ORIGINAL ARTICLE Matthew J. Sharman á Robert U. Newton Travis Triplett-McBride á Michael R. M. McGuigan Jerey M. McBride á Arja HaÈkkinen Keijo HaÈkkinen á William J. Kraemer Changes in myosin heavy chain composition with heavy resistance training in 60- to 75-year-old men and women Accepted: 25 September 2000 Abstract The purpose of this investigation was to assess the myosin heavy chain MHC) expression in the vastus lateralis muscle from elderly men and women, and to determine whether heavy resistance training in¯uences its expression. Twenty healthy, mildly physically active subjects gave their informed consent to participate in the study. The experimental group consisted of seven men and seven women [mean SD) age 65.5 4.1) years] and the control group consisted of three men and three women [mean SD) age 62.3 3.6) years]. The 6-month resistance training program was divided into two phases with weeks 1±12 consisting of high-intensity resistance training, and weeks 13±24 involving power training. Muscle biopsy samples were taken from the vastus lat- eralis muscle at week 0 and week 24 using the needle biopsy technique. The male and female experimental groups both exhibited a signi®cant decrease P £ 0.05) in the percentage of MHC IIb, while the experimental female group also demonstrated a signi®cant increase P £ 0.05) in the expression of MHC IIa, after 24 weeks of heavy resistance training. There was no change in MHC expression within the control group. The male [130.4 25.3) kg vs 171.1 30.5) kg] and female [58.2 8.3) kg vs 77.9 11.1) kg] experimental groups exhibited a signi®cant increase P £ 0.05) in the maximal strength values for the 1 repetition maximum 1RM) squat ex- ercise. The control group showed no change in strength for the 1RM squat exercise for either the male [115.8 35.10 kg vs 123.8 47.2) kg] or female [57.5 99.0) kg vs 58.3 2.9) kg] groups. The results clearly show that elderly subjects undergoing heavy resistance training have the ability to produce a similar shift in the expression of MHC isoforms from MHC IIb to MHC IIa, as has been shown to occur in younger subjects. This highlights the plasticity of human skeletal muscle in response to heavy resistance training, even at older ages. Key words Aging á Myosin á SDS-PAGE á Strength Introduction While examining the plasticity of skeletal muscle to chronic changes in the amount of neuromuscular activ- ity, adaptations have been seen at the level of the myosin heavy chains MHCs; Talmadge and Roy 1993). Changes in the expression of these MHC isoforms have also been observed with aging Klitgaard et al. 1990b; Larsson et al. 1993). Analysis of myosin expression in skeletal muscle has attracted a great deal of attention because changes in the phenotypic expression appear to be related to muscle function and adaptations to a variety of physiological stimuli Periasamy et al. 1989; Pette and Staron 1990). There have been no long-term studies that have examined the use of very heavy resistance training protocols in inducing changes in the expression of MHC isoforms in aged skeletal muscle. A recent study by Williamson et al. 2000) using a lower-intensity resis- tance training program found that there was a reduction in the coexpression of hybrid MHCs i.e., MHC I/IIa, Eur J Appl Physiol 2001) 84: 127±132 Ó Springer-Verlag 2001 R. U. Newton &) á W. J. Kraemer The Human Performance Laboratory, Ball State University, Muncie, IN 47306, USA e-mail: rnewton@bsu.edu Tel.: +1-765-2855139; Fax: +1-765-2853238 M. J. Sharman á M. R. M. McGuigan School of Exercise Science and Sport Management, Southern Cross University, Lismore, Australia A. HaÈkkinen Department of Physical Medicine and Rehabilitation, Central Hospital, JyvaÈskylaÈ, Finland K. HaÈkkinen Neuromuscular Research Center and Department of Biology of Physical Activity, University of JyvaÈskylaÈ, JyvaÈskylaÈ, Finland T. Triplett-McBride á J. M. McBride Department of Exercise and Sport Science, University of Wisconsin ± La Crosse, WI 54601, USA