Resistance Training and Chronic Disease
Ciccolo, J. T., Carr, L. J., Krupel, K. L., & Longval, J. L. (2009). The Role of Resistance Training in the Prevention and Treatment of Chronic Disease. American Journal of Lifestyle Medicine, 4, 293-308.
Since research has shown benefits resistance training (RT) can afford in adults' physical and mental health, the authors provide an overview of the current information, demonstrating the role of RT in adults with or at risk for chronic disease.
The authors reviewed randomized controlled trial studies with adults that were printed or published through February, 2009. However, did not include any studies that focused on combined aerobic and resistance exercise. Instead, the focus is on studies that described unique and independent effects derived from RT- only programs. This article reviews the literature, and discusses findings within each chronic disease area.
For cardiovascular disease, there are three areas where RT is starting to make an impact, but is still in debate. With hypertension, though some beneficial changes were reported, and the safety and efficacy of using RT to combat high blood pressure were illustrated, the review did recognize that caution should be used when interpreting results given the significant limitations in the existing studies. For arterial stiffness, high intensity RT has shown some negative effects on central arterial stiffness, however, programs using moderate intensity or volume do not. Though the authors acknowledge that longer trials are needed to investigate this, physicians should not avoid recommending moderate intensity RT based on the existing evidence. For chronic heart failure, recent research has shown that RT may play an important role for this population, including improving functional measures of health, but there is debate over the exercise prescription; and the authors stress the importance of tailoring a program to fit an individual's specific needs.
Regarding metabolic diseases, it is pretty widely recognized that RT can affect metabolism. But, specific to obesity, RT independent of aerobic exercise has mixed support for reducing body weight. It does, however, seem to have significant support for being a valuable and effective weight management tool, which does itself have important implications for preventing, and managing overweight and obesity issues. The challenge here does seem to be the adoption and maintenance of an RT program in this population. With type 2 diabetes, RT may help manage the risk of acquiring it, and it still remains clear that it is beneficial to those who already have type 2 diabetes. However, the mechanisms responsible for the improved insulin sensitivity are still uncertain; and the authors call for further investigation into the issues of exercise time, intensity, frequency, and adherence. RT programs have typically shown little to no effect in hyperlipidemia, but more recent results have indicated that RT can have a positive effect on lipids. However, as often said in research, results should be interpreted with caution as there were significant limitations in the studies. RT has gained some attention with chronic kidney disease/end-stage renal disease, given its potential to combat negative changes in muscle function and size. More recent research findings have even given reason for experts in this field to have called for widespread dissemination, and promotion of exercise as adjunct therapy to dialysis.
Recent reviews have shown that RT may be able to combat many side effects of cancer, which can benefit in both long and short-term situations. Specifically, results have demonstrated that moderate-intensity RT can be very successful in prostate cancer. In breast cancer, the independent effect of RT isn't as clear, but health-related, as well as clinical benefits have been reported, including improved compliance with chemotherapy. Here again, exercise prescription needs to be further investigated.
Using a multidimensional approach (varying intensity, velocity, and frequency) in aging/older adults has shown success in improving physical function, but further studies examining the underlying mechanisms are warranted. There is little doubt that RT is the optimal intervention in reducing sarcopenia, but determining how on a molecular level is the next step. Regarding balance, the authors noted that the current literature does not provide much support for RT of increasing balance in older adults, but rather the most effective interventions were those that focused on balance training.
Regarding orthopedic conditions, research has consistently shown bone to have a beneficial site-specific response to high-intensity RT, although a systemic response is possible, and this is something that warrants more focused research on the matter. The results of this review were also in alignment with a recent evidence-based review that supported the efficacy of RT as treatment for osteoarthritis of the knee, though the authors called for more (higher quality) research on other joints, such as the hip.
In neuromuscular disorders such as stroke, though there are concerns of potential adverse effects of RT in terms of individuals with already increased muscle tone, those concerns were generally unfounded, and RT determined to be both safe and effective. Here again, the issue lies in determining optimal frequency, duration, and timing of beginning an RT program. Optimal prescription is also a future research goal in fibromyalgia given that improvements have been shown in pain, well-being, and tender points, but these studies were considered low-quality, and pilot or quasi-experimental studies. Similarly, with multiple sclerosis (MS), RT appears to be beneficial. However, there are a limited number of studies on this condition, and many of these do not have high methodological quality. Here too, not only do we need more high-quality evidence of its benefits, but studies should also seek to determine how to use an RT program to manage the daily symptoms, and fluctuations of symptoms present in MS. RT has just begun to be looked at in Parkinson disease, (PD) but with promising results, possibly carrying the potential to reduce the severity of the neuromuscular symptoms experienced with PD. Larger and more comprehensive trials are needed to assess the full range of symptoms and side effects associated with PD.
Although, few studies have looked at only RT as an intervention for depression, there is evidence that RT can induce improvements, and more research is needed to show the mechanistic links. Positive reports continue to increase the literature base regarding RT and HIV/AIDS, suggesting that it is both safe and beneficial; though given the fact that there have not been a large number of studies and these interventions were all under 16 weeks - again the results should be interpreted with caution. As with HIV/AIDS, investigations into the use of RT- only programs for individuals with COPD have shown great promise, specifically due to the fact that RT places less demand on the respiratory system, while potentially still achieving benefits. Future studies are needed to look at these effects long-term, and assess factors that predict adherence to an RT program.
Though it seems clear that resistance training can create many health-related benefits in various disabilities and chronic health conditions; overall, there is a need for larger, higher quality studies that look into more specific aspects of symptoms, side-effects, adoption, adherence, and exercise prescription. The authors also acknowledged that most of the existing research uses supervised, facility-based programs with expensive equipment and in order for programs to ultimately be effective in the general public; they need to be able to be disseminated more easily.
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