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Short-term program of aerobic training prescribed using critical velocity is effective to improve metabolic profile in postmenopausal women
Science & Sports (2016) 31, 95—102
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ORIGINAL ARTICLE
Short-term program of aerobic training prescribed using critical velocity is effective to improve metabolic profile in postmenopausal women Un programme de court terme d’entraînement aérobique prescrit en utilisant la vitesse critique est efficace pour améliorer le profil métabolique chez les femmes ménopausées T.A. Diniz a,b,∗, A.C.S. Fortaleza a, F.E. Rossi a,b, L.M. Neves a, E.Z. Campos b, I.F. Freitas Junior a a
Center of Studies and Laboratory of Evaluation and Prescription of Motor Activities (CELAPAM), Department of Physical Education, Sao Paulo State University (UNESP), Rua Roberto Simonsen, 305, 19060-900, Presidente Prudente, SP, Brazil b Exercise and Immunometabolism Research Group, Department of Physical Education, Sao Paulo State University (UNESP), 19060-900, Presidente Prudente, SP, Brazil Received 14 February 2015; accepted 23 March 2015 Available online 2 December 2015
KEYWORDS Endurance training; Lipoproteins; Obesity; Menopausal women
∗
Summary Purpose. — The aim of this study was to verify the effectiveness of an eight-week aerobic training prescribed by the critical velocity on metabolic profile. Methods. — The participants were divided into two groups: Aerobic Training (AT [n = 10]) and Control group (CG [n = 9]). Aerobic intensity was prescribed using critical velocity and the women exercised during eight weeks. The trunk body fat (TBF), body fat (BF) and fat-free mass were estimated using DXA. The total cholesterol (TC), low-density lipoprotein (LDL-c), high-density lipoprotein (HDL-c), triacylglycerol and glucose were analyzed in a particular laboratory. Results. — After eight weeks, there were statistically significant differences between AT and CG in TBF (CG = 4.27 ± 5.10 vs. AT = −3.13 ± 4.65; P = 0.006), BF in kg (CG = 2.79 ± 5.91 vs. AT = −2.75 ± 3.01; P = 0.015) and percentage (CG = 1.83 ± 3.67 vs. AT = −2.40 ± 2.67; P = 0.010), LDL-c levels (CG = 10.95 ± 23.63 vs. AT = −11.96 ± 22.00; P = 0.045) and a tendency in TC (GC = 9.00 ± 15.59 vs. AT = −6.67 ± 16.43; P = 0.052).
Corresponding author. E-mail address: [email protected] (T.A. Diniz).
http://dx.doi.org/10.1016/j.scispo.2015.03.006 0765-1597/© 2015 Elsevier Masson SAS. All rights reserved.
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T.A. Diniz et al. Conclusion. — In summary, the present study suggests that even a short-term of aerobic training, prescribed using critical velocity, is effective in decreasing whole body fat, central adiposity and low-density lipoprotein-cholesterol in postmenopausal women. © 2015 Elsevier Masson SAS. All rights reserved.
MOTS CLÉS Entraînement d’endurance ; Lipoprotéines ; Obésité ; Femmes ménopausées
Résumé But. — Le but de cette étude était de vérifier l’efficacité d’un entraînement aérobique de huit semaines prescrit à la vitesse critique du profil métabolique. Méthodes. — Les participants ont été divisés en deux groupes : entraînement aérobique (AT [n = 10]) et groupe de témoin (CG [n = 9]). Des exercices d’aérobique d’intensité ont été prescrits en utilisant la vitesse critique et des exercices pour les femmes pendant huit semaines. La graisse du corps de tronc (TBF), la graisse corporelle (BF) et la masse maigre ont été estimées en utilisant la méthode DXA. Le taux de cholestérol total (TC), la lipoprotéine de basse densité (LDL-c), les lipoprotéines de haute densité (HDL-c), triglycérides et glucose ont été analysés dans un laboratoire particulier. Résultats. — Après huit semaines, il y avait une différence statistiquement significative entre AT et CG dans la TBF (CG = 4,27 ± 5,10 vs −3,13 ± AT = 4,65 ; p = 0,006), BF en kg (GC = 2,79 ± 5,91 vs −2,75 ± AT = 3,01 ; p = 0,015) et le pourcentage (GC = 1,83 ± 3,67 vs AT = −2,40 ± 2,67 ; p = 0,010), niveaux de LDL-c (GC = 10,95 ± 23,63 vs AT = −11,96 ± 22,00 ; p = 0,045) et une tendance en TC (GC = 9,00 ± 15,59 vs −6,67 ± AT = 16,43 ; p = 0,052). Conclusion. — En résumé, la présente étude suggère que même une courte période d’entraînement aérobique, prescrite en utilisant la vitesse critique, est efficace pour réduire la graisse sur tout le corps, l’adiposité centrale, le cholestérol total et le cholestérol de lipoprotéines de basse densité chez les femmes postménopausées. © 2015 Elsevier Masson SAS. Tous droits réservés.
1. Introduction The postmenopausal period is strictly defined by the World Health Organization (WHO) as the permanent cessation of menstruation (12 months of uninterrupted amenorrhea) occurring naturally, by surgery, chemotherapy or radiation, followed by the loss of ovarian activity and leading to decreased secretion of sex hormones, especially estrogen and progesterone [1]. The downregulation in the estrogen’s secretion is related to an increase in the lipogenic genes and the decrease in the lipolytic genes in various tissues, especially in adipose [2,3]. In addition, these women also present low levels of progesterone, which acts as a glucocorticoid receptor antagonist. Glucocorticoids are known for promoting the accumulation of fat in the abdominal region [4]. These postmenopausal events, when associated with unhealthy behaviors such as physical inactivity and inadequate diet, increase the likelihood of these women becoming obese [5,6]. It is well known that obesity is an independent risk factor in the development of several chronic diseases, such as insulin resistance, atherosclerosis and dyslipidemias [7—9], which together contributes to increase the leading cause of death in women, coronary heart disease [10]. Thus, strategies that aim to promote body fat (BF) loss seem promising for these women. The most common physical activity in the elderly is walking/running [11,12]. However, the studies that aimed to assess the effect of walking or running on the metabolic profile in postmenopausal women used mostly invasive, laboratorial and/or high cost
methods to evaluate and determine the intensity of exercise, or only used the rating of perceived exertion without a specific intensity of training, precluding its use in practice [13—15]. In this way, an alternative method used by our laboratory to determine the anaerobic threshold intensity in walking exercise is critical velocity (CV) [16]. CV has its origin in critical power, which was defined as the slope regression line based on the total work done and the corresponding time until exhaustion [17]. Given the critical power model needed to reach the level of exhaustion, Wakayoshi et al. [18] have proposed a new model to determine CV through determination of the time needed to cover a certain distance. Although the last study used swimming as their chosen modality, this protocol was already validated in track running [19]. In addition to the CV being considered a tool to estimate the individual’s aerobic capacity (i.e. maximal lactate steady state), it can also be used for prescribing training. The total energy expenditure is an important consideration in weight loss programs [20]. Therefore, since anaerobic threshold is the boundary between aerobic and anaerobic metabolism, it allows a long-term training (e.g. 35 to 50 min) and shows a high-energy expenditure during and postexercise when compared with low effort intensities [21]. Moreover, the training above the CV (i.e. above anaerobic threshold) would increase the anaerobic metabolism, reducing the fat oxidation during exercise; furthermore, this intensity would turn the exercise an unpleasant activity [22]. However, it still needs to be elucidated whether the CV (evaluated by the distance × time relation) is a useful
Aerobic training prescribed using critical velocity and postmenopausal women method for training prescription for postmenopausal women aiming to improve their metabolic profiles. Thus, the aim of this study was to verify the effectiveness of eight-weeks of aerobic training determined by the CV on body composition (whole and central adiposity), lipid and glycemic profile in postmenopausal women.
