2.1

Participants

Healthy Caucasian postmenopausal women (amenorrhea for at least 12 months), 50 to 65 year-old who were moderately obese (BMI ranging from 29 to 35 kg/m ² ) participated in our study. They had to be sedentary (exercising less than 30 minutes per week), non-smokers, and none or moderate consumers of alcohol and caffeine. Their body weight had to be stable (less than 2 kg weight change) in the year before the onset of the study. All participants were asked to maintain their current lifestyle habits during the study-period. Women had a physical examination by their personal physician, and none of them had any identified cardiomyopathy, endocrine disorders or orthopedic limitations that would limit their participation in physical activity.

2.2

Study design

The study design was approved by the institutional review board of the French Federation of Physical Education and Voluntary Gymnastic (FFEPGV) and the protocol was reviewed and approved by the local Research Ethics Board. All women gave their written informed consent to participate in this study in conformance with the Helsinki Declaration. All participants were asked to maintain their lifestyle habits constant, during the 16-week walking period. Although their daily energy intake remained unchanged, their energy expenditure was slightly increased by 151 ± 24 kcal/day (mean ± SD; P < 0.0001) at the end of our program . Finally, all women were offered a Polar Heart Rate (HR) monitor (FS1 type, Finland) as an incentive to continue walking, and received a personal report on their physical (anthropometry and body composition, physical fitness) and biological (lipid-lipoprotein profile) changes, at the end of the study.

The walking program planned according to the ACSM/AHA guidelines for older adults consisted in 3 non-consecutive sessions/week of 45 min, at approximately 60% of one’s HR reserve, HRR (i.e., maximal HR minus resting HR), during 4 months. Maximal HR was calculated from the following equation: 220 − age, where age is expressed in years. HR walking was calculated as % HRR + resting HR . Two weekly walking sessions were supervised by a trained exercise leader of the FFEPGV. The third weekly unsupervised session was performed according to participants’ preferences on sidewalks, streets, forest trails or in parks.

Subjects’ assiduity was registered in an exercise logbook, and adherence to the program was calculated from the following equation: % of adherence to the program = (number of sessions followed/total number of training sessions) × 100. HR was continuously recorded using a Polar HR monitor at each walking session (either supervised or not) to ensure compliance with the walking intensity. Monitoring HR allowed to control exercise intensity and to document the specific amount of exercise performed during each session. Effective exercise intensity was calculated from the following equation: % of HRR = (mean of exercise HR−resting HR)/(maximal HR−resting HR).

From the 200 postmenopausal women who began our walking program, 159 completed our study. Forty one subjects were not included in the study for the following reasons: injury ( n = 2); illness ( n = 5); did not complete the dietary and physical activity diaries at the end of the walking program as well the exercise log book ( n = 26); and did not perform the 2-km walk test after our intervention ( n = 8). Anthropometry and body composition, physical fitness and fasting lipid-lipoprotein profile were assessed at both the beginning and the end of the 16-week walking program by members of the research team.

2.3

Measurements

2.4

Physical fitness

Physical fitness was assessed by means of the 2-km walking test, which has been validated on moderately fit and obese but otherwise healthy, men and women aged 20–65 years . Physical fitness was more accurately predicted in women than in men, as it underestimates O ₂ max by 3% in the former vs 12.4% in the latter individuals. The equation used to predict V ˙ O 2 max in women was the following: V ˙ O 2 max (mL O ₂ /kg/min) = 116.2−2.98 (time)−0.11 (HR)−0.14 (age)−0.39 (BMI) where time is the elapsed time for a walk in min, HR is the value at the end of the walk (beats/min) and age is expressed in years and BMI in kg/m ² . Physical fitness measurements were performed by the same FFEPGV exercise leaders, at both study periods .

2.5

Lipid-lipoprotein profile

Blood samples were collected after a 12-h overnight fast, at both study periods. Fasting plasma triglyceride (TG), cholesterol, and High-Density Lipoprotein (HDL) cholesterol levels were routinely determined according to standardized laboratory procedures. Fasting plasma Low-Density Lipoprotein (LDL) cholesterol concentrations were estimated by the Friedewald equation (1972) .

2.6

Statistical analyses

Results are given as means ± standard error (SE) in figures and as means ± standard deviation (SD) in tables. To analyze the impact of the inter-individual variability on the body composition and lipid-lipoprotein profile changes, tertiles of adherence and exercise intensity were performed a posteriori. The first tertile of adherence was lower than 71% (i.e., < 96 minutes of walking/week), while the second ranged between 71% and 87% (i.e., between 96 and 117 minutes of walking/week) and the third was higher than 87% (i.e., > 117 minutes of walking/week). On the other hand, the first tertile of walking intensity was lower than 56% of HRR, while the second ranged between 56% and 63% of HRR and the third one was higher than 63% of HRR. Basal values and mean changes (i.e., differences between post- and pre-training values) for the outcome variables of this study were compared between three groups of women categorized as having a low, medium vs high adherence, using an analysis of variance (ANOVA) with repeated measures on one factor (time). When ANOVA was significant, simple test effects were performed to detect which conditions were statistically different from each other. All analyses were conducted using the SAS statistical software (SAS Institute, version 9.1, Cary, NC, USA), and statistical significance was set at P ≤ 0.05.

