Efficacy of 3 days/wk resistance training on myofiber hypertrophy and myogenic mechanisms in young vs. older adults

• Published in: Journal of applied physiology (1985) Vol. 101; no. 2; pp. 531 - 544
• Main Authors: Kosek, David J, Kim, Jeong-su, Petrella, John K, Cross, James M, Bamman, Marcas M
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.08.2006; American Physiological Society
• Subjects: Adult; Aged; Aging - physiology; Biological and medical sciences; Exercise; Exercise - physiology; Female; Fundamental and applied biological sciences. Psychology; Human subjects; Humans; Hypertrophy - pathology; Hypertrophy - physiopathology; Male; Middle Aged; Muscle Development - physiology; Muscular system; MyoD Protein - genetics; MyoD Protein - physiology; Myofibrils - pathology; Myofibrils - physiology; Myogenic Regulatory Factor 5 - genetics; Myogenic Regulatory Factor 5 - physiology; Myogenic Regulatory Factors - genetics; Myogenic Regulatory Factors - physiology; Myogenin - genetics; Myogenin - physiology; Older people; Physical training; RNA, Messenger - analysis; Sex Characteristics; Time Factors; Tissues; Weight Lifting; Human; myosin heavy chain; Vertebrata; Heavy peptide chain; Physical training; Mammalia; MyoD; myogenin; Myosin; Elderly; Hypertrophy; sarcopenia
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.01474.2005

Departments of 1 Physiology and Biophysics and 3 Surgery, University of Alabama at Birmingham, and 2 Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Birmingham, Alabama Submitted 22 November 2005 ; accepted in final form 4 April 2006 Resistance training (RT) has shown the most promise in reducing/reversing effects of sarcopenia, although the optimum regime specific for older adults remains unclear. We hypothesized myofiber hypertrophy resulting from frequent (3 days/wk, 16 wk) RT would be impaired in older (O; 60–75 yr; 12 women, 13 men), sarcopenic adults compared with young (Y; 20–35 yr; 11 women, 13 men) due to slowed repair/regeneration processes. Myofiber-type distribution and cross-sectional area (CSA) were determined at 0 and 16 wk. Transcript and protein levels of myogenic regulatory factors (MRFs) were assessed as markers of regeneration at 0 and 24 h postexercise, and after 16 wk. Only Y increased type I CSA 18% ( P < 0.001). O showed smaller type IIa (–16%) and type IIx (–24%) myofibers before training ( P < 0.05), with differences most notable in women. Both age groups increased type IIa (O, 16%; Y, 25%) and mean type II (O, 23%; Y, 32%) size ( P < 0.05). Growth was generally most favorable in young men. Percent change scores on fiber size revealed an age x gender interaction for type I fibers ( P < 0.05) as growth among Y (25%) exceeded that of O (4%) men. Myogenin and myogenic differentiation factor D (MyoD) mRNAs increased ( P < 0.05) in Y and O, whereas myogenic factor (myf)-5 mRNA increased in Y only ( P < 0.05). Myf-6 protein increased ( P < 0.05) in both Y and O. The results generally support our hypothesis as 3 days/wk training led to more robust hypertrophy in Y vs. O, particularly among men. However, this differential hypertrophy adaptation was not explained by age variation in MRF expression. sarcopenia; myogenin; MyoD; myosin heavy chain Address for reprint requests and other correspondence: M. M. Bamman, UAB Dept. of Physiology and Biophysics, Muscle Research Laboratory, GRECC/11G VA Medical Center, 1530 3rd Ave., South Birmingham, AL 35294-0001 (e-mail mbamman{at}uab.edu )