ACSM'S Health & Fitness Journal:
doi: 10.1249/FIT.0b013e3181a1c20f
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Bracko, Michael R. Ed.D., FACSM

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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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WHERE AND HOW ARE KIDS ACTIVE?

This study took place in Boston, Cincinnati, and San Diego and investigated 1) what kinds of recreational sites children and adolescents used for physical activity; 2) if proximity and walking/biking to recreational sites were related to use; and 3) what neighborhood environmental factors (residential, office, retail, or public space, street design, and neighborhood features that promote walking) were associated with active transportation to recreational sites. The parents of 5- to 18-year-old children (n = 87) and matched pairs of parents and adolescents (n = 124 [adolescents, 11 to 18 years old]) were surveyed to find the use of and proximity to 12 recreational sites, if the subjects were walking or biking to the recreational sites, and the walkability and safety of the neighborhood.

Demographics of the parents of children included approximately 50% male and 50% female, 80.5% white, 9.2% black, and 5.7% other. Demographics of adolescents included approximately 50% male and 50% female, 75% white, 18.8% black, and 3.6% other.

For the children, the five most commonly used recreational sites included swimming pools, small public parks, playgrounds, fields/courts, and large parks. For the adolescents, the five most commonly used sites included fields/courts, indoor facilities, swimming pools, small and large parks, and walking/running tracks.

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The results of the survey showed that living close to recreational sites was associated with frequent use of large parks and public open space. Walking/biking to a site was associated with frequent use of most of the sites including indoor sites, small and large parks, basketball courts, walking/running tracks, school sites, playgrounds, and public open spaces. After controlling for proximity to sites and demographics, walking/biking to sites was significantly related to frequent use of four sites for children (indoor sites, walking/running tracks, school facilities, and public open spaces) and all sites except for three for adolescents.

The authors conclude that the findings of this study support the importance of community and environmental policies that facilitate safe active transport to recreational sites to promote physical activity for youth (1).

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THE BEST AB EXERCISES FOR REHAB

The purpose of this study was to compare the effectiveness of the commercially available "ab-slide," abdominal crunch/curl, supine double leg thrust/crunch, and side bridge on electromyographic (EMG) activation of the rectus abdominis, external oblique, internal oblique, and the rectus femoris muscles. The researchers wanted to understand which exercise(s) activated the abdominal muscles the most and the rectus femoris the least as they relate to low spine compressive forces in a back pain/injury rehabilitation setting. Ten males and 12 females were recruited as subjects for the study.

Subjects became familiar with each exercise 1 week before testing. The ab-slide exercise started in a quadruped position, with the subjects rolling forward until the forearms nearly touched the floor; then they rolled back to a quadruped position. The abdominal crunch started and finished in a hook-lying position, with hands lightly touching the head and feet being held by an investigator. The subjects raised the torso up until the scapulae came off the table. The supine double leg thrust/crunch started with the subject in a supine position, hips and knees flexed at 90 degrees. As the subjects extended their hips and knees, an investigator told them to stop the movement when the subject could no longer maintain contact between an investigator's fingers and the low back. The side bridge started with the subjects lying on the right side with the torso supported by the right elbow and the left foot in front of the right foot on a table. Subjects were told to raise their hips up so that the spine was straight and hold the position for 5 seconds.

The results of the study indicate that gender did not affect the performance of any of the exercises. The ab-slide produced the greatest EMG activity for the abdominal muscles and the least for the rectus femoris. The double leg thrust/crunch had high EMG activity of the rectus femoris, therefore, the authors conclude that the double leg thrust/crunch may not be a good exercise for clients with low back pain because of the torques on the pelvis and lumbar spine. The ab-slide, abdominal crunch, and side bridge would be better for clients with low back pain (3).

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TREKKING POLES HELP BURN MORE CALORIES

In this timely study, the investigators wanted to determine if trekking poles influenced physical responses to hiking on different trails and to investigate if the responses were dependent on the grade of the hiking trail. There were 14 male recreational hikers (mean age, 22.1 years).

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The subjects hiked on a trail that included sustained sections that were: 1) flat 0-1% grade; 2) steep uphill, >10% grade; 3) gradual uphill, 5% grade; and 4) gradual downhill, 5% grade. The subjects had a practice hike where they became familiar with the poles, followed 2 to 4 days later where they hiked the trail once with poles and once without poles (with rest between hikes). A second data collection was conducted 2 to 4 days later where the subjects hiked the same trail but reversed the order of using poles and not using poles. Subjects walked at a self-selected pace that was matched across trials (and trails) using split times and a metronome. Data collected included V˙O2, ventilatory efficiency (V˙E), heart rate (HR), and rating of perceived exertion (RPE).

The results indicate thatV˙O2 was significantly elevated when the subjects used poles compared with when they did not use poles. TheV˙E and HR also were significantly higher when subjects used poles compared with when they did not use poles. The RPE was not different when subjects used and did not use poles. When the physical responses were compared within each grade of trail,V˙O2,V˙E, and HR were all significantly higher when subjects hiked with poles. The RPE was not different with or without poles at any grade.

The authors conclude that using trekking poles is a useful fitness tool for increasing caloric expenditure when hiking or walking because energy production increased but the perception of effort did not (2).

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References

1. Grow HM, Saelens BE, Kerr J, Durant NH, Norman GJ, Sallis JF. Where are youth active? Roles of proximity, active transport, and build environment. Med Sci Sports Exerc. 2008;40(12):2071-9.

2. Saunders MJ, Ryan Hipp G, Wenos DL, Deaton ML. Trekking poles increase physiological responses to hiking without increased perceived exertion. J Strength Cond Res. 2008;22(5):1468-74.

3. Youdas JW, Guck BR, Hebrink RC, Rugotzke JD, Madson TJ, Hollman JH. An electromyographic analysis of the ab-slide, abdominal crunch, supine double leg thrust, and side bridge in health young adults: implications for rehabilitation professionals. J Strength Cond Res. 2008;22(6):1939-46.

© 2009 American College of Sports Medicine

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