Effects of age and physical activity status on the speed-aerobic demand relationship of walking

Abstract

Older adults tend to show lower preferred walking speeds and higher aerobic demands per distance walked than young adults. It has been suggested that a more sedentary life-style contributes to diminished musculoskeletal functioning, which in turn contributes to poorer economy of motion in the aged and sedentary adults. The purpose of this study was to quantify the speed-aerobic demand relationship during walking for old (greater than 65 yr of age) and young adults and to determine whether physical activity status affects this relationship. Aerobic demands for 30 young and 30 old individuals representing sedentary and physically active groups were measured as the subjects performed treadmill walking at seven speeds ranging from 0.67 to 2.01 m/s. All four age/physical activity groups displayed U-shaped speed-aerobic demand curves with minimum gross oxygen consumption per unit distance walked (ml.kg-1.km-1) at 1.34 m/s. A statistically significant age effect on walking aerobic demand was observed, with old subjects showing an 8% higher mean aerobic demand than the young subjects. This age-related effect was not associated with shifts in the speed at which aerobic demand was minimized or with the preferred walking speed of older individuals falling on a less economical portion of the speed-aerobic demand curve. Rather, it was speculated that declines in force-generating capacity of muscle in the aged may require recruitment of additional motor units and perhaps an additional proportion of less economical fast twitch muscle fibers to generate necessary forces. Physical activity status had no significant effect on walking aerobic demand.(ABSTRACT TRUNCATED AT 250 WORDS)

The improvement of walking speed after cardiac rehabilitation is associated with the reduction in the metabolic cost of walking in older persons

“…As our patients, according to the recommendations of the American Thoracic Society [15], performed the 6mWT over ground at their individually selected maximal speed, for each patient we were able to assess only one point of the speed-metabolic demand curve before and after the rehabilitation. Thus, we do not know whether the physical training component of our cardiac rehabilitation program has actually shifted the whole curve downward [5] or whether the decrease of the energy cost of walking was accounted for simply by a shift away from an uneconomical towards a more economical region of the same speed-metabolic demand curve [21].…”

“…First, in terms of kinematics, walking speed and metabolic demand are related to each other according to a U-shaped curve, whose central region is the region in which the metabolic cost of walking is minimized [3,5]. As our patients, according to the recommendations of the American Thoracic Society [15], performed the 6mWT over ground at their individually selected maximal speed, for each patient we were able to assess only one point of the speed-metabolic demand curve before and after the rehabilitation.…”

“…Finally, as aging is associated with a progressive loss of muscle mass and strength [30], to perform a given task older persons likely have to recruit more motor units or to increase the level of activation of already recruited muscle fibres, both of which are detrimental to muscle efficiency [21]. So, the greater cost of generating muscle force has also been proposed as a potential mechanism for the agerelated increase of the metabolic cost of walking [5,24,25]. However, even in this case, the two studies that addressed this issue reported conflicting results.…”

“…However, the preferred speed of walking tends to decline with advancing age and to walk a given distance older persons consume more metabolic energy than younger adults across all speeds [3][4][5].…”

Effect of upper extremity swing restrain on walking energy consumption and balance

“…[11] Yürüme sırasında tercih edilen yürüme hızı ve yürümenin oksijen maliyeti, yürümeyi genel olarak değerlendiren ve patolojik ile normal yürümeyi birbirinden ayırt etmemizi sağlayan önemli iki parametredir. [12,13] Yürüme oksijen maliyeti belirli bir mesafeyi (örneğin 1 metre) kat etmek için harcanan oksijen miktarıdır [14] ve bu ölçüm yapılarak yürüme sırasında kullanılan enerjinin verimliliği de hesaplanabilir. [12] Vücut kütle merkezi (VKM) ise vücut kütlesi bütü-nünün tek bir noktada dengede olduğu kabul edilen hayali bir nokta olarak tanımlanabilir.…”