Effects of different exercise training intensities on lipoprotein cholesterol fractions in healthy middle-aged men Exercise training has been associated with decreases in total cholesterol and increases in high-density lipoprotein (HDL) cholesterol. The effect of the intensity of the exercise on alterations in cholesterol and lipoprotein fractions has not been defined and is the subject of this study. We divided 49 healthy men (aged 44 +_ 8 years) into four groups and evaluated them before and after 12 weeks of cycle ergometer exercise training at (1) an intensity of 65% of maximal achieved heart rate, (2) 75% maximal heart rate, (3) 85% maximal heart rate, and (4) a 12-week nonexercise control period. Pre- and post-training evaluations included maximal ergometer exercise ECG examinations with measurement of maximal minute oxygen consumption and serum total cholesterol, HDL cholesterol, and triglyceride levels. Low-density (LDL) and very low-density lipoprotein (VLDL) cholesterol levels were calculated. Dietary histories were obtained before and after the training period, and body weight and percentage of body fat were measured. Post-training oxygen uptake was significantly increased (training effect) in the groups exercising to 65%, 75%, and 85% maximal heart rate. Results of within-group analysis showed significant increases in the HDL cholesterol fractions in the 75% and 85% groups but not in the 65% group or the control group. Significant decreases in calculated LDL fractions occurred only in the 75% exercise-trained group with maximal heart rate. Aerobic exercise training favorably alters plasma lipoprotein profiles. A minimum training intensity equal to 75% maximal heart rate is required to the increase HDL cholesterol level. (AM HEART J 1990;119:277.)
R i c h a r d A. Stein, MD, D o n a l d W. Michielli, P h D , M o r t o n D. Glantz, PhD, H y m a n Sardy, PhD, Arlette Cohen, PhD, Nieca Goldberg, MD, and Clinton D. Brown, MD. Brooklyn, N.Y.
T h e r e is an increasing b o d y of d a t a to s u p p o r t the direct relationship of low-density lipoprotein (LDL) cholesterol a n d the inverse relationship of high-density lipoprotein ( H D L ) cholesterol to risk of developing coronary a r t e r y disease. TM Modification of factors t h a t favorably reduce total serum cholesterol levels and favorably alter the ratio of H D L and L D L cholesterol is thus of great interest and the subject of continuing investigations3 -8 T h e role of exercise in altering lipoproteins has been studied with differing conclusions, 9-11 in p a r t explainable by differences in protocols a n d the absence of control groups. M a n y studies r e p o r t e d to date, however, have been poorly controlled with regard to the amount, duration, and intensity of the exercise performed. 12,14-17This s t u d y From the State Universityof New York-HealthScienceCenterat Brooklyn, and BrooklynCollege. Receivedfor publicationMarch 7, 1989;acceptedSept. 15, 1989. Reprint requests:RichardA. Stein,MD, SUNY-HealthScienceCenterat Brooklyn,450 ClarksonAve.,Brooklyn,NY 11203. 4/1/17361
determines the effect(s) of exercise training intensity on plasma lipids and lipoproteins and determines whether there is a threshold training intensity below which such salutary changes would not occur during a relatively short training period. METHODS Subjects. Forty-nine male faculty and staff members at
Brooklyn College were selected from among a larger pool of volunteers for inclusion in the study. The mean age was 44 _+ 8 years. Criteria for selection included a normal resting 12-lead ECG, no history or symptoms of cardiac disease, and no abnormalities in heart rate, ST segment, or blood pressure response during a symptom-limited maximal exercise ECG examination. Maximal exercise ECG studies. All subjects underwent maximal exercise ECG studies with continuous multilead ECG monitoring; a continuous cycle ergometer protocol was used (starting at a work load of 300 kpm and increasing by 100 kpm every 2 minutes). This was performed to exhaustion before and immediately after the exercise training or control period. Expired air was collected by means of open-circuit methodology,19 minute uptake con277
278
February 1990 American Heart Journal
Stein et al.
Table I. Comparison of body weight, percentage of body fat, and VO2max among control and three test groups before and after 12-week exercise training period Control ( N = 10)
Body weight (kg) Before 82.2 + 7.8 (NS) After 82.25 _+5.4 Body fat (%) Before 27.4 + 1.6 (NS) After 26.6 +_ 1.6 VO2m~ (ml/kg/min) Before 30.4 +_ 1.8 (NS) After 31.7 _+ 1.7
65 % ( N = 13)
75 % ( N = 14)
85 % ( N = 12)
70.5 _+ 2.8 (NS) 70.5 +_2.9
82.8 _+5.2 (NS) 82.6 _+5.1
84.4 _+8.2 (NS) 84.0 _+7.2
23.8 _+ 1.5 (NS) 23.7 _+ 1.5
26.8 _+0.5 (NS) 26.5 _+ 1.1
27.5 _+ 2.0
28.4 _+ 1.3 (p < 0.05) 31.5 _+ 1.5
30.3 _+ 1.3 (p < 0.05) 35.9 + 1.0
25.1 ___2.0 (p < 0.01) 35.9 + 3.8
28.4 +_ 2.1
(NS)
NS, Not significant.