2.1

Participants

Healthy Caucasian postmenopausal women (amenorrhea for at least 12 months), 50 to 65 year-old who were moderately obese (BMI ranging from 29 to 35 kg/m ² ) participated in our study. They had to be sedentary (exercising less than 30 minutes per week), non-smokers, and none or moderate consumers of alcohol and caffeine. Their body weight had to be stable (less than 2 kg weight change) in the year before the onset of the study. All participants were asked to maintain their current lifestyle habits during the study-period. Women had a physical examination by their personal physician, and none of them had any identified cardiomyopathy, endocrine disorders or orthopedic limitations that would limit their participation in physical activity.

2.2

Study design

The study design was approved by the institutional review board of the French Federation of Physical Education and Voluntary Gymnastic (FFEPGV) and the protocol was reviewed and approved by the local Research Ethics Board. All women gave their written informed consent to participate in this study in conformance with the Helsinki Declaration. All participants were asked to maintain their lifestyle habits constant, during the 16-week walking period. Although their daily energy intake remained unchanged, their energy expenditure was slightly increased by 151 ± 24 kcal/day (mean ± SD; P < 0.0001) at the end of our program . Finally, all women were offered a Polar Heart Rate (HR) monitor (FS1 type, Finland) as an incentive to continue walking, and received a personal report on their physical (anthropometry and body composition, physical fitness) and biological (lipid-lipoprotein profile) changes, at the end of the study.

The walking program planned according to the ACSM/AHA guidelines for older adults consisted in 3 non-consecutive sessions/week of 45 min, at approximately 60% of one’s HR reserve, HRR (i.e., maximal HR minus resting HR), during 4 months. Maximal HR was calculated from the following equation: 220 − age, where age is expressed in years. HR walking was calculated as % HRR + resting HR . Two weekly walking sessions were supervised by a trained exercise leader of the FFEPGV. The third weekly unsupervised session was performed according to participants’ preferences on sidewalks, streets, forest trails or in parks.

Subjects’ assiduity was registered in an exercise logbook, and adherence to the program was calculated from the following equation: % of adherence to the program = (number of sessions followed/total number of training sessions) × 100. HR was continuously recorded using a Polar HR monitor at each walking session (either supervised or not) to ensure compliance with the walking intensity. Monitoring HR allowed to control exercise intensity and to document the specific amount of exercise performed during each session. Effective exercise intensity was calculated from the following equation: % of HRR = (mean of exercise HR−resting HR)/(maximal HR−resting HR).

From the 200 postmenopausal women who began our walking program, 159 completed our study. Forty one subjects were not included in the study for the following reasons: injury ( n = 2); illness ( n = 5); did not complete the dietary and physical activity diaries at the end of the walking program as well the exercise log book ( n = 26); and did not perform the 2-km walk test after our intervention ( n = 8). Anthropometry and body composition, physical fitness and fasting lipid-lipoprotein profile were assessed at both the beginning and the end of the 16-week walking program by members of the research team.

2.3

Measurements

2.4

Physical fitness

Physical fitness was assessed by means of the 2-km walking test, which has been validated on moderately fit and obese but otherwise healthy, men and women aged 20–65 years . Physical fitness was more accurately predicted in women than in men, as it underestimates O ₂ max by 3% in the former vs 12.4% in the latter individuals. The equation used to predict V ˙ O 2 max in women was the following: V ˙ O 2 max (mL O ₂ /kg/min) = 116.2−2.98 (time)−0.11 (HR)−0.14 (age)−0.39 (BMI) where time is the elapsed time for a walk in min, HR is the value at the end of the walk (beats/min) and age is expressed in years and BMI in kg/m ² . Physical fitness measurements were performed by the same FFEPGV exercise leaders, at both study periods .

2.5

Lipid-lipoprotein profile

Blood samples were collected after a 12-h overnight fast, at both study periods. Fasting plasma triglyceride (TG), cholesterol, and High-Density Lipoprotein (HDL) cholesterol levels were routinely determined according to standardized laboratory procedures. Fasting plasma Low-Density Lipoprotein (LDL) cholesterol concentrations were estimated by the Friedewald equation (1972) .

2.6

Statistical analyses

Results are given as means ± standard error (SE) in figures and as means ± standard deviation (SD) in tables. To analyze the impact of the inter-individual variability on the body composition and lipid-lipoprotein profile changes, tertiles of adherence and exercise intensity were performed a posteriori. The first tertile of adherence was lower than 71% (i.e., < 96 minutes of walking/week), while the second ranged between 71% and 87% (i.e., between 96 and 117 minutes of walking/week) and the third was higher than 87% (i.e., > 117 minutes of walking/week). On the other hand, the first tertile of walking intensity was lower than 56% of HRR, while the second ranged between 56% and 63% of HRR and the third one was higher than 63% of HRR. Basal values and mean changes (i.e., differences between post- and pre-training values) for the outcome variables of this study were compared between three groups of women categorized as having a low, medium vs high adherence, using an analysis of variance (ANOVA) with repeated measures on one factor (time). When ANOVA was significant, simple test effects were performed to detect which conditions were statistically different from each other. All analyses were conducted using the SAS statistical software (SAS Institute, version 9.1, Cary, NC, USA), and statistical significance was set at P ≤ 0.05.