Active Voice: A Stiff Debate – Resistance Training and Arterial Health
By Jason S. Au, B.Sc.Kin., and Maureen J. MacDonald, Ph.D.
Jason S. Au, B.Sc.Kin., is a Ph.D. candidate at McMaster University in Hamilton, Canada and is training under the supervision of Maureen J. MacDonald, Ph.D.
Maureen J. MacDonald, Ph.D. is director of the School of Interdisciplinary Science at McMaster University. She directs the Vascular Dynamics Lab in the Department of Kinesiology. Her current research relates to the complex interaction between the mechanical, neural and humoral factors in peripheral arteries in response to both acute and chronic changes in physical activity.
This commentary presents the authors’ views on the topic of their research article, which they and their colleagues had published in the February 2017 issue of Medicine & Science in Sports & Exercise® (MSSE).
How do you assess the effectiveness of an exercise program? The average exerciser is likely focused on tangible outcomes such as weight loss, lower blood pressure or improved mood. From a clinical scientist’s point of view, it is equally important to evaluate the long-term effects of exercise on disease risk and mortality through the study of biomarkers or predictive outcomes. Interestingly, the usual monitoring tools (such as blood lipids, blood glucose and blood pressure) don’t completely predict exercise training-related improvements in cardiovascular disease risk, e.g. Mora and colleagues, 2007. In recent years, vascular health has been investigated as a potential focus for explaining and tracking exercise training related improvements in cardiovascular disease risk, as it seems to predict future cardiovascular events effectively.
A primary variable that reflects vascular health is arterial stiffness, an index that describes the pressure-buffering capacity of an arterial segment as the forward blood pressure wave travels through the vascular tree. When measured in the central elastic arteries, arterial stiffness is strongly predictive of future cardiovascular disease events, especially in adults with intermediate risk (Ben-Shlomo et al., 2014). While the measurement of arterial stiffness has not yet been included in North American cardiovascular disease risk assessment recommendations, it has been integrated into the European Society of Cardiology guidelines for hypertension risk.
The assessment of improvements in arterial stiffness with exercise training interventions is an ongoing line of research. Currently, there is no agreement in the literature as to whether arteries get stiffer or more elastic with resistance training. Given that improvements (reductions) in arterial stiffness might be related to improvements in health, it would be of considerable interest to determine if an activity as beneficial to health as resistance exercise training (Shiroma et al., 2017) led to increased cardiovascular disease risk.
In our randomized controlled trial, published in the February 2017 issue of MSSE, we investigated whether 12 weeks of resistance exercise training with different training loads would affect arterial stiffness in previously resistance-trained young men. We originally hypothesized that a training program of higher versus lower repetitions per set (20-25 versus 8-12 repetitions per set) might offset any observed increase in arterial stiffness since it would be expected to be associated with a lower blood pressure stimulus during training. Instead, we found an improvement (reduction) in arterial stiffness in both the high and low repetition resistance training groups compared to controls. While we were unable to explain exactly why arterial stiffness improved in our two training groups, the strengths of our study included the use of multiple criterion standard techniques for stiffness assessment and a high-quality study design, including a non-exercising control group.
Currently, there are no ACSM recommendations on resistance training for cardiovascular health. Nonetheless, our findings show a beneficial impact of resistance training on arterial stiffness, a message that is consistent with recent observational data we cited above from Shiroma et al., 2017. Thus, aside from the traditional understanding of the role for resistance exercise for improving muscular strength, it appears that resistance training also offers many other benefits – such as those related to cardiovascular risk reduction. Specifically, these include improvements in body composition, greater functional mobility and glucose control. Resistance training, thus, should be encouraged and enjoyed by all ages to promote health.