This is a prospective longitudinal study aiming at investigating the effects of a 12-week exercise program including moderate-intensity walking on depressive symptoms and physical pain in elderly individuals with a good quality of life.

All volunteers were instructed about the study and then signed the consent form. The study was approved and conducted according to the Ethics Committee of the University of Sao Paulo ethical standards (approval number 0562/11) and performed according to the Brazilian National Health Council resolution (196/96).

All patients were recruited from an elderly Community Center in São Paulo, Brazil. Inclusion criteria were: a) medical clearance from the assistant physician for participation in the study; b) age > 60 years; c) > 150 minutes per week of physical activity according to the International Physical Activity Questionnaire (IPAQ) recommendations;23 d) a score between 1 and 7 in the Lequesne algofunctional index for hip and knee osteoarthritis,24 and scores ≥ 40 in the World Health Organization Quality of Life (WHOQOL)-BREF and WHOQOL-OLD questionnaires. Exclusion criteria were absence of one or more evaluations, hormone replacement and/or psychotropic drugs, cardiovascular disease (acute myocardial infarction, stroke, peripheral artery disease and transient ischemic attack), metabolic diseases (type 1 or type 2 diabetes mellitus), pulmonary diseases (emphysema), psychiatric or neurologic diseases (Alzheimer’s or Parkinson’s disease), muscular disorders, skeletal disorders, comorbidities associated with higher risk of falls, clinical diagnosis of diseases associated with physical pain (low back pain) and response rates ≥ 5 in the short form of the Geriatric Depression Scale (GDS).

A total of 165 patients were invited to participate in the study; 96 were excluded: 22 declined to participate, 19 did not answer the invitations, and four had functional impairment. Therefore, 69 volunteers were considered eligible to participate in the study and were randomized by an assistant researcher, using a simple randomization system, a table of random numbers, and categorized in two groups - training group (TG; n = 40) and control group (CG; n = 29) (Figure 1). All volunteers were blinded to the intervention.

Figure 1

All assessments were performed by an investigator who was blinded to the group. Participants were asked to refrain from exercise during the 96 hours before the measurement, and from consuming caffeinated, alcoholic and energy beverages. Although energy intake was not controlled, all volunteers were asked to maintain their usual diet during the study period. No volunteer participated in any other exercise program during the study.

All tests and experimental sessions were carried out at Unifesp Psychobiology Laboratory, under a controlled temperature between 22 and 24º C and relative humidity of 51%. All interviews were in-person and individualized. If the interviewee did not understand the question, the interviewer repeated it slowly, until three times.

The WHOQOL is an instrument recommended to assess the QOL of elderly individuals. This questionnaire is composed of 24 items, organized in six major domains. The values of the six domains or the sum of the 24 questions may be combined to produce an overall score. However, there is no cut-off point, the greater the score, the better the QOL.25

Considering that the WHO recommends that the WHOQOL-OLD should not be administered alone,25 we used the WHOQOL-BREF also. The WHOQOL-BREF is a short version of the WHOQoL-100, used in situations when the time available for application is short and when the number of respondents is large. The WHOQOL-BREF is composed of 26 questions, two of them related to QOL. The questions are organized in four domains: physical, psychological, social relationships and environment, and are positively correlated with the WHOQOL-100 overall score.26

Depressive symptoms were assessed by the short version of the GDS, composed of 15 questions about feelings, and frequency of feelings in relation to life situations. The answers to the GDS questions are based on a binary code: yes or no.27^,28

VAS is a widely used instrument to evaluate pain intensity in different populations, including the elderly. It contains a continuous scale consisting of a 10 cm horizontal line. The respondents place a line perpendicular to the VAS line at the point that represents their pain intensity. Quantification of pain intensity, volunteers were asked about the intensity of physical pain during the last week. A zero (0) means ‘no pain’ and a ten (10) means the worst pain imaginable. VAS score is positively associated with pain intensity.29

Before the cardiac stress test, remained seated for 20 minutes. A resting electrocardiogram was performed to evaluate heart pressure, heart rate and lactate.

Then, incremental test was performed using an electronic treadmill (Life Fitness^®, model 9700HR^®, Fort Mill, Tennessee, USA), according to the modified Bruce protocol, composed of six stages of three minutes each, characterized by both speed (2.7-6.8 km/h) and slope (0-16º) increments.

The gases produced were analyzed during the incremental test using an analyzer (Cosmed^®, Cosmed Quarker CPET^®, Rome, Italy), previously calibrated, with a 3L syringe (flow calibration) and a standard gas mixture containing 4.9% CO₂ and 17.0% O₂ (gas calibration). Ventilation (VE), oxygen consumption (VO₂) and carbon dioxide production (VCO₂) were evaluated in the last 20 minutes of each 3-minute stage.

Heart rate (HR) was continuously measured (Oregon Scientific^®, SE128^®, Portland, Oregon, USA). Peak VO₂ and maximum HR (MaxHR) were recorded at physical exertion of patients.