2. Materials and methods 2.1. Participants Subjects were invited through television and newspaper advertising to participate in the study. The participants contacted the researchers by phone and an appointment was made in order to carry out a more detailed interview. All measurements were taken at the University Laboratory. The inclusion criteria were: • being in menopause (having had no menstrual cycle for at least one year and a follicle stimulating hormone (FSH) level of 30 U/L or greater) [1]; • not presenting any physical limitations or health problems that could prevent the completion of the assessments and exercise intervention; • presenting a medical certificate to participate in the training; • not having engaged in any systematic physical exercise (i.e.: walking/running, resistance and swimming training, etc.) for at least six months prior to the study; • not receiving treatment for hormone replacement; • signing the consent form. Out of a total of 40 women who participated in the first screening, 31 met all the inclusion criteria and agreed to participate in the study protocol. Moreover, in this study, we excluded the women who were diabetic and hypercholesterolemic (n = 7). Participants were divided into aerobic training (n = 12) and control groups (n = 12) randomly using a method based on block randomization, which consisted of one block (random sequence), of 24 participants, and an allocation ratio of 1:1. The block was composed of 12 women of each group. During the eight weeks of training, five of the 24 women dropped out of the study. The reasons for dropouts included minor injuries; personal/family problems; unspecified reasons; and the accumulation of three consecutive absences or four nonconsecutive absences during one month. The final sample was composed of 19 subjects: aerobic training (n = 10) and control group (n = 9). All procedures used in this study met the criteria of the Ethics in Human Research according to no. 196/96 of the National Health Council - Brasilia - DF. All participants included in the study signed an informed consent approved by the Ethics in Research Committee from the university linked to the project (Protocol: 64/2011).
2.2. Methods This intervention study was carried out from February to July of 2013 at Sao Paulo State University (UNESP), Presidente Prudente, Brazil. The initial assessment occurred two weeks before the baseline moment (M0) and, consisted of
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the anamnesis to verify whether the participants met the inclusion criteria. At this time, anthropometry and body composition were evaluated. After eight-weeks of intervention, all measurements were repeated (M8). The training group performed eight weeks of aerobic training and the control group maintained a sedentary lifestyle for 8 weeks, without participating in any regular physical exercise. Both groups were asked to maintain the pattern of nutrition intakes. All measurements were made by trained evaluators who are studying physical education at UNESP, and the training seasons were always supervised by graduate students and physical education students.
2.3. Anthropometric measurements and body composition Before the anthropometric evaluation, the female study participants were requested to attend the evaluation day barefoot and wearing light clothing. Anthropometry was composed of body weight and height measurements. Height was measured on a Sanny brand fixed stadiometer, with an accuracy of 0.1 cm and length of 2.20 m. Body weight was measured using an electronic scale (Filizola PL 50, Filizzola Ltda., Brasil), with a precision of 0.1 kg. The body composition was estimated using a DXA scanner, version 4.7 (General Electric Healthcare, Lunar DPX-NT; England). The subjects were positioned in a supine position and remained immobile throughout the examination. Total BF in percentage and kilograms, fat located in the trunk region (TBF), and fat-free mass (FFM) were assessed and expressed in absolute and relative values by the DEXA software. The TBF was estimated in the abdominal region, and was defined as 20% of the length from a circumference line at the pelvis to a circumference line at the neck. All measurements were carried out at the University Laboratory in a temperature-controlled room. Each morning, before the beginning of the measurements, the equipment was calibrated by the same researcher, according to the manufacturer’s instructions.
2.4. Blood samples After an overnight fast (12 h), venous blood samples were collected to measure glucose, triglycerides (TG), fasting total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c) and low-density lipoprotein cholesterol (LDL-c), using the colorimetric technique in dry chemical and Johnson and Johnson equipment, model Vitros 250. The Friedewald et al. [23] formula was used to calculate the LDL-c concentration.
2.5. Aerobic training protocol The determination of the intensity of the aerobic training was performed using the CV protocol proposed by Wakayoshi et al. [18]. The aerobic training group travelled three distances (400, 800 and 1200 m) on a running track on separate, nonconsecutive, days. The participants were instructed to cover the distance in the shortest possible time, which was recorded using a digital stopwatch (Polar® ).
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Figure 1 Example of a subject relation between distance performed and time to complete, and linear regression. Critical velocity was assumed as the angular coefficient of the relation (i.e. 1.44 m·s−1 ).
A linear regression was obtained by the relation between distance (meters) and time (seconds). The CV was assumed by the angular coefficient of linear regression straight line between the distances and the respective times obtained in each repetition [18] (Fig. 1). Before the beginning of the training, the participants performed two weeks of familiarization, which consisted of walking, gradually, until reach the volume of the training (50 min). The training volume was equivalent to 50 min/day at 100% of CV. Each exercise session included a 5- to 10-min warm-up and a 5- to 10-min cool down. After four weeks, the procedures of CV were repeated to determine and adjust the intensities to next four weeks of training. Participants were instructed to drink water and wear appropriate shoes and clothing during training. The rating of perceived exertion was determined at the end of each session [24].
2.6. Statistical analysis The data normality was verified using the Shapiro-Wilk test. The descriptive analyses consisted of the mean and standard deviations. Initially, in order to identify the homogeneity of both groups at baseline (basic assumption), dependent variables were compared between the control group and aerobic training group using the Student t test for independent samples. In the longitudinal analysis, the comparison of the metabolic profile between the two groups was conducted by repeated measurements analyses and the differences were calculated by the ‘‘mean percentage differences’’ ([Final Moment—Baseline moment]/Baseline moment * 100), also performing a two-way repeated measure of ANOVA (group × time). When a significant difference in group or interaction was observed, the Tukey post hoc test was conducted. For all measured variables, the estimated sphericity was verified according to Mauchly’s W test, and the Greenhouse—Geisser correction was used when necessary. The effect size was calculated using Eta-square test.
T.A. Diniz et al.
Figure 2 Mean and individual changes in the critical velocity (angular coefficient) pre and post eight-weeks of aerobic training.
All analyses were performed using the statistical software SPSS (version 13.0). The level of significance was set at 5%.
