Influence of Muscle Strength on the Energy Cost of Walking in Obese Subjects

Background: in Reunion Island in 2000, the REDIA study showed a prevalence of obesity among women and men of 20% and 10%, respectively. Obesity is associated with several diseases, including diabetes mellitus, hypertension, dyslipidaemia and ischaemic heart diseases. Regular physical activity associated with a hypocaloric diet and an intake of fruits and vegetables can reduce body fat mass and obesity-associated complications. However there is no consensus on the physical training protocols for prevention and treatment of obesity. As a consequence, future studies are required to improve obesity management and decrease obesity-associated complications.

Main objective: to compare the effects of two programs of rehabilitation training associated with a diet supplemented with fruits and vegetables on reducing energy cost of walking in obese adults.

Secondary objectives: to compare the effects of two programs of rehabilitation training associated with a diet supplemented with fruits and vegetables on:

• the mechanical properties of the lower extremity muscles,
• the biomechanics of walking,
• the walking intensity,
• body composition,
• the quality of life, and physical activities compliance and motivation,
• the alimentary behaviour,
• and the oxidative stress and the inflammatory status.

Abstract:

Regular physical activity associated with a hypocaloric diet and an intake of fruits and vegetables can reduce body fat mass and prevent the inflammatory and oxidative stress which are associated with obesity. Daily physical activities such as carrying bags, making housework, stair climbing, or simply walking, are recommended to increase total daily energy expenditure. However, obese individuals have a higher energy cost of walking compared with their lean counterparts. This higher energy cost of walking does not induce higher total daily energy expenditure by an increase in activity energy expenditure, but inversely, increases exercise intensity and reduces walking practice. It has been shown that this higher energy cost of walking could be due to reduced lower extremity muscle strength of obese individuals. Moreover, muscle strength is also reduced after a weight loss due to a decrease in lean body mass. However, it has been shown in lean and over-weight individuals, that strength training could induce a decrease of the energy cost of walking, making easier walking activities.

Thus, we propose in obese patients to compare the short- and medium-term results of two training protocols for 5 months, both associated with a diet supplemented with fruits and vegetables, on reducing energy cost of walking. The study will last 9 months in total with a 5 months training period.

Participants will be randomized into 2 arms: arm 1 will consist of an interval strength training for 30 min on bicycle ergometer (which include strengthening exercises in an high intensity interval training), and arm 2 will consist of a isocaloric continuous exercise realised at moderate intensity (50 % of Vo2max) for 40 min on bicycle ergometer too. Participants will meet for training three times per week for 5 months under supervision of an exercise physiologist. All the participants will have an initial nutritional education session at the beginning of the study and will answer to questionnaires on training experience during the 5 months training period (Exercise difficulties, pain...).

At the beginning of the study and at each follow-up visit (5th and 9th month), all participants will have:

• biological analysis : blood glucose, HbA1c, insulin, cholesterol total, HDL, LDL, triglycerides, C reactive protein (CRP), albumin, creatinine, urinary parameters, antioxidant status, inflammatory markers,
• maximal cardiopulmonary exercise,
• anthropometric and functional examinations : weight, height, waist, hip and thigh circumferences, blood pressure and body composition assessed by dual x-ray absorptiometry,
• laboratory tests : measurements of energy cost of walking, walking pattern on treadmill, and muscle strength,
• questionnaires on quality of life, alimentary behaviour, experience of physical activities and on physical activities compliance and motivation.

Inclusion criteria

• Men and women
• 18-40 years old
• 30 ≤ BMI ≤40 kg / m²
• sedentary
• considered clinically stable
• able to rehabilitation training
• having signed an informed consent
• without professional activity

Exclusion criteria

• blood glucose ≥ 1.26 g / l
• HbA1c ≥ 6.5%
• severe hypertension (Systolic Blood Pressure (SBP) ≥ 180 mmHg and / or Diastolic Blood Pressure (DBP) ≥ 110 mmHg)
• hypertension (≥140/90 mmHg) untreated or treated by beta blocker or calcium blocker
• absolute and relative contraindication to the maximal exercise test (ACC / American Heart Association 2002) and / or physical training
• inability to achieve the maximum exercise test and / or the metabolic exercise test by indirect calorimeter
• uncompensated cardiovascular and / or respiratory disease revealed by exercise test
• pacemaker or defibrillator
• recent cardiovascular events (heart failure, treated by positive inotropic drugs, angioplasty within the last 10 days, cardiac surgery within the last 3 months, valvular disease requiring surgical correction, evolving myopericarditis, severe ventricular arrhythmias non stabilized under treatment)
• known and documented myopathy
• cancer
• acute and chronic inflammatory disease
• end stage renal disease
• digestive system operation
• treated by corticoids, thyroid hormone, antidepressant or neuroleptics
• pregnancy
• mental deficiency that prevents the understanding of informed consent and protocol
• participation to another research protocol
• attendance in the previous month to a program of rehabilitation training or a diet
• associated evolutionary disease causing significant impairment of general condition.