Exercise 30 minutes once a week sufficient to improve risk factors

It doesn't take much to make a big difference. A study published in the journal Medicine & Science in Sports & Exercise shows that modest doses of eccentric exercise in particular are sufficient to improve metabolic and cardiovascular risk factors. The authors compared the effects of eccentric (muscles lengthen while resisting) to concentric exercise:

"The effects of chronic eccentric-only versus concentric-only exercise on muscle physiology and blood biochemistry were investigated."

The authors had their subjects either concentric exercise on an isokinetic dynamometer eccentric exercise using the knee extensors of both legs once a week for eight subsequent weeks. In addition to parameters of muscle function, they measured body fat, resting energy expenditure (REE); the lipid and carbohydrate oxidation rate along with blood chemistry measurements (lipid, lipoprotein and apolipoprotein profile, glucose, insulin, glycosylated hemoglobin, and creatine kinase) before and 48 hours after exercise on the first and eighth weeks of training. What did the data show?

"Acute [measured immediately after] eccentric exercise increased REE and fat oxidation at week 1 (12.7% and 12.9%, respectively) and at week 8 (0.7% and 2.8%, respectively). Chronic [measured 48 hours after] eccentric exercise increased resting REE and fat oxidation at week 8 compared with week 1 (5.0% and 9.9%, respectively). Acute eccentric exercise improved blood lipid profile at week 1 and week 8. Chronic eccentric exercise improved resting blood lipid profile at week 8. Acute eccentric exercise increased insulin resistance at week 1 but not at week 8. Chronic eccentric exercise decreased resting insulin resistance at week 8."

It's impressive to see how so little can do so much. The authors' offer a welcome conclusion:

"It is reported for the first time that only 30 min of eccentric exercise per week for 8 wk was sufficient to improve health risk factors."