Novel all-extremity high-intensity interval training improves aerobic fitness, cardiac function and insulin resistance in healthy older adults
Introduction
Aging induces cardiac remodeling and changes in cardiac function that lead to increased risk of cardiovascular disease (CVD) (Fleg and Strait, 2012). Improving aerobic fitness lowers the risk of CVD mortality (Lee et al., 2011), however, the optimal training regimen for improving aerobic fitness in older adults remains undefined. High-intensity interval training (HIIT) has been reported to have superior effects on aerobic fitness, cardiac function, lipids and glucose control compared with moderate-intensity continuous training (MICT) in patients with cardiometabolic disease (Molmen-Hansen et al., 2012, Rognmo et al., 2004, Tjonna et al., 2008, Wisloff et al., 2007). The HIIT protocol in these studies consists of 4-min intervals of high-intensity treadmill walking (usually “uphill”) interspersed with periods of moderate-intensity walking. However, older adults frequently experience balance and musculoskeletal problems (Gheno et al., 2012) which limit the feasibility of weight-bearing exercise and in particular high-intensity treadmill walking. Development of an alternative exercise modality for HIIT that avoids the age-related limitations of treadmill walking is necessary for older adults. The use of a stationary cycle eliminates balance and weight-bearing concerns, and is likely to be more suitable as a long-term exercise routine for older adults. More importantly, use of an all-extremity ergometer increases the active amount of muscle mass during exercise compared to lower extremity exercise, allows compensation for unilateral or bilateral lower extremity weakness or fatigue, and ultimately affords a larger proportion of older individuals to undergo HIIT.
Therefore, we sought to evaluate the feasibility and safety of performing HIIT on a non-weight-bearing all-extremity ergometer in previously sedentary older adults. In addition, we tested the hypothesis that 8 weeks of all-extremity HIIT will be more effective in improving aerobic fitness, cardiac function, and metabolic risk factors compared with all-extremity MICT in healthy sedentary older adults.
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Subjects
Subjects were 55–79 years old, sedentary, non-smokers who were free of cardiovascular and other major clinical disease (e.g., diabetes, liver and renal disease) as assessed by medical history, physical examination, resting blood pressure, ECG and blood analysis (i.e., comprehensive metabolic panel, lipid panel, insulin, and complete blood count with differential). In addition, all subjects demonstrated normal ECG and blood pressure responses to a clinically-supervised diagnostic graded exercise
Feasibility and safety of novel all-extremity HIIT
Previously sedentary older adults completed 8 weeks of HIIT or MICT using synchronous arm and leg exercise on a non-weight-bearing air-braked ergometer. No adverse events occurred in HIIT or MICT groups (i.e., deaths, nonfatal serious events such as myocardial infarction and musculoskeletal problems, or other serious or non-serious health issues requiring hospitalization or medical treatment). However, during the first few HIIT or MICT exercise sessions the majority of subjects reported
Discussion
We have established that this novel approach of performing HIIT on a non-weight-bearing all-extremity ergometer is feasible in healthy sedentary older adults and safe. This is the first randomized controlled trial to provide evidence that non-weight-bearing all-extremity HIIT, but not MICT, improves aerobic fitness, cardiac systolic function, and insulin resistance without affecting body weight and composition in older adults who are free of cardiovascular and major clinical disease. Left
Conclusions
The present study demonstrates that HIIT on a non-weight-bearing all-extremity ergometer is feasible in previously sedentary older adults and safe. All-extremity HIIT is more effective in improving aerobic fitness, cardiac systolic function, and insulin resistance compared with isocaloric MICT. HIIT on a non-weight-bearing all-extremity ergometer represents a promising alternative to weight-bearing HIIT in sedentary older adults.
Acknowledgments
We would like to express our gratitude to the study participants for their time and efforts. We would also like to thank John Larocca, Karen Mackay, Andrea Vasconez, Sofia Sofianos, Kevin Priddy, Andre Revell, Austin Nolz, Blake Dalley, Lily Malone, Jessica Howard and Lindsay Wainman who assisted with conducting this intervention.
This work was supported by NIH AG 050203 to DDC. The funding source had no involvement in preparation or completion of the study or writing of the article.
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