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Research Bites

Bracko, Michael R. Ed.D., FACSM

doi: 10.1249/FIT.0b013e3181ed5990

Diet or Exercise: Which is Better for Metabolic Fitness?; Stretch and You Get Stronger!; Benefits of Kettlebell Swings; Amino Acids Help Resistance Training.

Michael R. Bracko, Ed.D., FACSM, is an exercise physiologist and director of the Institute for Hockey Research and the Occupational Performance Institute in Calgary, Canada. He is an associate editor for ACSM's Health & Fitness Journal® and works in three areas: 1) sports physiology, where he conducts research on the performance characteristics of female ice hockey players, teaches high performance skating, and serves as physiologist for the University of Alberta Women's Hockey Team and the U.S. Men's Deaf Olympic Ice Hockey Team; 2) the health and fitness industry, by contributing to fitness magazines, consulting, presenting at health and fitness meetings such as the ACSM's Health & Fitness Summit & Exposition; and 3) as an occupational physiologist in the areas of back injury prevention, ergonomics, workstation stretching, and prework warm-up.

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In this timely study, the researchers investigated whether a program of calorie restriction with and without aerobic exercise that produces equal changes in fatness leads to improved cardiometabolic benefits when exercise is added. A total of 36 subjects (20 female and 16 male subjects) were randomly assigned to one of three groups for a 6-month intervention: control (weight-maintenance diet), calorie restriction (25% reduction in energy intake), and calorie restriction plus aerobic exercise (12.5% reduction in energy intake plus 12.5% increase in exercise energy expenditure).

Food was provided during weeks 1 to 12 and 22 to 24. All diets were based on the American Heart Association Step 1 recommendations (≤30% fat, ≤10% saturated fat). During weeks 13 to 21, subjects self-selected their own diet based on their caloric target. The calorie restriction plus aerobic exercise group exercised 5 days per week by walking, running, or riding a stationary bike. Pretesting and posttesting was conducted on the following variables: fat mass, visceral fat, V˙O2peak, isokinetic knee extension and flexion, blood lipids, blood pressure, and insulin sensitivity/secretion.

The results show that the calorie restriction plus aerobic exercise group improved V˙O2peak but not isokinetic strength. There were no differences in losses of weight, fat mass, visceral fat, and systolic blood pressure. However, the good news is that only the calorie restriction plus aerobic exercise group had significant decreases in diastolic blood pressure and low-density lipoprotein cholesterol and a significant increase in insulin sensitivity. The authors conclude that these results help support the addition of exercise in the debate about "diet or exercise" for weight loss as it relates to improving metabolic fitness (3).

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The purpose of this study was to investigate the differences in lower-body strength gains when using weight training versus weight training combined with static stretching. A total of 32 college students (16 women and 16 men) who were not actively involved in weight training were matched according to sex and knee extension one repetition maximum. One subject from each pair was randomly assigned to the weight-training group or the weight-training and stretching group.

Each group did the same weight-training protocol: three sets of six repetitions of knee extension, knee flexion, and leg press 3 days per week for 8 weeks, with weekly increases in weight lifted. The stretching group additionally performed 30 minutes of static stretching, 2 days per week. They stretched the following muscles: hamstrings, quadriceps, hip adductors, hip abductors, hip external rotators, hip internal rotators, plantarflexors, and dorsiflexors. Each stretch was held for 15 seconds and repeated three times with a 15-second rest period between stretches. The stretching was done on days when the group did not weight train.

The results indicate that the weight-training group significantly increased their knee flexion, knee extension, and leg press one repetition maximum by 12%, 14%, and 9%, respectively. However, the weight-training and stretching group significantly increased their knee flexion, knee extension, and leg press one repetition maximum by 16%, 27%, and 31%, respectively. In addition, the weight-training and stretching group had significantly greater knee extension and leg press increases than the weight-training group.

The authors conclude that for beginning weight trainers, performing static stretching on the days they are not weight training can help maximize their strength gains for 8 weeks. This is good news about the benefits of static stretching after so many years of so-called bad news about stretching (2).

