Training-induced changes in structural and mechanical properties of the patellar tendon are related to muscle hypertrophy but not to strength gains

• Published in: Journal of applied physiology (1985) Vol. 107; no. 2; pp. 523 - 530
• Main Authors: Seynnes, O. R, Erskine, R. M, Maganaris, C. N, Longo, S, Simoneau, E. M, Grosset, J. F, Narici, M. V
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.08.2009; American Physiological Society
• Subjects: Adaptation, Physiological; Adolescent; Biological and medical sciences; Biomechanical Phenomena; Correlation analysis; Elastic Modulus; Electromyography; Fundamental and applied biological sciences. Psychology; Humans; Hypertrophy; Isometric Contraction; Magnetic Resonance Imaging; Male; Mechanical properties; Muscle Strength; Muscle Strength Dynamometer; Muscles; Muscular system; NMR; Nuclear magnetic resonance; Patellar Ligament - diagnostic imaging; Patellar Ligament - pathology; Patellar Ligament - physiopathology; Physical training; Quadriceps Muscle - pathology; Quadriceps Muscle - physiopathology; Resistance Training; Tendons; Time Factors; Torque; Ultrasonography; Young Adult; Connective tissue; Vertebrata; overloading; Physical training; Muscle strength; Mammalia; Collagen; Glycoprotein; Mechanical properties; Hypertrophy; Tendon
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00213.2009

1 Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, United Kingdom; 2 Laboratoire d'Automatique, de Mécanique et d'Informatique industrielles et Humaines, Université de Valenciennes et du Hainaut-Cambrésis, Valenciennes, France; and 3 Laboratoire de Biomécanique, Equipe Biomécanique, Sport et Santé, Université Paris 13-Arts et Métiers ParisTech CNRS UMR, Bobigny, France Submitted 25 February 2009 ; accepted in final form 26 May 2009 To obtain a better understanding of the adaptations of human tendon to chronic overloading, we examined the relationships between these adaptations and the changes in muscle structure and function. Fifteen healthy male subjects (20 ± 2 yr) underwent 9 wk of knee extension resistance training. Patellar tendon stiffness and modulus were assessed with ultrasonography, and cross-sectional area (CSA) was determined along the entire length of the tendon by using magnetic resonance imaging. In the quadriceps muscles, architecture and volume measurements were combined to obtain physiological CSA (PCSA), and maximal isometric force was recorded. Following training, muscle force and PCSA increased by 31% ( P < 0.0001) and 7% ( P < 0.01), respectively. Tendon CSA increased regionally at 20–30%, 60%, and 90–100% of tendon length (5–6%; P < 0.05), and tendon stiffness and modulus increased by 24% ( P < 0.001) and 20% ( P < 0.01), respectively. Although none of the tendon adaptations were related to strength gains, we observed a positive correlation between the increase in quadriceps PCSA and the increases in tendon stiffness ( r = 0.68; P < 0.01) and modulus ( r = 0.75; P < 0.01). Unexpectedly, the increase in muscle PCSA was inversely related to the distal and the mean increases in tendon CSA (in both cases, r = –0.64; P < 0.05). These data suggest that, following short-term resistance training, changes in tendon mechanical and material properties are more closely related to the overall loading history and that tendon hypertrophy is driven by other mechanisms than those eliciting tendon stiffening. overloading; connective tissue; collagen Address for reprint requests and other correspondence: O. R. Seynnes, Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan Univ., John Dalton Bldg. (E310), Oxford Rd., Manchester, M1 5GD, United Kingdom (e-mail: o.seynnes{at}mmu.ac.uk )