sumption (V02) was measured, and maximal minute oxygen uptake (VO2max) was determined for each subject. Blood studies. Fasting morning blood samples were obtained from all subjects before and immediately after the exercise training or control period. Blood samples were drawn from the medial vein into tubes containing EDTA. Plasma was separated by centrifugation, and samples were stored at - 1 0 ~ C until assays were determined (within 48 hours) in all samples. All assays were done in duplicate or triplicate--in triplicate if variation in the duplicate sample exceeded _+12 mg/dl for total cholesterol and triglycerides and • 6 mg/dl for HDL cholesterol. Total cholesterol was assayed by enzymatic procedures, 19 and the HDL cholesterol fraction was determined by the heparin/manganese chloride precipitation method. 2~LDL cholesterol fractions were calculated by means of Friedewalds' equation, and VLDL cholesterol fractions were calculated by means of measured triglyceride values. 21 Physical and nutritional evaluations. Body weight and percentage of body fat (anthropomorphic method using three circumferential measurements) were measured 22 as part of the pre- and post-training or control evaluations. Subjects were advised about the importance of not altering usual dietary patterns during the study period. In addition, a food frequency questionnaire that was validated at the Rockefeller University Lipid Research Unit and included alcohol consumption was completed at both valuation times. 23 Dietary recall (food frequency questionnaire) was repeated midway and at the end of the study. Exercise training. After the initial evaluation, subjects were randomly assigned to groups that would train at either 65% (13 subjects), 75% (14 subjects), or 85% (12 subjects) of the subjects' measured maximal heart rate or to a no-training control group (10 subjects). Subjects exercised three times a week for 30 minutes on cycle ergometers; an interval training protocol was used (4 minutes exercise load and 1 minute cool down). The exercise training period was 12 weeks. No subject missed more than three sessions. Pulse was monitored by laboratory assistants to ensure that achieved heart rates were within the assigned training limits. The control group, was instructed to continue their usual sedentary lifestyles during the study period. There
were no dropouts after initiation of the exercise or control position of the study. Statistical analysis. Pre- and post-training or control period data within specific groups were analyzed by means of a one- or two-tailed, dependent " t " test. Differences in post-training data among the groups were compared by means of analysis of covariance. Post hoc comparisons were evaluated by the Scheffe technique. 24 RESULTS Metabolic and anthropomorphic measurements. At the p r e s t u d y evaluation, the different intensity training and control groups were not significantly different (analysis of variance) with regard to age, b o d y weight, b o d y fat, a n d VQmax. T h e r e was no signific a n t change in pre- and p o s t s t u d y b o d y weight or b o d y composition (percentage of fat) in a n y of the groups t h a t exercised (Table I). T h e r e were no significant differences in preexercise food intake a m o n g groups, and there was no change in the types of food c o n s u m e d or the daily calorie intake as r e p o r t e d by our subjects. We observed significant i m p r o v e m e n t in aerobic capacity at all three levels of exercise intensity. u {Fig. 1) increased a m e a n of 3.1 m l / m i n / k g (p < 0.05)in the lower intensity exercise group (65 % m a x i m a l h e a r t rate), whereas in the higher intensity exercise groups aerobic capacity improved by a m e a n of 5.3 m l / m i n / k g (p < 0.05) in the 75% group and 10.5 m l / k g / m i n (p < 0.01) in the 85% group (Table
I). Plasma lipid and lipoproteins (Table II; Figs. 2, 3, and 4). Results of paired analysis of lipid profiles showed t h a t total cholesterol did not change significantly in a n y group; however, H D L cholesterol increased significantly in the 75 % and 85 % maximal h e a r t rate training groups (p < 0.01) but not in the 65 % or control group. L D L cholesterol decreased significantly only in the 75 % group (p < 0.05). N o significant dif-
Volume
119
Number 2, Part 1
Exercise intensity to cholesterol fractions
279
* p < .01
50
**
45
-[
40
p < .05
[~]
Pre-
[~
Post-
k
VO2MA X
55
~r
ml/kg/min 30 25 20 15
65
75
85
i[
CONTROl_
TRAINING INTENSITIES - % HRMAx Fig.
