resistance training and changes to plasma lipoproteins in postmenopausal women

Objectives. The main purpose of this study was to assess the effect of progressive resistance training on the blood lipid profile in postmenopausal women. Methods. Twenty-six female participants aged 50 - 75 years were selected from the population of Grahamstown, South Africa. All participants were previously sedentary and possessed at least one lipid profile abnormality but were otherwise healthy. Pretests included a sub-maximal stress test, stature, mass, central and limb girths as well as an oral glucose tolerance test (OGTT) and a total blood lipid profile. Participants took part in a 24-week progressive resistance training programme, consisting of three supervised sessions per week, each lasting 45 minutes. Participants were not permitted to lose more than 10% of initial body mass during the 24-week study. All pre-test measures, excluding the stress test and the OGTT, were repeated every 4 weeks for the duration of the study. Results. Body mass, body mass index and waist-to-hip ratio did not change. Girth measures at mid-humerus, chest, waist, hip, mid-quadricep and mid-gastrocnemius all decreased significantly ( p <0.05). LDL-cholesterol increased significantly over the course of 24 weeks (3.61 mmol.l -1 to 4.07 mmol.l -1 ), as did total cholesterol (5.81 mmol.l -1 - 6.24 mmol.l-1). Triglyceride concentration remained unchanged and HDL-cholesterol decreased significantly between the pre-test measure (1.55 mmol.l -1 ) and the measure after 6 months (1.42 mmol.l -1 ). Conclusion. The blood lipid profile in a sample of postmenopausal women was not positively affected by a progressive resistance training programme over a 24-week period.


abstract objectives.
The main purpose of this study was to assess the effect of progressive resistance training on the blood lipid profile in postmenopausal women.Methods.Twenty-six female participants aged 50 -75 years were selected from the population of Grahamstown, South Africa.All participants were previously sedentary and possessed at least one lipid profile abnormality but were otherwise healthy.Pretests included a sub-maximal stress test, stature, mass, central and limb girths as well as an oral glucose tolerance test (OGTT) and a total blood lipid profile.Participants took part in a 24-week progressive resistance training programme, consisting of three supervised sessions per week, each lasting 45 minutes.Participants were not permitted to lose more than 10% of initial body mass during the 24-week study.All pre-test measures, excluding the stress test and the OGTT, were repeated every 4 weeks for the duration of the study.results.Body mass, body mass index and waist-to-hip ratio did not change.Girth measures at mid-humerus, chest, waist, hip, mid-quadricep and mid-gastrocnemius all decreased significantly (p<0.05).LDL-cholesterol increased significantly over the course of 24 weeks (3.61 mmol.l - to 4.07 mmol.l - ), as did total cholesterol (5.81 mmol.l - -6.24 mmol.l - ).Triglyceride concentration remained unchanged and HDL-cholesterol decreased significantly between the pre-test measure (1.55 mmol.l-1 ) and the measure after 6 months (1.42 mmol.l - ).
conclusion.The blood lipid profile in a sample of postmenopausal women was not positively affected by a progressive resistance training programme over a 24-week period.
as less than three regular sessions of physical activity of 30 minutes' duration per week for the previous 6 months, based on the American College of Sports Medicine's recommendation that three sessions of exercise weekly, each of 30 minutes, is minimally beneficial to the individual), free from heart, lung, liver and kidney disease, not on hormone replacement therapy and non-diabetic or pre-diabetic.The latter was assessed through an oral glucose tolerance test (OGTT) conducted prior to the study, results of which were used specifically to screen for irregularities and were not included as part of the study thereafter.