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Considering the popularity of alternative forms of exercise being used in group exercise programs, this research is timely and appropriate. The purpose of this study was to quantify the aerobic challenge of a Kettlebell exercise called the "U.S. Department of Energy Man-Maker." This exercise consists of holding the Kettlebell with two hands and starting with the Kettlebell between bent knees. The movement of the Kettlebell is to swing it up with both hands above the head then down through the legs as the knees bend.



Ten college-aged male subjects were in the study. The subjects completed a graded exercise test to exhaustion to determine V˙O2max. Two to seven days after the test, the subjects were instructed to complete as many two-handed swings as they could in 12 minutes with a 16-lb Kettlebell. During the Kettlebell swings, the subjects were analyzed for V˙O2 and heart rate.

The results show that the subjects completed an average of 265 ± 68 swings for an average work rate of 22 ± 6 swings per minute. Relative V˙O2 averaged 34.31 ± 5.67 ml/kg/min (65.3 ± 9.8% of V˙O2max) during the swings, which amounted to an accumulated oxygen consumption of 26.5 ± 4.78 L/min. The heart rate of the subjects was 165 ± 13 beats per minute (86.6 ± 6.0% of heart rate maximum) during the swings. The average percentage heart rate maximum during the Kettlebell swings was significantly higher than the average %V˙O2max.

The authors conclude that the Kettlebell "Man-Maker" exercise seems to produce a greater challenge to the cardiovascular system than has been shown with circuit weight training (1).

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This study investigated the effects of short-term amino acid supplementation on maintenance of a net anabolic hormonal profile and decreased muscle cell damage during high-intensity resistance training. The resistance training was a protocol of "overreaching." Overreaching is a short training phase in which the volume and/or intensity is increased beyond normal. Eight resistance trained male subjects (22.9 years old) were randomly assigned to either a branched chain amino acid group or a placebo group.



The methodology consisted of a balanced, crossover, placebo-controlled, double-blind, repeated-measures design where subjects acted as their own control. Each treatment was taken for three weeks followed by a fourth week of supplementation and weight training. Then, there was a 5-week "washout" period with no supplementation or weight training. Finally, there was a 4-week supplementation period where the groups took the other treatment.

Weight training included 4 supervised sessions between days 22 and 28 of supplementation. The sessions consisted of 5 minutes of passive stretching followed by 3 sets of 6 to 8 repetitions at 80% of one repetition maximum of the following exercises: leg press, leg curl, leg extension, chest press, military press, lat pull down, dumbbell curl, and triceps press down. Subjects were tested for one repetition maximum on all exercises 2 weeks before consuming the treatments. In addition, blood was drawn before and after supplementation and, again, after 2 and 4 days of training. Blood was analyzed for testosterone, cortisol, and creatine kinase.

The results indicate that testosterone levels were significantly higher, and cortisol and creatine kinase were significantly lower in the branched chain amino acid group. The authors conclude that during periods of "overreaching," consumption of branched chain amino acids may increase an athlete's ability to train harder because of increased testosterone and a reduced risk of injury or illness (4).

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1. Farrar RE, Mayhew JL, Koch AJ. Oxygen cost of Kettlebell swings. J Strength Cond Res. 2010;24(4):1034-6.
2. Kokkonen J, Nelson AG, Tarawhiti T, Buckingham P, Winchester JB. Early-phase resistance training strength gains in novice lifters are enhanced by doing static stretching. J Strength Cond Res. 2010;24(2):502-6.
3. Larson-Meyer DE, Redman L, Heilbronn LK, Martin CK, Revussin E. Caloric restriction with or without exercise: the fitness versus fatness debate. Med Sci Sports Exerc. 2010;42(1):152-9.
4. Sharp CPM, Pearson DR. Amino acid supplements and recovery from high-intensity resistance training. J Strength Cond Res. 2010;24(4):1125-30.
© 2010 American College of Sports Medicine.