July 15, 2007
Exercise ETC’s Review of Exercise Related Research
Compiled by Chris Marino, MS, CSCS
Director of Education, Exercise ETC
High Intensity Intervals Effective in High Risk Population
It is widely accepted that High Intensity Interval Training (HIIT) increases both fat loss and performance to a greater extent than Moderate Continuous Training (MCT). Unfortunately, young, healthy subjects have been used for the bulk of research while groups who may experience the greatest health or life-saving benefits have yet to be studied... until now.
Researchers from Norway compared the benefits of HIIT to MCT in a group of twenty-seven patients (median age of 75) with stable post-infarction heart failure. All participants were undergoing treatment with B-blockers and angiotensin-converting enzyme (ACE) inhibitors. Pre-participation left ventricular [LV] ejection fraction averaged 29% and VO2peak, just 13 ml/kg/min.
The patients were divided into three groups: 1. Moderate Continuous Training (MCT), 2. Aerobic Interval Training (AIT), and 3. Control.
Each group exercised 3 times per week, two of which were supervised for the MCT and AIT groups only. The control group met for supervised exercise once every 3 weeks. The MCT group exercised between 70% and 75% of peak heart rate (HRpeak) for a total of ~47 minutes including warm-up and cool-down. The AIT group completed four 4-minute intervals with 3-minute active rest periods at 50-60% of HRpeak. Total exercise time for AIT was just under 40 minutes including warm-up and cool-down. Total calorie expenditure was matched for all groups.
The results for the AIT group after 12-weeks of training were astounding. VO2peak increased by 46% compared to just 14% for the MCT group. Left Ventricular end-diastolic and end-systolic volumes declined by 18% and 25%, respectively in AIT, but not MCT or controls. LV ejection fraction increased 35%. Additional improvements included improved mitochondrial function and improved endothelial function. Significant improvements in quality of life measured occurred in both experimental groups.
It's important to note that the American College of Sports Medicine continues to support medically supervised exercise for patients with low ejection fraction (<50%) style="font-style: italic;">Circulation: 115:3086-3094.
BMI in Kids Does Not Predict BMI in Adults
Previous research has found Body Mass Index (BMI) during adolescence to be highly predictive of BMI in adulthood. Consequently, many healthcare professionals use BMI as a tool to classify individuals as overweight or obese in effort to educate and intervene. Unfortunately, BMI is not the best indicator of obesity because it does not take into consideration the difference between lean mass and fat mass; fat mass which is highly correlated with chronic diseases of the heart and metabolic systems. A recent study suggests that skinfolds, which are not only a better tool for evaluating body fat, may be a better option in predicting overweight in adulthood.
Researchers followed 350 participants over 25 years during which BMI and skinfold thickness were assessed on 8 occasions. A comparison was made between values obtained during adolescence (ages 12-16) and at a mean age of 37 for adults. Adolescent measurements indicated that no boys and just 1.7% of girls were overweight at the time. Adult measurements concluded that 29% of men and 32% of women were overweight. Comparisons at age 37 were performed using dual-energy X-ray absorptiometry.
In the end, the association of skinfold thickness with adult body weight was more pronounced than the relationship of BMI. Those individuals with the greatest skinfold measurement had two to four times the risk of being over-fat in adulthood.
The authors contend that assessing skinfold should be the preferred method for identifying risk for obesity amongst teenagers. The findings also imply the need for weight-management programs and interventions to begin prior to adolescence.
Nooyens, A.C.J., et al (2007) Adolescent skinfold thickness is a better predictor of high body fatness in adults than is body mass index: the Amsterdam Growth and Health Longitudinal Study. American Journal of Clinical Nutrition. Vol. 85, No. 6, 1533-1539.
Vastus Medialis Has Greater Role Than Once Thought
Degeneration, injury and pain are all consequences of instability at the knee joint. A weak VMO or Vastus Medialis Oblique, which has been thought to act both as a stabilizer of the patella and as a knee extensor, is often the culprit in cases of knee pain or injury. Unfortunately, studies have not unanimously agreed on the exact function of the VMO and as a result therapeutic strategies to prevent and treat injuries may be insufficient. The discrepancies lie with the methodology of most research on the VMO, which has been performed during non-weight bearing or non-functional activities. To better understand VMO function, researchers evaluated its relative contribution during weight-bearing activities.
Ten participants completed both bilateral and unilateral drop jumps (DJ) and squat jumps (SJ) on a force platform while electrical activity in the Vastus Lateralis (VL) and VMO region of the Quadriceps Femoris was measured.
The most significant finding of this study was that the relative contribution of the VMO during single leg jumps was significantly greater than the VL. The authors simultaneously conducted 6 cadaver dissections during which they identified a distinct nerve supply to the VMO. This contrasts previous findings and suggests that the VMO can act independently of the quadriceps group.
The researchers concluded that the VMO is indeed an important stabilizer of the patella in the trochlear groove. As such, this muscle can be trained most effectively using single leg closed-chain strength exercises and plyometrics to increase functional activation of the VMO.
Toumi, H., et al (2007) New Insights into the Function of the Vastus Medialis with Clinical Implications. Medicine and Science in Sports and Exercise. 39(7): 1153-1159.
New Link Between Vitamin D & Function in Older Adults
Vitamin D has several important functions in the body including regulating calcium and phosphorus levels in the blood, supporting formation of new bone, and helping suppress tumor formation. Although Vitamin D deficiency is relatively uncommon in young, healthy populations who spend a sufficient amount of time in the sun, it is found in elderly populations with increasing frequency. In elderly populations Vitamin D deficiency has been suggested to result in bone loss, fractures, and muscle weakness. Now researchers in the Netherlands are suggesting that decreased performance/function be included on that list.
Researchers monitored Vitamin D levels in nearly 1,000 elderly individuals age 65+ over a 3-year period during which performance variables were also tracked (i.e. walking test, chair sit-to-stands, and tandem stand). Approximately one-half of the participants were determined to be Vitamin D deficient at the start of the study. The researchers found that performance was poorer in participants with sub-optimal Vitamin D levels and that those same individuals exhibited greater declines in performance over the 3-year period.
The researchers are encouraging more awareness of the potential for insufficient Vitamin D in elderly persons.
Wicherts, I.S., et al (2007) Vitamin D Status Predicts Physical Performance and Its Decline in Older Persons. The Journal of Clinical Endocrinology & Metabolism. 92(6): 2058-2065.