Walking: The Latest Research
We all know the basics on walking: It’s simple, inexpensive and brimming with health benefits. Yet, in an age when exercise technology is increasingly complex and trainers’ clients are developing more sophisticated tastes, questions linger: How can walking provide a worthwhile workout, and how well does walking burn calories? These and many other walking-related issues are explored in this review, which highlights research understandings on calorie burning and presents several evidence-based ideas for incorporating newer strategies in your walking exercise program designs.
Traditional walking strategies are not for everyone. They may not provide enough challenge for people of above-average fitness, or they may be too difficult for those who suffer from ambulatory physical limitations. Still, walking is excellent exercise for a broad cross-section of the population. The following seven questions address key topics about walking.
1. What Is an Adult’s Natural Walking Pace, and Why?
Most healthy adults tend to naturally select a walking pace of approximately 2.8 miles per hour (Willis, Ganley & Herman 2005). Researchers hypothesize that the central nervous system selects a preferred walking speed to lessen the body’s energy expenditure (Martin, Rothstein & Larish 1992). Another theory is that preferred walking speed reflects changes in fuel use: In most adults, fat is the primary fuel source at speeds up to 2.8 mph, which serves as a metabolic walking threshold speed (Willis, Ganley & Herman 2005). Above this speed, carbohydrate oxidation (breakdown) increases rapidly, resulting in a perception of greater effort because carbohydrates are a limited fuel source compared with fat. As a result, preferred walking speed appears to happen naturally, as the body seeks out the most economical fuel conditions in the muscle when fat oxidation is the primary fuel source.
Aging and inactivity often diminish the musculoskeletal functioning of the lower-body gait muscles (Martin, Rothstein & Larish 1992). This may require the body to recruit additional motor units and perhaps a higher proportion of less-economical fast-twitch muscle fibers (which are fueled predominantly by carbohydrate) in order to generate the force required for walking. This is why the elderly see a decline in walking speed and a change in gait characteristics.
2. What Is “Brisk” Walking?
Exercisers are often urged to take a “brisk” walk, but the idea of a “brisk” pace is open to interpretation. A brisk walk for some is a leisurely stroll for others.
A good starting point is the American College of Sports Medicine’s (ACSM 2014) recommendation that most adults accumulate 30-60 minutes a day of moderate-intensity exercise at least 5 days a week, or 20-60 minutes a day of vigorous-intensity exercise at least 3 days a week—or a combination of the two.
How do walking exercisers determine whether their moderate-intensity walk meets ACSM guidelines? Scientifically, walking at an intensity of 3-6 METs (metabolic equivalent of task is a physiological measure expressing the energy cost of physical activities) is considered moderate-intensity exercise.
Counting steps is another practical way to measure intensity. Marshall et al. (2009) determined that walking at approximately 100 steps per minute is moderate-intensity exercise. At 100 steps per minute, a walker can meet current recommendations for moderate-intensity physical activity by walking at least 3,000 steps in 30 minutes at least 5 days a week. This can easily be tracked with any pedometer or pedometer app on a smartphone. A walker could also accumulate three daily walks of 1,000 steps in 10 minutes on 5 days each week.
Murtagh, Boreham & Murphy (2002) examined 82 recreational walkers who selected their own perceptions of a “brisk” walking pace. Overall, the subjects walked at an average of about 3.5 mph and were able to accurately reach moderate-intensity exercise levels by self-selecting their pace. Older adults (aged 60-85 years) had an average self-selected walking pace of 3.3-3.5 mph (Parise et al. 2004). So there you have it: “Brisk” is an accurate description of a moderate-intensity walk, although the actual pace may vary depending on age and individual fitness level.
3. Does Wearing a Weighted Vest While Walking Burn More Calories?
Weighted vests are gaining attention from exercise professionals and fitness enthusiasts. The vests (typically equal to 5%-20% of a person’s body weight) can be used in many types of workouts, and most vests can be adjusted to add or subtract weight as desired. Further, weighted vests are worn over the shoulders, making them a more natural addition to an exerciser’s center of gravity.
In a 2006 study, Puthoff et al. examined walking energy expenditure at incremental treadmill speeds ranging from 2.0 to 4.0 mph and vest weights ranging from 10% to 20% of body mass. The researchers found that energy expenditure increased as vest weight and walking speed increased; however, the relationship between vest weight and walking speed was not entirely linear. As walking speed increased, wearing a weighted vest had a more pronounced impact on energy expenditure.
These findings have many practical implications in the design of walking programs. For instance, walking at slow speeds may require the exerciser to use a heavier vest to achieve the desired increases in energy expenditure, while walking at faster speeds will produce a more pronounced increase in energy expenditure with less weight needed to generate the increase.
Additionally, walking with a weighted vest may be beneficial for those who cannot walk briskly, as adding just 10% of body mass at a slower walking speed (~2 mph) may produce relative exercise intensity similar to walking faster without added mass.
For answers to several more questions, insights into topics such as inclined treadmill walking, and references, please see “Walking Extravaganza!” in the online IDEA Library or in the October 2013 print edition of IDEA Fitness Journal. If you cannot access the full article and would like to, please contact the IDEA Inspired Service Team at (800) 999-4332, ext. 7, for more information.
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