3. Results The sample’s mean age was 61.5 ± 7.4 years and the average percentage of BF was 42.8 ± 5.2. No significance difference was found between the variables of body composition, anthropometric, and age at the first moment (Table 1), thus, indicating that the groups were homogenous. The linear regression of the relation distance vs. time for the CV determinant presented a determinant coefficient of 0.98 ± 0.02 and 0.99 ± 0.00, before and after 8 weeks of training, respectively. Fig. 2 shows group and individual changes in the CV after eight weeks of aerobic training. The CV increased significantly after 8 weeks of aerobic training (5.32 ± 0.70 km·h−1 and 6.43 ± 0.90 km·h−1 ; P < 0.001). Tables 2 and 3 present the relative changes in metabolic profile after eight weeks of aerobic training. The women who were engaged in the intervention decreased their total BF, both absolute and by percentage. When comparing the control and aerobic group, the latter showed a statistically significant decrease in the fat located in the trunk region (kg), total BF (kg), LDL-c and a tendency in total cholesterol. Moreover, the LDL/HDL ratio decreased more than 16 percent in the exercise group, although it was not statistically significant (P = 0.080).
4. Discussion The aim of the present study was to evaluate the effectiveness of aerobic training as determined by the CV in the body composition and metabolic parameters of postmenopausal women. The main findings of the present study were that training eight weeks in the CV was effective in reducing the total and trunk BF, LDL, and TC concentration. Moreover, CV is promising to determine and prescribe the aerobic training intensity for postmenopausal women. Aerobic training has been presented as a nonpharmacological treatment to prevent metabolic and cardiac
Aerobic training prescribed using critical velocity and postmenopausal women
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Table 1 Comparison between the control and aerobic group in the variables of anthropometric, body composition and metabolic profile at the first moment. Variables
Control (n = 9)
Age (years) Weight (kg) BMI (kg/m2 ) TBF (kg) BF (kg) BF (%) FFM (kg) Glucose (mg/dL) Triacylglycerol (mg/dL) Cholesterol (mg/dL) HDL-c (mg/dL) LDL-c (mg/dL) LDL/HDL ratio
62.01 61.51 25.76 13.49 26.09 42.02 33.33 91.22 125.11 190.44 51.11 113.89 2.23
± ± ± ± ± ± ± ± ± ± ± ± ±
Aerobic (n = 10)
7.83 7.68 2.93 2.63 5.74 4.94 3.20 9.19 51.50 34.73 8.57 25.77 0.32
60.26 62.67 25.82 14.27 26.91 42.47 33.48 84.90 92.80 203.60 60.00 125.00 2.21
± ± ± ± ± ± ± ± ± ± ± ± ±
P-value
8.51 7.87 2.74 2.96 6.48 5.89 3.05 4.72 32.22 35.18 12.70 34.86 0.93
0.649 0.749 0.961 0.555 0.774 0.859 0.916 0.072 0.116 0.424 0.095 0.445 0.942
BF: fat in the trunk region; BF: total body fat; FFM: fat-free mass; HDL-c: high-density lipoprotein-cholesterol; LDL-c: low-density lipoprotein-cholesterol; LDL/HDL: Atherogenic index. Values were express in mean and standard deviation.
dysfunction on a wide range of subjects, especially in obese, elderly, and type 2 diabetes patients [25]. However, to ensure beneficial results from aerobic training, the training intensity should be prescribed individually (i.e. anaerobic threshold) [26], and not on a wide range of intensities (i.e. 60—85% of maximal HR), that might elicit different relatives anaerobic threshold intensities [27]. Even though a large number of tests are available to describe aerobic training,
Table 2
they are usually maximal (to exhaustion) and invasive, being difficult to apply in older subjects. Recently, Rossi et al. [28] have tested the reliability and validation of a nonexhaustive CV test to estimate the maximal lactate steady state (MLSS) in postmenopausal women, and found that the test cannot be used to estimate the aerobic capacity. In the present study, the distance vs. time relation during the CV test presented a determinant coefficient of
Characteristics of subjects before and after the exercise program on the body composition.
Variables
Control (n = 9) Mean ± SD
Aerobic (n = 10) Mean ± SD % 0.91 ± 2.73
% −0.76 ± 2.23
Anova
F
P
Time Group Interaction
0.038 0.028 2.541
0.848 0.869 0.129
Weight (Kg) Pretraining Post-training Effect size
61.51 ± 7.68 62.13 ± 8.39 0.13
TBF (kg) Pretraining Post-training Effect size
13.49 ± 2.63 14.13 ± 3.13 0.44
4.27 ± 5.10
14.27 ± 2.96 13.87 ± 3.20 0.27
−2.75 ± 3.01
Time Group Interaction
0.551 0.037 9.818
0.468 0.85 0.006
BF (Kg) Pretraining Post-training Effect size
26.09 ± 5.74 26.95 ± 6.71 0.25
2.79 ± 5.91
26.91 ± 6.48 26.23 ± 6.66 0.45
−2.75 ± 3.01
Time Group Interaction
0.109 0 7.335
0.745 0.985 0.015
BF (%) Pretraining Post-training Effect size
42.02 ± 4.94 42.84 ± 5.72 0.24
1.83 ± 3.67
42.47 ± 5.89 41.47 ± 6.04 0.43
−2.40 ± 2.67
Time Group Interaction
0.082 0.031 8.392
0.778 0.861 0.01
FFM (Kg) Pretraining Post-training Effect size
33.33 ± 3.20 33.06 ± 3.07 0.1
−0.75 ± 2.36
33.48 ± 3.05 33.64 ± 2.61 0.03
0.61 ± 2.99
Time Group Interaction
0.069 0.072 1.001
0.795 0.791 0.331
62.67 ± 7.87 62.18 ± 7.79 0.13
%: relative changes; TBF: fat in the trunk region; BF: total body fat; FFM: fat-free mass; TG: triacylglycerol; TC: cholesterol; HDL-c: high density lipoprotein-cholesterol; LDL-c: low density lipoprotein-cholesterol; LDL/HDL: Atherogenic index. Values were express in mean and standard deviation.
100 Table 3
T.A. Diniz et al. Characteristics of subjects before and after the exercise program on the lipid profile.
Variables
Control (n = 9) Mean ± SD
Aerobic (n = 10) Mean ± SD % −1.38 ± 12.51
Anova
F
P
Time Group Interaction
0.451 5.253 0.172
0.511 0.035 0.684
3.41 ± 24.65
Time Group Interaction
0 4.475 0.003
0.998 0.049 0.955
−6.67 ± 16.43
Time Group Interaction
0.001 0.015 4.366
0.977 0.905 0.052
5.06 ± 11.00
Time Group Interaction
5.106 2.794 0.216
0.037 0.113 0.648
% −0.54 ± 6.54
Glucose (mg/dl) Pretraining Post-training Effect size
91.22 ± 9.19 89.11 ± 5.78 0.04
TG (mg/dl) Pretraining Post-training Effect size
125.11 ± 51.50 124.67 ± 30.62 0.01
13.97 ± 60.86
92.80 ± 32.22 93.20 ± 28.79 0.01
TC (mg/dl) Pretraining Post-training Effect size
190.44 ± 34.73 205.22 ± 34.27 0.25
9.00 ± 15.59
203.60 ± 35.18 188.40 ± 41.15 0.18
HDL-c (mg/dl) Pretraining Post-training Effect size
51.11 ± 8.57 55.67 ± 7.50 0.24
11.05 ± 20.37
60.00 ± 12.70 63.00 ± 13.96 0.22
LDL-c (mg/dl) Pretraining Post-training Effect size
113.89 ± 25.77 124.56 ± 30.75 0.16
10.95 ± 23.63
125.00 ± 34.86 106.70 ± 31.24 0.27
−11.96 ± 22.00
Time Group Interaction
0.325 0.072 4.687
0.576 0.791 0.045
LDL/HDL Pretraining Post-training Effect size
2.23 ± 0.32 2.26 ± 0.57 0.01
2.21 ± 0.93 1.74 ± 0.53 0.38
−16.16 ± 20.64
Time Group Interaction
2.596 1.117 3.472
0.126 0.305 0.08
2.02 ± 23.20
84.90 ± 4.72 84.40 ± 6.65 0.01
(%): relative changes; TBF: fat in the trunk region; BF: total body fat; FFM: fat-free mass; TG: triacylglycerol; TC: cholesterol; HDL-c: high density lipoprotein-cholesterol; LDL-c: low density lipoprotein-cholesterol; LDL/HDL: Atherogenic index. Values were express in mean and standard deviation.