All volunteers met two criteria for peak VO₂: a) respiratory exchange ratio (RER) ≥ 1.1; b) MaxHR at least equal to 90% of the maximum predicted for age, using the Jones equation (0.65 x age - 210). The electrocardiographic patterns were recorded and analyzed by a cardiologist during all the test.

The intensity, frequency and duration of the aerobic training sessions were conducted according to the ACSM and the American Heart Association (AHA) recommendations. Each participant underwent 36 walking sessions, which occurred three days a week for 12 weeks, with a minimum of 48 hours of recovery between the sessions. Each session consisted of five minutes of warm-up, which involved movements of the whole body; 30 minutes of continuous walking at moderate intensity - 50-70% of MaxHR, established at the stress test previously performed on the treadmill (Life Fitness^®, model 9700HR^®, Fort Mill, Tennessee, USA); finally, 5 minutes of smooth movements, stretching and breathing. A cardiac monitor (Oregon Scientific SE128^®, Portland-Oregon), was used individually, according to the HR of each patient every three minutes in all sessions. Each session was conducted under supervision, which promoted safety and accuracy in prescribing individualized training (50-50% of MaxHR), and if necessary, adjusting for the training zone.

The CG continued their usual activities during the study period, without getting involved in exercise. Patients’ follow-up was conducted by telephone every 15 days to assure that the protocol was being followed.

The Kolmogorov-Smirnov test was used to test data normality. Categorical data were expressed as frequency and percentage, whereas continuous data were described as mean and standard deviation. Between-group comparisons (TG x CG) were made at baseline using the unpaired Student’s t-test. Within-group comparisons (pre-training vs post-training) and intergroup comparisons were conducted by the Split-Plot ANOVA, followed by the Bonferroni low or null correlation; post hoc test. The Pearson correlation coefficients (r) used in the study were: 0 < r < 0.25: low or null correlation; 0.25 < r < 0.50: weak correlation; 0.50 < r < 0.75: moderate correlation; and 0.75 < r < 1.00: strong or perfect correlation. The effect size (ES) was defined as mean Cohen’s d greater than 0.2 and lower than 0.5; values between 0.5 and 0.8 were defined as good ES, and values equal to or greater than 0.8 were defined as a large ES.30 Sample size was calculated considering an alpha error of 5%, statistical power of 90%, and a sample of 80 subjects. The level of significance was set at 5% (p < 0.05) and all analyzes were performed using the Statistical Package for the Social Sciences software, version 20.0. (IBM^®, New York, New York, USA).

Characteristics of the subjects at baseline are described in Table 1. As expected, all volunteers were elderly. Participants in both groups were classified as normal weight or overweight according to the body mass index (BMI) categories. On the other hand, all subjects had a very low to low cardiorespiratory fitness, as compared with the limits established for the elderly population.31 The unpaired Student’s t-test did not show any significant difference between the groups. All volunteers participated in 100% of sessions, and no adverse effect was observed during or after the training sessions.

Primary results are shown in Figures 2 and 3. There was a significant reduction in GDS in the TG after 12 weeks of walking training. In contrast both GDS and VAS remained unchanged in the CG (GDS = 3.0 ± 2.7 to 3.1 ± 2.4; p = 0.94; ES = - 0.03; VAS = 4.4 ± 3.2 to 4.2 ± 3.2; p = 0.68; ES = 0.06).

Figure 2

GDS: geriatric depression scale; TG: training group; CG: control group; p = 0.04* (Student’s t-test)

QOL (WHOQoL-OLD and WHOQoL-BREF) (Figure 4) and cardiorespiratory fitness (Table 2) were assessed as secondary outcomes. Regarding QOL, no difference was seen between the groups (TG [WHOQoL-OLD = 66.5 ± 14.0 % to 65.6 ± 15.9 %, (p = 0.94, ES = 0.06); WHOQoL-BREF = 67.8 ± 11.0 to 69.4 ± 10.8 (p = 0.21, ES = -0.14)] and CG [WHOQoL-OLD = 64.7 ± 12.3 to 63.2 ± 13.4, (p = 0.52, TE = 0.11)]; WHOQoL-BREF = 67.1 ± 10.6 to 64.3 ± 11.9 (p = 0.16, ES = 0.24). Similarly, peak VO₂ did not show significant differences between the groups before and after the training: TG (23.67 ± 5.18 to 24.46 ± 5.62) and CG (23.61 ± 4.86 to 23.57 ± 4.65).

Figure 4

GDS: geriatric depression scale; VAS: visual analogue scale; TG: training group; CG: control group

Figure 5 illustrates the results of the Pearson analysis. There was a positive, moderate correlation between GDS and VAS (r = 0.30; p = 0.05).

Figure 5

GDS: geriatric depression scale; VAS: visual analogue scale; TG: training group; CG: control group

This study has some limitations that should be consider to contribute to a better inference from the data. First, the lack of specific physical examinations (muscle and fat mass) that could lead to a better understanding of the relationship between walking training and QOL, as well as the inclusion of other exercise groups, walking training strategies and exercise protocols.