1. R e l a t i o n o f oxygen consumption to exercise intensity.
Table II. Plasma lipid and lipoprotein cholesterol levels (mg/dl) in control and three test groups before and after a
12-week exercise training period
Lipids Total cholesterol Before After Triglycerides Before After Lipoproteins V L D L cholesterol Before After L D L cholesterol Before After HDL cholesterol Before After
Control p
65% p
196.3 • 16 NS 205.6 • 24
214.7 • 17 (NS) 208.3 +- 12
216.9 _+ 11 NS 206.2 -+ 11
237.2 • 14 NS 241.8 • 19 NS
121.9 • 21 N S 126.6 • 28
116.4 • 13 N S 101.7 • 21
105.4 -+ 16 N S 109.1 • 21
113.5 • 23 NS 111.5 • 12
24.3 +_ 4 N S 25.3 • 6
23.2 • 3 N S 20.3 • 2
21.0 • 3 NS 20.8 • 4
22.8 • 5 NS 22.3 • 2
127.6 + 13 N S 135.7 • 18
144.3 • 16 N S 142.3 • 12
159.8 • 9
R i c h a r d A. Stein, MD, D o n a l d W. Michielli, P h D , M o r t o n D. Glantz, PhD, H y m a n Sardy, PhD, Arlette Cohen, PhD, Nieca Goldberg, MD, and Clinton D. Brown, MD. Brooklyn, N.Y.
T h e r e is an increasing b o d y of d a t a to s u p p o r t the direct relationship of low-density lipoprotein (LDL) cholesterol a n d the inverse relationship of high-density lipoprotein ( H D L ) cholesterol to risk of developing coronary a r t e r y disease. TM Modification of factors t h a t favorably reduce total serum cholesterol levels and favorably alter the ratio of H D L and L D L cholesterol is thus of great interest and the subject of continuing investigations3 -8 T h e role of exercise in altering lipoproteins has been studied with differing conclusions, 9-11 in p a r t explainable by differences in protocols a n d the absence of control groups. M a n y studies r e p o r t e d to date, however, have been poorly controlled with regard to the amount, duration, and intensity of the exercise performed. 12,14-17This s t u d y From the State Universityof New York-HealthScienceCenterat Brooklyn, and BrooklynCollege. Receivedfor publicationMarch 7, 1989;acceptedSept. 15, 1989. Reprint requests:RichardA. Stein,MD, SUNY-HealthScienceCenterat Brooklyn,450 ClarksonAve.,Brooklyn,NY 11203. 4/1/17361
determines the effect(s) of exercise training intensity on plasma lipids and lipoproteins and determines whether there is a threshold training intensity below which such salutary changes would not occur during a relatively short training period. METHODS Subjects. Forty-nine male faculty and staff members at
Brooklyn College were selected from among a larger pool of volunteers for inclusion in the study. The mean age was 44 _+ 8 years. Criteria for selection included a normal resting 12-lead ECG, no history or symptoms of cardiac disease, and no abnormalities in heart rate, ST segment, or blood pressure response during a symptom-limited maximal exercise ECG examination. Maximal exercise ECG studies. All subjects underwent maximal exercise ECG studies with continuous multilead ECG monitoring; a continuous cycle ergometer protocol was used (starting at a work load of 300 kpm and increasing by 100 kpm every 2 minutes). This was performed to exhaustion before and immediately after the exercise training or control period. Expired air was collected by means of open-circuit methodology,19 minute uptake con277
278
February 1990 American Heart Journal
Stein et al.
Table I. Comparison of body weight, percentage of body fat, and VO2max among control and three test groups before and after 12-week exercise training period Control ( N = 10)
Body weight (kg) Before 82.2 + 7.8 (NS) After 82.25 _+5.4 Body fat (%) Before 27.4 + 1.6 (NS) After 26.6 +_ 1.6 VO2m~ (ml/kg/min) Before 30.4 +_ 1.8 (NS) After 31.7 _+ 1.7
65 % ( N = 13)
75 % ( N = 14)
85 % ( N = 12)
70.5 _+ 2.8 (NS) 70.5 +_2.9
82.8 _+5.2 (NS) 82.6 _+5.1
84.4 _+8.2 (NS) 84.0 _+7.2
23.8 _+ 1.5 (NS) 23.7 _+ 1.5
26.8 _+0.5 (NS) 26.5 _+ 1.1
27.5 _+ 2.0
28.4 _+ 1.3 (p < 0.05) 31.5 _+ 1.5
30.3 _+ 1.3 (p < 0.05) 35.9 + 1.0
25.1 ___2.0 (p < 0.01) 35.9 + 3.8
28.4 +_ 2.1
(NS)
NS, Not significant.