0.98 ± 0.02 and 0.99 ± 0.00, before and after 8 weeks of training, respectively. According to Hill [29], the accuracy of the line of best fit is essential for reliable values, and the present study showed almost perfect linear regression. Unfortunately, the absence of validation of this protocol for postmenopausal women is a limitation of the present study, however, the accuracy of the fit and the effectiveness of aerobic training highlights that this protocol is promising for determining training intensity of postmenopausal women. Several studies aimed to evaluate the effect of aerobic training in the metabolic profile of older adults or postmenopausal women [14,15,30—32]. However, most of them used laboratory and high-cost techniques, which is unfeasible in daily practice because a large share of the population does not have access to these methods. Yassine et al. [15] evaluated the combined effect of 12 weeks of walking and cycling, prescribed at 60 to 85% of maximum heart rate, on the body composition of the elderly. The authors found that the exercise group improved whole body, subcutaneous and visceral fat, and maintained the fat-free mass. Additionally, the same group presented a decrease in TC and LDL-c. Ryan et al. [32] found similar results on body composition after six months of aerobic exercise plus weight loss, performed three times in week for 50 min at 60 to 85% of maximum oxygen uptake. Older adults who performed the intervention presented a decrease in the
percentage of BF, subcutaneous and visceral fat areas, and a maintenance of the fat-free mass. The same research group also investigated the effect of aerobic exercise plus diet control in the metabolic profile of postmenopausal women [14]. The women exercised at approximately 85% of their heart rate reserve for 45 min. After six months, the participants reduced their BF, both in kilograms and by percentage, subcutaneous and visceral fat areas, and unfortunately, the fat-free mass. Moreover, the authors also observed a reduction in the TG and an increase of the HDL-c levels. Supporting this, Kim and Kim [30] found, prescribing the intensity of the exercise using the age-predicted maximal heart rate, after 16 weeks, that the postmenopausal women who engaged in the intervention group, when compared with control group, presented a decrease in whole body and visceral fat, and in TG. Conversely, in a recent study, Di Blasio et al. [13] found that 13 weeks of aerobic training does not improve the metabolic variables, such as BF, in kilograms or percentage, and lipid profile (TC, LDL-c, HDL-c e TG) in postmenopausal women. This result could be mediated because the authors used only the rate of perceived exertion to determine the exercise, and did not use a specific method to determine the intensity threshold (e.g. anaerobic threshold). Although the present study also used the rate of perceived exertion to monitor the training, we prescribed the aerobic training
Aerobic training prescribed using critical velocity and postmenopausal women using CV, avoiding the error of using a subjective method. In addition, Church et al. [33] found that after six months of aerobic training, the percentage of BF, weight, LDL-c and HDL-c did not change in exercise groups compared with control group. These later results can be mediated by the low intensity used to determine the exercise threshold, 50% of the heart hate frequency at the peak VO2 (approximately 50% of maximal heart rate), as well the nonprogression of the intensity in the training season. The majority of the studies with this population used protocols that are rarely determined based on assessments and appropriate physiological indices [34]. The protocol recognized as the ‘‘gold standard’’ for determining aerobic capacity is the MLSS [35], which consists of performing several constant efforts at different intensities. However, determining MLSS in individuals of advanced age is hampered predominantly by the need to determine lactate concentrations and by the duration of the necessary effort (i.e. 30 min). Additionally, although widely used in literature [15] the determination of the intensity using heart rate, may be influenced by factors such as temperature, stress and medication that can compromise the exercise prescription [36,37]. Thus, the determination of the CV can be an interesting alternative for this population, since it considers only the time and the effort to cover distance. Additionally, it is worth emphasizing that in the present study the postmenopausal women showed a reduction in the fat and lipid variables only in eight weeks of training, possibly due to the of the training intensity using CV and the adjustment of the training load after four weeks. The positive outcomes presented by ours and other studies show the effectiveness of aerobic exercise in reducing fat parameters. We believed that the aerobic nature, moderate intensity and average duration of exercise can increase the intracellular AMP/ATP ratio via -adrenergic stimulus. This process is a trigger to the phosphorylation of hormone-sensitive lipase (HSL), which translocates to the lipid droplet and perilipin, a membrane-like protein, by the action of protein kinase A (PKA). Once activated, perilipin releases comparative gene identification (CGI-58) which binds with adipose triacylglycerol lipase (ATGL) and activates it. Activated ATGL generates diacylglycerol, the preferred substrate of HSL that is already located in the lipid droplet. These processes generate, at the end, the release of acids to be used as an energy source in the mitochondria [38]. Furthermore, we also observed the decrease in LDL-c after the aerobic program. It is well established that, in elderly, chronic endurance training can increase the activity of lecithin-cholesterol acyltransferase (LCAT) [39], the enzyme responsible for transferring cholesterol ester to HDL-c, which reduces the activity of the plasmatic cholesterol ester transfer protein (CETP), the enzyme responsible for transferring the ester of HDL-c to other lipoproteins [40]. It is possible that decreased concentrations of LDLc in the plasma, observed in this study, might be attained through the exchange of cholesterol esters from tissues and lipoproteins to the HDL-c. Furthermore, the LDL/HDL ratio presents a positive correlation with CETP [40], thus attenuating this ratio becomes important to the improvement of the anti-atherogenic process.
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Despite these results being of great relevance, it is necessary to mention, as a limitation, the lack of dietary measures and the small number of subjects, which indicate that caution is needed when generalizing the conclusions found here. In summary, the present study suggests that even a short period of aerobic training, prescribed using CV is effective in decreasing the whole BF, central adiposity, total cholesterol and low-density lipoprotein-cholesterol in postmenopausal women. Moreover, the CV emerges as a low-cost, noninvasive and easily applied method that can be used in this population to prescribe walking/running exercises.
Disclosure of interest The authors declare that they have no competing interest.
Acknowledgments This work was supported by Coordination for the Improvement of Higher Level - or Education - Personnel (Capes). We also thank PhD Fabio Santos Lira, PhD Diego Giulliano Destro Christofaro and PhD Camila Buonani for their important contribution.
