varies along the length of the tendon.
authors.affiliation: Institute of Sports Medicine Copenhagen, Bispebjerg Hospital, Copenhagen, Denmark. mads.kongsgaard@get2net.dk
authors.forename: M
authors.initials: M
authors.lastname: Kongsgaard
authors.forename: S
authors.initials: S
authors.lastname: Reitelseder
authors.forename: T G
authors.initials: TG
authors.lastname: Pedersen
authors.forename: L
authors.initials: L
authors.lastname: Holm
authors.forename: P
authors.initials: P
authors.lastname: Aagaard
authors.forename: M
authors.initials: M
authors.lastname: Kjaer
authors.forename: S P
authors.initials: SP
authors.lastname: Magnusson
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D006801:Humans; D006984:Hypertrophy; D007866:Leg; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology; D017847:Patellar Ligament / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D010806:Physical Education and Training; D005082:Physical Exertion / Q000502:physiology; D018709:Statistics, Nonparametric; D013997:Time Factors; D014463:Ultrasonography