Measurements
Clinical evaluation included a stress echocardiogram (ECG), resting blood pressure while standing, sitting and supine, and a full physical examination by a medical practitioner.A full OGTT was carried out at a reputable pathology laboratory.Participants were required to fast from 22h00 the evening before the OGTT, and presented at the laboratory at 08h30.On arrival at the laboratory each participant was given a glucose solution to consume, mixed to specification (75 g of glucose mixed in water).A blood sample was taken within 2 minutes of consumption of the glucose drink and again 2 hours later.In between the two blood tests participants were permitted to leave the laboratory but were not permitted to eat or drink anything other than small amounts of water if required.
Anthropometric parameters included measures of stature, mass, and girth measures at the following anatomical sites: mid-humerus, chest over-bust, waist at the level of the umbilicus, hip, midquadricep and mid-gastrocnemius (Table I).Girth measures (upper arm, chest over-bust, waist, hip, thigh and calf) and mass (kg) were obtained by the principal researcher and were measured at the start of the same 60-minute exercise session on each occasion at 4-week intervals.Two measurements were taken and if these matched the researcher was satisfied that the measurement was valid.The following anthropometric indicators were calculated: waist-to-hip ratio and body mass index (Table I).
Full, fasting blood lipid profiles were obtained at a reputable pathology laboratory.
Blood was analysed using standard automated enzymatic processes on the Dimension Xpand Plus clinical chemistry system.The following serum determinations were made from samples collected in the morning after a 12-hour fast: total cholesterol, high-density cholesterol (HDL-C) and triglycerides (enzymatic method) and low-density lipoprotein cholesterol (LDL-C) (estimation 16 ).For inclusion in the study, participants had to present with at least one lipid abnormality (total cholesterol higher than 5.20 mmol.l - ; LDL above 2.60 mmol.l - ; HDL above 1.30mmol.l - or triglycerides above 1.70 mmol.l - ) and not present with an abnormal fasting blood glucose response.Measurements were repeated every 4 weeks.

Training protocol
A 24-week progressive resistance training (PRT) programme was designed engaging the 'FIND' principle (frequency, intensity, nature and duration).In order to ensure reliability and validity of results intensity was tightly monitored throughout the study.Initial intensity was set at 50% one-repetition-maximum (1-RM) and increased to 80% during the final phases of the project.The major muscle groups targeted are shown in Table II.Participants were also required to attend three sessions per week for the 24-week study trial.Although requested to maintain their habitual dietary intake for the duration of the study (and participants were regularly explained the reason as to why this was important), a limitation of the study is that diet was not monitored or controlled.This represents a weakness in the design of this study, of which the authors are aware.In executing this protocol the researcher intended to conduct a field study, replicating ordinary daily life so that the results might indicate the efficacy of lifestyle interventions in situ.In addition, this was a preliminary study for a further investigation, the design for which includes many improvements including better control of the participants' dietary intake.
The exercise programme was divided into six phases of 4 weeks' duration (Table III).Each phase represented an increase in intensity, initially by increasing the intensity from 50% of the 1-RM to 60% of the 1-RM, and then by increasing both the intensity and also the volume of repetitions and sets completed.Exercise sessions were offered at times self-selected by the participants.Each session was supervised by a research assistant (postgraduate students in the Department of Human Kinetics and Ergonomics, Rhodes University, Grahamstown).Participants were required to attend three sessions weekly, each lasting 45 -60 minutes.The aerobic warm-up comprised 10% of the session time, and the PRT portion of the workout made up 90% of the session time.Inclusion in data analyses was dependent on the participant completing 80% of the sessions (72 sessions in total).

statistical analyses
Data are presented as mean ± standard deviation (SD).Statistical significance was set at p≤0.05.A repeated measures one-way analysis of variance (ANOVA) was employed to analyse the results, and statistical procedures were performed in Statistica 8.

results compliance
In order to be included in the data set participants had to attend at least 80% of the total number of sessions (72).Of the initial sample (N=34) 87% completed 80% of the sessions and of this number, 9% attended 100% of the sessions.Of the remaining participants 3% attended 70 -75% of sessions, and 10% had only attended 50 -60% of the 72 sessions.Data from 26 participants were analysed once results had been corrected for compliance.

anthropometric and girth measures
Body mass (kg) did not display significant changes (-0.77±0.62 kg) over the course of 24 weeks (p<0.05).