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ORIGINAL ARTICLE
Short-term program of aerobic training prescribed using critical velocity is effective to improve metabolic profile in postmenopausal women Un programme de court terme d’entraînement aérobique prescrit en utilisant la vitesse critique est efficace pour améliorer le profil métabolique chez les femmes ménopausées T.A. Diniz a,b,∗, A.C.S. Fortaleza a, F.E. Rossi a,b, L.M. Neves a, E.Z. Campos b, I.F. Freitas Junior a a
Center of Studies and Laboratory of Evaluation and Prescription of Motor Activities (CELAPAM), Department of Physical Education, Sao Paulo State University (UNESP), Rua Roberto Simonsen, 305, 19060-900, Presidente Prudente, SP, Brazil b Exercise and Immunometabolism Research Group, Department of Physical Education, Sao Paulo State University (UNESP), 19060-900, Presidente Prudente, SP, Brazil Received 14 February 2015; accepted 23 March 2015 Available online 2 December 2015
KEYWORDS Endurance training; Lipoproteins; Obesity; Menopausal women
∗
Summary Purpose. — The aim of this study was to verify the effectiveness of an eight-week aerobic training prescribed by the critical velocity on metabolic profile. Methods. — The participants were divided into two groups: Aerobic Training (AT [n = 10]) and Control group (CG [n = 9]). Aerobic intensity was prescribed using critical velocity and the women exercised during eight weeks. The trunk body fat (TBF), body fat (BF) and fat-free mass were estimated using DXA. The total cholesterol (TC), low-density lipoprotein (LDL-c), high-density lipoprotein (HDL-c), triacylglycerol and glucose were analyzed in a particular laboratory. Results. — After eight weeks, there were statistically significant differences between AT and CG in TBF (CG = 4.27 ± 5.10 vs. AT = −3.13 ± 4.65; P = 0.006), BF in kg (CG = 2.79 ± 5.91 vs. AT = −2.75 ± 3.01; P = 0.015) and percentage (CG = 1.83 ± 3.67 vs. AT = −2.40 ± 2.67; P = 0.010), LDL-c levels (CG = 10.95 ± 23.63 vs. AT = −11.96 ± 22.00; P = 0.045) and a tendency in TC (GC = 9.00 ± 15.59 vs. AT = −6.67 ± 16.43; P = 0.052).
Corresponding author. E-mail address: [email protected] (T.A. Diniz).
http://dx.doi.org/10.1016/j.scispo.2015.03.006 0765-1597/© 2015 Elsevier Masson SAS. All rights reserved.
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T.A. Diniz et al. Conclusion. — In summary, the present study suggests that even a short-term of aerobic training, prescribed using critical velocity, is effective in decreasing whole body fat, central adiposity and low-density lipoprotein-cholesterol in postmenopausal women. © 2015 Elsevier Masson SAS. All rights reserved.
MOTS CLÉS Entraînement d’endurance ; Lipoprotéines ; Obésité ; Femmes ménopausées
Résumé But. — Le but de cette étude était de vérifier l’efficacité d’un entraînement aérobique de huit semaines prescrit à la vitesse critique du profil métabolique. Méthodes. — Les participants ont été divisés en deux groupes : entraînement aérobique (AT [n = 10]) et groupe de témoin (CG [n = 9]). Des exercices d’aérobique d’intensité ont été prescrits en utilisant la vitesse critique et des exercices pour les femmes pendant huit semaines. La graisse du corps de tronc (TBF), la graisse corporelle (BF) et la masse maigre ont été estimées en utilisant la méthode DXA. Le taux de cholestérol total (TC), la lipoprotéine de basse densité (LDL-c), les lipoprotéines de haute densité (HDL-c), triglycérides et glucose ont été analysés dans un laboratoire particulier. Résultats. — Après huit semaines, il y avait une différence statistiquement significative entre AT et CG dans la TBF (CG = 4,27 ± 5,10 vs −3,13 ± AT = 4,65 ; p = 0,006), BF en kg (GC = 2,79 ± 5,91 vs −2,75 ± AT = 3,01 ; p = 0,015) et le pourcentage (GC = 1,83 ± 3,67 vs AT = −2,40 ± 2,67 ; p = 0,010), niveaux de LDL-c (GC = 10,95 ± 23,63 vs AT = −11,96 ± 22,00 ; p = 0,045) et une tendance en TC (GC = 9,00 ± 15,59 vs −6,67 ± AT = 16,43 ; p = 0,052). Conclusion. — En résumé, la présente étude suggère que même une courte période d’entraînement aérobique, prescrite en utilisant la vitesse critique, est efficace pour réduire la graisse sur tout le corps, l’adiposité centrale, le cholestérol total et le cholestérol de lipoprotéines de basse densité chez les femmes postménopausées. © 2015 Elsevier Masson SAS. Tous droits réservés.
1. Introduction The postmenopausal period is strictly defined by the World Health Organization (WHO) as the permanent cessation of menstruation (12 months of uninterrupted amenorrhea) occurring naturally, by surgery, chemotherapy or radiation, followed by the loss of ovarian activity and leading to decreased secretion of sex hormones, especially estrogen and progesterone [1]. The downregulation in the estrogen’s secretion is related to an increase in the lipogenic genes and the decrease in the lipolytic genes in various tissues, especially in adipose [2,3]. In addition, these women also present low levels of progesterone, which acts as a glucocorticoid receptor antagonist. Glucocorticoids are known for promoting the accumulation of fat in the abdominal region [4]. These postmenopausal events, when associated with unhealthy behaviors such as physical inactivity and inadequate diet, increase the likelihood of these women becoming obese [5,6]. It is well known that obesity is an independent risk factor in the development of several chronic diseases, such as insulin resistance, atherosclerosis and dyslipidemias [7—9], which together contributes to increase the leading cause of death in women, coronary heart disease [10]. Thus, strategies that aim to promote body fat (BF) loss seem promising for these women. The most common physical activity in the elderly is walking/running [11,12]. However, the studies that aimed to assess the effect of walking or running on the metabolic profile in postmenopausal women used mostly invasive, laboratorial and/or high cost
methods to evaluate and determine the intensity of exercise, or only used the rating of perceived exertion without a specific intensity of training, precluding its use in practice [13—15]. In this way, an alternative method used by our laboratory to determine the anaerobic threshold intensity in walking exercise is critical velocity (CV) [16]. CV has its origin in critical power, which was defined as the slope regression line based on the total work done and the corresponding time until exhaustion [17]. Given the critical power model needed to reach the level of exhaustion, Wakayoshi et al. [18] have proposed a new model to determine CV through determination of the time needed to cover a certain distance. Although the last study used swimming as their chosen modality, this protocol was already validated in track running [19]. In addition to the CV being considered a tool to estimate the individual’s aerobic capacity (i.e. maximal lactate steady state), it can also be used for prescribing training. The total energy expenditure is an important consideration in weight loss programs [20]. Therefore, since anaerobic threshold is the boundary between aerobic and anaerobic metabolism, it allows a long-term training (e.g. 35 to 50 min) and shows a high-energy expenditure during and postexercise when compared with low effort intensities [21]. Moreover, the training above the CV (i.e. above anaerobic threshold) would increase the anaerobic metabolism, reducing the fat oxidation during exercise; furthermore, this intensity would turn the exercise an unpleasant activity [22]. However, it still needs to be elucidated whether the CV (evaluated by the distance × time relation) is a useful
Aerobic training prescribed using critical velocity and postmenopausal women method for training prescription for postmenopausal women aiming to improve their metabolic profiles. Thus, the aim of this study was to verify the effectiveness of eight-weeks of aerobic training determined by the CV on body composition (whole and central adiposity), lipid and glycemic profile in postmenopausal women.
