Muscle strength and other measures of physical function decline with age (e.g., Kenny et al. 2013). To overcome these age-related decrements in physical function, physical exercise is recommended (e.g. American College of Sports Medicine 2009; Australian Government Department of Health 2005). Two types of exercise that improve physical function in older adults are strength training and power training. Strength training involves lifting a heavy load at a controlled speed, whereas power training involves lifting a moderate or heavy load as fast as possible. Strength training improves muscle strength, and in some cases walking speed, in older adults (see Latham et al. 2004 for review). Power training also improves physical function in older adults, and when direct comparisons have been made between the two types of exercise, the functional benefits derived from power training have been greater or equal to that from strength training (e.g., Miszko et al. 2003; Bottaro et al. 2007; see McKinnon et al. 2016 for review).
Earlier this year, a group of researchers in Denmark published results from a randomized-controlled trial that explored the merits of power training in older adults (Hvid et al. 2016). The researchers examined whether 12 weeks of power training could improve walking speed and voluntary activation (i.e., the nervous system’s ability to “drive” the muscle to produce its maximal force) in men and women who had slow walking speeds and were over 75 years of age. The participants were randomly allocated into a power training group or a control group. Participants in the power training group completed 24 sessions (2 sessions per week for 12 weeks) of physical exercise in which the intent of each exercise was to move a heavy load (70-80% of maximum) as rapidly as possible. Participants in the control group did not undergo training. Leg strength, walking speed, muscle thickness, and voluntary activation were the study outcomes.
WHAT WAS FOUND?
Leg strength, walking speed, and voluntary activation improved in the power training group, but not the control group. Participants in the training group were able to produce more force (+13.4 newton meters), walk faster (+0.12 meters per second), and “drive” the muscles more (+6.2%) than controls. The improvement in voluntary activation was correlated with the improvement in walking speed. Muscle thickness did not change. The results suggest that adaptations in the nervous system, rather than the muscle, were responsible for the improvements in leg strength and walking speed.
SIGNIFICANCE AND IMPLICATIONS
The study demonstrates that 12 weeks of power training can improve leg strength, walking speed, and voluntary activation in mobility-limited older adults. The findings are important because leg strength, walking speed, and voluntary activation are all impaired in ageing. Thus, power training can be used to combat age-related decrements in physical function.
One of the limitations of the work is that little information was provided on the specific power-training movements that were performed by the participants. The researchers reported that the training included, “upper-body, balance, and lower-body exercises with specific emphasis on leg press and plantarflexion.” This limited description prevents researchers from being able to replicate the study, and more information is needed for clinicians to be able to prescribe these exercises to patients.
Nevertheless, the study findings are in line with previous work, which has shown that when older adults regularly move loads as hard and fast as possible, their physical function improves.
Hvid LG, Srotmeyer ES, Skjodt M, Magnussen LV, Andersen M, Caserotti P (2016). Voluntary muscle activation improves with power training and is associated with changes in gait speed in mobility-limited older adults: a randomized controlled trial. Exp Gerontol 80, 51-56. doi: 10.1016/j.exger.2016.03.018.
American College of Sports Medicine, Chodzko-Zajko WJ, Proctor DN, Fiatarone Singh MA, Minson CT, Nigg CR, Salem GJ, Skinner JS (2009). Exercise and physical activity for older adults. Med Sci Sports Exerc 41, 1510-1530. doi: 10.1249/MSS.0b013e3181a0c95c.
Australian Government Department of Health, Brown WJ, Moorhead GE, Marshall AL (2005). Choose Health: Be Active: A physical activity guide for older Australians. Canberra: Commonwealth of Australia and the Repatriation Commission. P01001.
Bottaro M, Machado SN, Noqueira W, Scales R, Veloso J (2007). Effect of high versus low-velocity resistance training on muscular fitness and functional performance in older men. Eur J Appl Physiol 99, 257-264. doi:10.1007/s00421-006-0343-1.
Kenny RA, Coen RF, Frewen J, Donoghue OA, Cronin H, Savva GM (2013). Normative values of cognitive and physical function in older adults: findings from the Irish Longitudinal Study on Ageing. J Am Geriatr Soc 61, S279-S290. doi: 10.1111/jgs.12195.
Latham NK, Bennett DA, Stretton CM, Anderson CS (2004). Systematic review of progressive resistance strength training in older adults. J Gerontol A Biol Sci Med Sci 59, 48-61. doi: 10.1093/gerona/59.1.M48.
McKinnon NB, Connelly DM, Rice CL, Hunter SW, Doherty TJ (2016). Neuromuscular contributions to the age-related reduction in muscle power: mechanisms and potential role of high velocity power training. Ageing Res Rev doi: 10.1016/j.arr.2016.09.003.
Miszko TA, Cress ME, Slade JM, Covey CJ, Agrawal SK, Doerr CE (2003). Effect of strength and power training on physical function in community-dwelling older adults. J Gerontol A Biol Sci Med Sci 58, 171-175. doi: 10.1093/gerona/58.2.M171.