sumption (V02) was measured, and maximal minute oxygen uptake (VO2max) was determined for each subject. Blood studies. Fasting morning blood samples were obtained from all subjects before and immediately after the exercise training or control period. Blood samples were drawn from the medial vein into tubes containing EDTA. Plasma was separated by centrifugation, and samples were stored at - 1 0 ~ C until assays were determined (within 48 hours) in all samples. All assays were done in duplicate or triplicate--in triplicate if variation in the duplicate sample exceeded _+12 mg/dl for total cholesterol and triglycerides and • 6 mg/dl for HDL cholesterol. Total cholesterol was assayed by enzymatic procedures, 19 and the HDL cholesterol fraction was determined by the heparin/manganese chloride precipitation method. 2~LDL cholesterol fractions were calculated by means of Friedewalds' equation, and VLDL cholesterol fractions were calculated by means of measured triglyceride values. 21 Physical and nutritional evaluations. Body weight and percentage of body fat (anthropomorphic method using three circumferential measurements) were measured 22 as part of the pre- and post-training or control evaluations. Subjects were advised about the importance of not altering usual dietary patterns during the study period. In addition, a food frequency questionnaire that was validated at the Rockefeller University Lipid Research Unit and included alcohol consumption was completed at both valuation times. 23 Dietary recall (food frequency questionnaire) was repeated midway and at the end of the study. Exercise training. After the initial evaluation, subjects were randomly assigned to groups that would train at either 65% (13 subjects), 75% (14 subjects), or 85% (12 subjects) of the subjects' measured maximal heart rate or to a no-training control group (10 subjects). Subjects exercised three times a week for 30 minutes on cycle ergometers; an interval training protocol was used (4 minutes exercise load and 1 minute cool down). The exercise training period was 12 weeks. No subject missed more than three sessions. Pulse was monitored by laboratory assistants to ensure that achieved heart rates were within the assigned training limits. The control group, was instructed to continue their usual sedentary lifestyles during the study period. There
were no dropouts after initiation of the exercise or control position of the study. Statistical analysis. Pre- and post-training or control period data within specific groups were analyzed by means of a one- or two-tailed, dependent " t " test. Differences in post-training data among the groups were compared by means of analysis of covariance. Post hoc comparisons were evaluated by the Scheffe technique. 24 RESULTS Metabolic and anthropomorphic measurements. At the p r e s t u d y evaluation, the different intensity training and control groups were not significantly different (analysis of variance) with regard to age, b o d y weight, b o d y fat, a n d VQmax. T h e r e was no signific a n t change in pre- and p o s t s t u d y b o d y weight or b o d y composition (percentage of fat) in a n y of the groups t h a t exercised (Table I). T h e r e were no significant differences in preexercise food intake a m o n g groups, and there was no change in the types of food c o n s u m e d or the daily calorie intake as r e p o r t e d by our subjects. We observed significant i m p r o v e m e n t in aerobic capacity at all three levels of exercise intensity. u {Fig. 1) increased a m e a n of 3.1 m l / m i n / k g (p < 0.05)in the lower intensity exercise group (65 % m a x i m a l h e a r t rate), whereas in the higher intensity exercise groups aerobic capacity improved by a m e a n of 5.3 m l / m i n / k g (p < 0.05) in the 75% group and 10.5 m l / k g / m i n (p < 0.01) in the 85% group (Table
I). Plasma lipid and lipoproteins (Table II; Figs. 2, 3, and 4). Results of paired analysis of lipid profiles showed t h a t total cholesterol did not change significantly in a n y group; however, H D L cholesterol increased significantly in the 75 % and 85 % maximal h e a r t rate training groups (p < 0.01) but not in the 65 % or control group. L D L cholesterol decreased significantly only in the 75 % group (p < 0.05). N o significant dif-
Volume
119
Number 2, Part 1
Exercise intensity to cholesterol fractions
279
* p < .01
50
**
45
-[
40
p < .05
[~]
Pre-
[~
Post-
k
VO2MA X
55
~r
ml/kg/min 30 25 20 15
65
75
85
i[
CONTROl_
TRAINING INTENSITIES - % HRMAx Fig.
1. R e l a t i o n o f oxygen consumption to exercise intensity.
Table II. Plasma lipid and lipoprotein cholesterol levels (mg/dl) in control and three test groups before and after a
12-week exercise training period
Lipids Total cholesterol Before After Triglycerides Before After Lipoproteins V L D L cholesterol Before After L D L cholesterol Before After HDL cholesterol Before After
Control p
65% p
196.3 • 16 NS 205.6 • 24
214.7 • 17 (NS) 208.3 +- 12
216.9 _+ 11 NS 206.2 -+ 11
237.2 • 14 NS 241.8 • 19 NS
121.9 • 21 N S 126.6 • 28
116.4 • 13 N S 101.7 • 21
105.4 -+ 16 N S 109.1 • 21
113.5 • 23 NS 111.5 • 12
24.3 +_ 4 N S 25.3 • 6
23.2 • 3 N S 20.3 • 2
21.0 • 3 NS 20.8 • 4
22.8 • 5 NS 22.3 • 2
127.6 + 13 N S 135.7 • 18
144.3 • 16 N S 142.3 • 12
159.8 • 9