2. Materials and methods 2.1. Participants Subjects were invited through television and newspaper advertising to participate in the study. The participants contacted the researchers by phone and an appointment was made in order to carry out a more detailed interview. All measurements were taken at the University Laboratory. The inclusion criteria were: • being in menopause (having had no menstrual cycle for at least one year and a follicle stimulating hormone (FSH) level of 30 U/L or greater) [1]; • not presenting any physical limitations or health problems that could prevent the completion of the assessments and exercise intervention; • presenting a medical certificate to participate in the training; • not having engaged in any systematic physical exercise (i.e.: walking/running, resistance and swimming training, etc.) for at least six months prior to the study; • not receiving treatment for hormone replacement; • signing the consent form. Out of a total of 40 women who participated in the first screening, 31 met all the inclusion criteria and agreed to participate in the study protocol. Moreover, in this study, we excluded the women who were diabetic and hypercholesterolemic (n = 7). Participants were divided into aerobic training (n = 12) and control groups (n = 12) randomly using a method based on block randomization, which consisted of one block (random sequence), of 24 participants, and an allocation ratio of 1:1. The block was composed of 12 women of each group. During the eight weeks of training, five of the 24 women dropped out of the study. The reasons for dropouts included minor injuries; personal/family problems; unspecified reasons; and the accumulation of three consecutive absences or four nonconsecutive absences during one month. The final sample was composed of 19 subjects: aerobic training (n = 10) and control group (n = 9). All procedures used in this study met the criteria of the Ethics in Human Research according to no. 196/96 of the National Health Council - Brasilia - DF. All participants included in the study signed an informed consent approved by the Ethics in Research Committee from the university linked to the project (Protocol: 64/2011).
2.2. Methods This intervention study was carried out from February to July of 2013 at Sao Paulo State University (UNESP), Presidente Prudente, Brazil. The initial assessment occurred two weeks before the baseline moment (M0) and, consisted of
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the anamnesis to verify whether the participants met the inclusion criteria. At this time, anthropometry and body composition were evaluated. After eight-weeks of intervention, all measurements were repeated (M8). The training group performed eight weeks of aerobic training and the control group maintained a sedentary lifestyle for 8 weeks, without participating in any regular physical exercise. Both groups were asked to maintain the pattern of nutrition intakes. All measurements were made by trained evaluators who are studying physical education at UNESP, and the training seasons were always supervised by graduate students and physical education students.
2.3. Anthropometric measurements and body composition Before the anthropometric evaluation, the female study participants were requested to attend the evaluation day barefoot and wearing light clothing. Anthropometry was composed of body weight and height measurements. Height was measured on a Sanny brand fixed stadiometer, with an accuracy of 0.1 cm and length of 2.20 m. Body weight was measured using an electronic scale (Filizola PL 50, Filizzola Ltda., Brasil), with a precision of 0.1 kg. The body composition was estimated using a DXA scanner, version 4.7 (General Electric Healthcare, Lunar DPX-NT; England). The subjects were positioned in a supine position and remained immobile throughout the examination. Total BF in percentage and kilograms, fat located in the trunk region (TBF), and fat-free mass (FFM) were assessed and expressed in absolute and relative values by the DEXA software. The TBF was estimated in the abdominal region, and was defined as 20% of the length from a circumference line at the pelvis to a circumference line at the neck. All measurements were carried out at the University Laboratory in a temperature-controlled room. Each morning, before the beginning of the measurements, the equipment was calibrated by the same researcher, according to the manufacturer’s instructions.
2.4. Blood samples After an overnight fast (12 h), venous blood samples were collected to measure glucose, triglycerides (TG), fasting total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c) and low-density lipoprotein cholesterol (LDL-c), using the colorimetric technique in dry chemical and Johnson and Johnson equipment, model Vitros 250. The Friedewald et al. [23] formula was used to calculate the LDL-c concentration.
2.5. Aerobic training protocol The determination of the intensity of the aerobic training was performed using the CV protocol proposed by Wakayoshi et al. [18]. The aerobic training group travelled three distances (400, 800 and 1200 m) on a running track on separate, nonconsecutive, days. The participants were instructed to cover the distance in the shortest possible time, which was recorded using a digital stopwatch (Polar® ).
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Figure 1 Example of a subject relation between distance performed and time to complete, and linear regression. Critical velocity was assumed as the angular coefficient of the relation (i.e. 1.44 m·s−1 ).
A linear regression was obtained by the relation between distance (meters) and time (seconds). The CV was assumed by the angular coefficient of linear regression straight line between the distances and the respective times obtained in each repetition [18] (Fig. 1). Before the beginning of the training, the participants performed two weeks of familiarization, which consisted of walking, gradually, until reach the volume of the training (50 min). The training volume was equivalent to 50 min/day at 100% of CV. Each exercise session included a 5- to 10-min warm-up and a 5- to 10-min cool down. After four weeks, the procedures of CV were repeated to determine and adjust the intensities to next four weeks of training. Participants were instructed to drink water and wear appropriate shoes and clothing during training. The rating of perceived exertion was determined at the end of each session [24].
2.6. Statistical analysis The data normality was verified using the Shapiro-Wilk test. The descriptive analyses consisted of the mean and standard deviations. Initially, in order to identify the homogeneity of both groups at baseline (basic assumption), dependent variables were compared between the control group and aerobic training group using the Student t test for independent samples. In the longitudinal analysis, the comparison of the metabolic profile between the two groups was conducted by repeated measurements analyses and the differences were calculated by the ‘‘mean percentage differences’’ ([Final Moment—Baseline moment]/Baseline moment * 100), also performing a two-way repeated measure of ANOVA (group × time). When a significant difference in group or interaction was observed, the Tukey post hoc test was conducted. For all measured variables, the estimated sphericity was verified according to Mauchly’s W test, and the Greenhouse—Geisser correction was used when necessary. The effect size was calculated using Eta-square test.
T.A. Diniz et al.
Figure 2 Mean and individual changes in the critical velocity (angular coefficient) pre and post eight-weeks of aerobic training.
All analyses were performed using the statistical software SPSS (version 13.0). The level of significance was set at 5%.