Discussion
This study evaluated the effect of progressive resistance training on the plasma lipoproteins in postmenopausal women.Reliability of results required that the compliance of participants remained high.Thus, only those participants who achieved at least 80% attendance at exercise sessions were included in the data analyses.Furthermore, it was important for the outcomes of the study that the sample did not lose more than 10% of baseline body mass, as it has been demonstrated that weight loss positively influences plasma lipoprotein concentrations. 19,20   after 24 weeks).Other girth measures were positively affected by the exercise programme.In particular, reductions at central and distal anatomical sites with a concomitantly stable body mass reflected a decrease in fat mass and a possible increase in fat-free mass (given that body mass remained stable).This is in contrast to the findings of Joseph et al., 12 who found that 12 weeks of resistance training reflected no change in body composition in postmenopausal women, while in their age-matched male participants, body fat was reduced.At 12 weeks in the current sample, all girth measures were positively responding (p<0.05) to the exercise programme.
Plasma LDL increased from as early as 4 weeks into the study (an increase of 0.17±0.36mmol.l - compared with the pre-test baseline measure).This sharp increase leveled off at week 8 (0.02±0.17 mmol.l - ) but by week 12 LDL had increased by 6% relative to the baseline measure, and at week 24 LDL was significantly higher (12%) than pre-test.The changes in LDL cholesterol were not supported by recent literature, 12,21,22 which reported that resistance training in postmenopausal women resulted in no change to LDL levels.Important to note however is that the current study was 24 weeks in duration with this time frame resulting in a significant increase in LDL.At 12 weeks LDL had also not significantly altered effectively, suggesting that had the studies of Joseph et al,. 12Fahlmann et al.HDL decreased significantly from baseline to 16 weeks (-3%) and 24 weeks (-8%), which is a finding supported by Joseph et al. 12 In contrast to this it was found that resistance training had no effect on HDL concentrations in samples of middle-aged men. 23 Triglyceride (TG) concentration reached a significant 20% (p<0.05)above the baseline value at week 8 (0.31±0.32 mmol.l-1 higher than the pre-test plasma triglyceride levels).Over the following 16 weeks the plasma concentration of triglycerides appeared to decrease steadily, returning to pre-test levels at 24 weeks.Similarly, in another study, no changes were found in triglyceride levels after 12 weeks of resistance training.12   The drop and then subsequent increase in TG concentrations must be viewed within the context of the study design.TG levels are known to be influenced by many lifestyle-related factors such as dietary intake, alcohol consumption, smoking and menstrual status, to name a few. 4 While smoking and menstrual status were controlled for in this study, no controls were instituted for alcohol intake, dietary or any other lifestyle habits.The drop in TG after 8 weeks therefore could have been a consequence of subconscious (or possibly even conscious) altered habitual lifestyle as it is well known that when individuals start exercising, diet is often changed subconsciously and individuals tend to start living a healthier lifestyle. 6Motivation for healthier lifestyle habits may have reduced over time and hence the increase in TG levels back to baseline may, again, be due to poorer lifestyle choices outside of the exercise influence.Interestingly however is the fact that although body fat was not measured, it was postulated that there was a decrease in fat mass and an increase in LBM as reflected by the changes in girth measures.Evidence suggests that this should positively alter TG concentration 13 and yet this was not the case.Either body composition was not altered due to the exercise intervention or the other lifestyle choices made by the participants could have negated the positive body composition effect.The latter is the more plausible.
Total cholesterol (TC) increased significantly (p<0.05) by week 16 (an increase of 7%) and was significantly elevated from baseline at both 20 and 24 weeks, which is in contrast to previous findings.14 Despite this significant change, it is important to note the clinical significance of these findings as at 24 weeks, the increase from baseline was only 0.43±0.15mmol.l - .Current recommended levels of the plasma lipoproteins are HDL ˃0.90 mmol.l - , LDL ≤3.00 mmol.l-1 (but ≤1.50 mmol.l - for those with known cardiac risk), triglycerides <1.70 mmol.l - and TC ≤5.00 mmol.l - . 27The current sample fell within the 'borderline' category prior to the exercise intervention for LDL (3.61 mmol.l - ) and TC (5.81 mmol.l - ), and within the desirable range for both HDL (1.55 mmol.l-1) and triglyceride concentration (1.54 mmol.l - ).Following the training intervention these values had shown statistically significant changes (p<0.05),but did not show clinically significant permutations.LDL remained within the 'borderline' category (4.07 mmol.l - at 24 weeks), HDL remained at desirable levels (1.42 mmol.l - ) and TC was still below 7.50 mmol.l - , which is the upper limit of the 'borderline risk' category (6.24 mmol.l-1 at 24 weeks).TG concentrations above 2.26 mmol.l - would reflect hypertriglyceridaemia, 27 but the TG concentrations for the current sample remained below this margin (1.54 mmol.l-1prior to the intervention and 1.65 mmol.l - at 24 weeks).

conclusion
Although these findings suggest a negative lipoprotein response to resistance training in postmenopausal women, the findings should be interpreted within the context of the study design and in the light of clinical significance.This especially in light of the fact that dietary intake was not strictly controlled or monitored and that there was no comparative control group.Future studies should consider these factors.The large variation in results obtained indicates that a mechanism for positive change exists and requires a more strictly controlled study to become clearly evident.

21 and
Behall et al.22 been continued for longer, they too may have seen an increase in LDL levels.Furthermore, in the study by Joseph et al. body composition was not altered, unlike in this study where body composition positively changed.