THE IMPACT OF PHYSICAL FITNESS AND PHYSICAL ACTIVITY LEVEL ON BIOMECHANICAL AND METABOLIC PARAMETERS OF TREADMILL WALKING IN NORMAL-WEIGHT AND OBESE YOUNG ADULTS.

Obesity and physical inactivity are classified as “noncommunicable disease” and causes every year millions of deaths in the world. Walking has been proposed as a valid way to fight against these diseases because it can produce substantial health benefits and also because people can easily perform it every day. AIMS: At first, we assessed if physical activity (PA) or physical fitness (PF) could affect walking economy (Net EC) and efficiency in a group of healthy normal-weight adults, separately for men and women. Secondly, we assessed the same variables in a group of obese young adults. MATERIALS AND METHODS: 30 young normal-weight (14F,16M; 18.5<BMI<25 kg•m-2) and 14 obese (7F,7M; BMI>30 kg•m-2) subjects were recruited in the study. Economy (Net EC) was analyzed with indirect calorimetry and, simultaneously, total mechanical work (Wtot) was assessed with an optoelectronic system at 3.5/ 4.5/ 5.5 km•h-1. Efficiency was calculated as Wtot/Net EC. To assess PA, subjects wore an activity monitor for a whole week, inferring time spent in sedentary (SED, <1.5 METs), or moderate to vigorous (MVPA, >3 METs) physical activity. MVPA were calculated both as overall daily minutes (MVPAall) and also in bouts of at least 10 min (MVPAbouts). To assess PF, a maximal V’O2max test was performed on a treadmill with indirect calorimetry, isometric maximal voluntary contraction (iMVC) of lower limbs was measured by two force plates on horizontal leg press, flexibility (Flex) was assessed by the V-sit and reach test, and % fat mass (%FM) was evaluated with skinfold thickness (in normal-weight) or with girth measurements (in obese subjects). RESULTS: In normal-weight adults, no significant associations, adjusted for age and body mass index, were identified between PA and gait economy or efficiency. Regarding PF, in females iMVC and Flex affected efficiency (R2 = 0.73, F= 12.95, p<0.001), whereas V’O2max and iMVC were associated with economy (R2 = 0.69, F= 15.13, p<0.001). In the obese group, at a speed near the preferred one, SED (with %FM, iMVC and Flex) was positively associated with Net EC (R2 = 0.54, F= 4.04, p<0.05), whereas MVPAall was positively associated with gait efficiency (R2 = 0.32, F= 4.09, p<0.05). CONCLUSIONS: The main findings of this study were that in normal-weight adults PA did not affect neither economy nor efficiency of treadmill walking, whereas in obese individuals SED reduced gait economy and MVPAall enhanced gait efficiency. These findings might to be considered for exercise prescription.