3. Results The sample’s mean age was 61.5 ± 7.4 years and the average percentage of BF was 42.8 ± 5.2. No significance difference was found between the variables of body composition, anthropometric, and age at the first moment (Table 1), thus, indicating that the groups were homogenous. The linear regression of the relation distance vs. time for the CV determinant presented a determinant coefficient of 0.98 ± 0.02 and 0.99 ± 0.00, before and after 8 weeks of training, respectively. Fig. 2 shows group and individual changes in the CV after eight weeks of aerobic training. The CV increased significantly after 8 weeks of aerobic training (5.32 ± 0.70 km·h−1 and 6.43 ± 0.90 km·h−1 ; P < 0.001). Tables 2 and 3 present the relative changes in metabolic profile after eight weeks of aerobic training. The women who were engaged in the intervention decreased their total BF, both absolute and by percentage. When comparing the control and aerobic group, the latter showed a statistically significant decrease in the fat located in the trunk region (kg), total BF (kg), LDL-c and a tendency in total cholesterol. Moreover, the LDL/HDL ratio decreased more than 16 percent in the exercise group, although it was not statistically significant (P = 0.080).
4. Discussion The aim of the present study was to evaluate the effectiveness of aerobic training as determined by the CV in the body composition and metabolic parameters of postmenopausal women. The main findings of the present study were that training eight weeks in the CV was effective in reducing the total and trunk BF, LDL, and TC concentration. Moreover, CV is promising to determine and prescribe the aerobic training intensity for postmenopausal women. Aerobic training has been presented as a nonpharmacological treatment to prevent metabolic and cardiac
Aerobic training prescribed using critical velocity and postmenopausal women
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Table 1 Comparison between the control and aerobic group in the variables of anthropometric, body composition and metabolic profile at the first moment. Variables
Control (n = 9)
Age (years) Weight (kg) BMI (kg/m2 ) TBF (kg) BF (kg) BF (%) FFM (kg) Glucose (mg/dL) Triacylglycerol (mg/dL) Cholesterol (mg/dL) HDL-c (mg/dL) LDL-c (mg/dL) LDL/HDL ratio
62.01 61.51 25.76 13.49 26.09 42.02 33.33 91.22 125.11 190.44 51.11 113.89 2.23
± ± ± ± ± ± ± ± ± ± ± ± ±
Aerobic (n = 10)
7.83 7.68 2.93 2.63 5.74 4.94 3.20 9.19 51.50 34.73 8.57 25.77 0.32
60.26 62.67 25.82 14.27 26.91 42.47 33.48 84.90 92.80 203.60 60.00 125.00 2.21
± ± ± ± ± ± ± ± ± ± ± ± ±
P-value
8.51 7.87 2.74 2.96 6.48 5.89 3.05 4.72 32.22 35.18 12.70 34.86 0.93
0.649 0.749 0.961 0.555 0.774 0.859 0.916 0.072 0.116 0.424 0.095 0.445 0.942
BF: fat in the trunk region; BF: total body fat; FFM: fat-free mass; HDL-c: high-density lipoprotein-cholesterol; LDL-c: low-density lipoprotein-cholesterol; LDL/HDL: Atherogenic index. Values were express in mean and standard deviation.
dysfunction on a wide range of subjects, especially in obese, elderly, and type 2 diabetes patients [25]. However, to ensure beneficial results from aerobic training, the training intensity should be prescribed individually (i.e. anaerobic threshold) [26], and not on a wide range of intensities (i.e. 60—85% of maximal HR), that might elicit different relatives anaerobic threshold intensities [27]. Even though a large number of tests are available to describe aerobic training,
Table 2
they are usually maximal (to exhaustion) and invasive, being difficult to apply in older subjects. Recently, Rossi et al. [28] have tested the reliability and validation of a nonexhaustive CV test to estimate the maximal lactate steady state (MLSS) in postmenopausal women, and found that the test cannot be used to estimate the aerobic capacity. In the present study, the distance vs. time relation during the CV test presented a determinant coefficient of
Characteristics of subjects before and after the exercise program on the body composition.
Variables
Control (n = 9) Mean ± SD
Aerobic (n = 10) Mean ± SD % 0.91 ± 2.73
% −0.76 ± 2.23
Anova
F
P
Time Group Interaction
0.038 0.028 2.541
0.848 0.869 0.129
Weight (Kg) Pretraining Post-training Effect size
61.51 ± 7.68 62.13 ± 8.39 0.13
TBF (kg) Pretraining Post-training Effect size
13.49 ± 2.63 14.13 ± 3.13 0.44
4.27 ± 5.10
14.27 ± 2.96 13.87 ± 3.20 0.27
−2.75 ± 3.01
Time Group Interaction
0.551 0.037 9.818
0.468 0.85 0.006
BF (Kg) Pretraining Post-training Effect size
26.09 ± 5.74 26.95 ± 6.71 0.25
2.79 ± 5.91
26.91 ± 6.48 26.23 ± 6.66 0.45
−2.75 ± 3.01
Time Group Interaction
0.109 0 7.335
0.745 0.985 0.015
BF (%) Pretraining Post-training Effect size
42.02 ± 4.94 42.84 ± 5.72 0.24
1.83 ± 3.67
42.47 ± 5.89 41.47 ± 6.04 0.43
−2.40 ± 2.67
Time Group Interaction
0.082 0.031 8.392
0.778 0.861 0.01
FFM (Kg) Pretraining Post-training Effect size
33.33 ± 3.20 33.06 ± 3.07 0.1
−0.75 ± 2.36
33.48 ± 3.05 33.64 ± 2.61 0.03
0.61 ± 2.99
Time Group Interaction
0.069 0.072 1.001
0.795 0.791 0.331
62.67 ± 7.87 62.18 ± 7.79 0.13
%: relative changes; TBF: fat in the trunk region; BF: total body fat; FFM: fat-free mass; TG: triacylglycerol; TC: cholesterol; HDL-c: high density lipoprotein-cholesterol; LDL-c: low density lipoprotein-cholesterol; LDL/HDL: Atherogenic index. Values were express in mean and standard deviation.
100 Table 3
T.A. Diniz et al. Characteristics of subjects before and after the exercise program on the lipid profile.
Variables
Control (n = 9) Mean ± SD
Aerobic (n = 10) Mean ± SD % −1.38 ± 12.51
Anova
F
P
Time Group Interaction
0.451 5.253 0.172
0.511 0.035 0.684
3.41 ± 24.65
Time Group Interaction
0 4.475 0.003
0.998 0.049 0.955
−6.67 ± 16.43
Time Group Interaction
0.001 0.015 4.366
0.977 0.905 0.052
5.06 ± 11.00
Time Group Interaction
5.106 2.794 0.216
0.037 0.113 0.648
% −0.54 ± 6.54
Glucose (mg/dl) Pretraining Post-training Effect size
91.22 ± 9.19 89.11 ± 5.78 0.04
TG (mg/dl) Pretraining Post-training Effect size
125.11 ± 51.50 124.67 ± 30.62 0.01
13.97 ± 60.86
92.80 ± 32.22 93.20 ± 28.79 0.01
TC (mg/dl) Pretraining Post-training Effect size
190.44 ± 34.73 205.22 ± 34.27 0.25
9.00 ± 15.59
203.60 ± 35.18 188.40 ± 41.15 0.18
HDL-c (mg/dl) Pretraining Post-training Effect size
51.11 ± 8.57 55.67 ± 7.50 0.24
11.05 ± 20.37
60.00 ± 12.70 63.00 ± 13.96 0.22
LDL-c (mg/dl) Pretraining Post-training Effect size
113.89 ± 25.77 124.56 ± 30.75 0.16
10.95 ± 23.63
125.00 ± 34.86 106.70 ± 31.24 0.27
−11.96 ± 22.00
Time Group Interaction
0.325 0.072 4.687
0.576 0.791 0.045
LDL/HDL Pretraining Post-training Effect size
2.23 ± 0.32 2.26 ± 0.57 0.01
2.21 ± 0.93 1.74 ± 0.53 0.38
−16.16 ± 20.64
Time Group Interaction
2.596 1.117 3.472
0.126 0.305 0.08
2.02 ± 23.20
84.90 ± 4.72 84.40 ± 6.65 0.01
(%): relative changes; TBF: fat in the trunk region; BF: total body fat; FFM: fat-free mass; TG: triacylglycerol; TC: cholesterol; HDL-c: high density lipoprotein-cholesterol; LDL-c: low density lipoprotein-cholesterol; LDL/HDL: Atherogenic index. Values were express in mean and standard deviation.
