MAY. 15, 2014
WASHINGTON – Eccentric exercise in the form of downhill walking is a promising new means of reducing elevated liver enzyme levels in overweight and obese sedentary individuals.
This finding suggests this form of exercise may have a role as a therapeutic intervention in patients with nonalcoholic fatty liver disease, a condition which is rapidly growing in prevalence and which is associated with increased risks of diabetes and cardiovascular events, Dr. Christoph Saely observed at the annual meeting of the American College of Cardiology.
It’s known that physical exercise can be effective in lowering elevated hepatic enzymes, but it’s equally clear that conventional forms of exercise such as stair-climbing, jogging, and brisk walking are too vigorous and demanding for many obese sedentary patients. They’re unable to get with the program.
That’s where eccentric training holds particular value, according to Dr. Saely of the Academic Teaching Hospital of Feldkirch, Austria.
Eccentric exercise occurs when active muscle contraction occurs simultaneously with the muscle’s lengthening. Thus, it involves active resistance to stretching. During a biceps curl, for example, the eccentric muscle work occurs as the weight is being lowered, while concentric muscle training happens as the weight is being raised. Similarly, walking uphill involves concentric muscle contraction, while walking downhill emphasizes eccentric muscle action.
Eccentric exercise training creates more force yet uses less energy. It protects joints from damage. Physical therapists and fitness trainers find eccentric exercise regimens are particularly useful in the elderly, infirm, and sedentary because such individuals find it less exhausting and they are more willing to participate.
Dr. Saely and his coinvestigators have an ideal outdoor laboratory in which to conduct a pilot study of the effects of eccentric exercise because their hospital is located in the Austrian Alps. Subjects can hike downhill, then take a cable car back up, with adherence to the program monitored electronically at the vehicle entrance.
He reported on 42 overweight or obese sedentary patients with elevated liver enzymes and 12 matched controls who were assigned to hike down a predefined route in the Alps three to five times per week for 8 weeks. The course featured a 540-meter drop in altitude.
Mean serum alanine aminotransferase levels in the overweight group dropped from 36 IU/L at baseline to 31 IU/L at 8 weeks. Serum gamma-glutamyl transferase fell from 56 IU/L to 44 IU/L. And the alanine aminotransferase/aspartate aminotransferase ratio improved from 1.22 IU/L to 1.02 IU/L. Meanwhile, liver enzyme levels remained unchanged over time in the controls.
The eccentric exercise regimen was well tolerated, participation was high, and there were no serious adverse events, according to Dr. Saely.
While not everyone is fortunate enough to have a mountain in the backyard with a gondola for the return trip, knowledgeable fitness instructors can demonstrate eccentric exercises using weights and machines that target large muscle groups.
Dr. Saely reported having no conflicts of interest regarding this study.