0.98 ± 0.02 and 0.99 ± 0.00, before and after 8 weeks of training, respectively. According to Hill [29], the accuracy of the line of best fit is essential for reliable values, and the present study showed almost perfect linear regression. Unfortunately, the absence of validation of this protocol for postmenopausal women is a limitation of the present study, however, the accuracy of the fit and the effectiveness of aerobic training highlights that this protocol is promising for determining training intensity of postmenopausal women. Several studies aimed to evaluate the effect of aerobic training in the metabolic profile of older adults or postmenopausal women [14,15,30—32]. However, most of them used laboratory and high-cost techniques, which is unfeasible in daily practice because a large share of the population does not have access to these methods. Yassine et al. [15] evaluated the combined effect of 12 weeks of walking and cycling, prescribed at 60 to 85% of maximum heart rate, on the body composition of the elderly. The authors found that the exercise group improved whole body, subcutaneous and visceral fat, and maintained the fat-free mass. Additionally, the same group presented a decrease in TC and LDL-c. Ryan et al. [32] found similar results on body composition after six months of aerobic exercise plus weight loss, performed three times in week for 50 min at 60 to 85% of maximum oxygen uptake. Older adults who performed the intervention presented a decrease in the
percentage of BF, subcutaneous and visceral fat areas, and a maintenance of the fat-free mass. The same research group also investigated the effect of aerobic exercise plus diet control in the metabolic profile of postmenopausal women [14]. The women exercised at approximately 85% of their heart rate reserve for 45 min. After six months, the participants reduced their BF, both in kilograms and by percentage, subcutaneous and visceral fat areas, and unfortunately, the fat-free mass. Moreover, the authors also observed a reduction in the TG and an increase of the HDL-c levels. Supporting this, Kim and Kim [30] found, prescribing the intensity of the exercise using the age-predicted maximal heart rate, after 16 weeks, that the postmenopausal women who engaged in the intervention group, when compared with control group, presented a decrease in whole body and visceral fat, and in TG. Conversely, in a recent study, Di Blasio et al. [13] found that 13 weeks of aerobic training does not improve the metabolic variables, such as BF, in kilograms or percentage, and lipid profile (TC, LDL-c, HDL-c e TG) in postmenopausal women. This result could be mediated because the authors used only the rate of perceived exertion to determine the exercise, and did not use a specific method to determine the intensity threshold (e.g. anaerobic threshold). Although the present study also used the rate of perceived exertion to monitor the training, we prescribed the aerobic training
Aerobic training prescribed using critical velocity and postmenopausal women using CV, avoiding the error of using a subjective method. In addition, Church et al. [33] found that after six months of aerobic training, the percentage of BF, weight, LDL-c and HDL-c did not change in exercise groups compared with control group. These later results can be mediated by the low intensity used to determine the exercise threshold, 50% of the heart hate frequency at the peak VO2 (approximately 50% of maximal heart rate), as well the nonprogression of the intensity in the training season. The majority of the studies with this population used protocols that are rarely determined based on assessments and appropriate physiological indices [34]. The protocol recognized as the ‘‘gold standard’’ for determining aerobic capacity is the MLSS [35], which consists of performing several constant efforts at different intensities. However, determining MLSS in individuals of advanced age is hampered predominantly by the need to determine lactate concentrations and by the duration of the necessary effort (i.e. 30 min). Additionally, although widely used in literature [15] the determination of the intensity using heart rate, may be influenced by factors such as temperature, stress and medication that can compromise the exercise prescription [36,37]. Thus, the determination of the CV can be an interesting alternative for this population, since it considers only the time and the effort to cover distance. Additionally, it is worth emphasizing that in the present study the postmenopausal women showed a reduction in the fat and lipid variables only in eight weeks of training, possibly due to the of the training intensity using CV and the adjustment of the training load after four weeks. The positive outcomes presented by ours and other studies show the effectiveness of aerobic exercise in reducing fat parameters. We believed that the aerobic nature, moderate intensity and average duration of exercise can increase the intracellular AMP/ATP ratio via -adrenergic stimulus. This process is a trigger to the phosphorylation of hormone-sensitive lipase (HSL), which translocates to the lipid droplet and perilipin, a membrane-like protein, by the action of protein kinase A (PKA). Once activated, perilipin releases comparative gene identification (CGI-58) which binds with adipose triacylglycerol lipase (ATGL) and activates it. Activated ATGL generates diacylglycerol, the preferred substrate of HSL that is already located in the lipid droplet. These processes generate, at the end, the release of acids to be used as an energy source in the mitochondria [38]. Furthermore, we also observed the decrease in LDL-c after the aerobic program. It is well established that, in elderly, chronic endurance training can increase the activity of lecithin-cholesterol acyltransferase (LCAT) [39], the enzyme responsible for transferring cholesterol ester to HDL-c, which reduces the activity of the plasmatic cholesterol ester transfer protein (CETP), the enzyme responsible for transferring the ester of HDL-c to other lipoproteins [40]. It is possible that decreased concentrations of LDLc in the plasma, observed in this study, might be attained through the exchange of cholesterol esters from tissues and lipoproteins to the HDL-c. Furthermore, the LDL/HDL ratio presents a positive correlation with CETP [40], thus attenuating this ratio becomes important to the improvement of the anti-atherogenic process.
101
Despite these results being of great relevance, it is necessary to mention, as a limitation, the lack of dietary measures and the small number of subjects, which indicate that caution is needed when generalizing the conclusions found here. In summary, the present study suggests that even a short period of aerobic training, prescribed using CV is effective in decreasing the whole BF, central adiposity, total cholesterol and low-density lipoprotein-cholesterol in postmenopausal women. Moreover, the CV emerges as a low-cost, noninvasive and easily applied method that can be used in this population to prescribe walking/running exercises.
Disclosure of interest The authors declare that they have no competing interest.
Acknowledgments This work was supported by Coordination for the Improvement of Higher Level - or Education - Personnel (Capes). We also thank PhD Fabio Santos Lira, PhD Diego Giulliano Destro Christofaro and PhD Camila Buonani for their important contribution.
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