Eur J Appl Physiol (1991) 62:400-404 European Journal of
Applied
Physiology and Occupational Physiology © Springer-Verlag 1991
Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids Pekka Oja 1, Raija M. T. Laukkanen ], T. Katriina Kukkonen-Harjula 1, Ilkka M. Vuori ], Matti E. Pasanen t, Seppo P. T. Niittym~iki 2, and Tiina Solakivi 3 1 President Urho Kaleva Kekkonen Institute for Health Promotion Research, P.O. Box 30, SF-33501 Tampere, Finland 2 Tampere Research Station of Sports Medicine,Tampere, Finland 3 Universityof Tampere, Department of Biomedicine,Tampere, Finland Accepted January 22, 1991
Summary. Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n= 15 in study 1, n = 16 in study 2), running (n = 16 in study 1 and n = 16 in study 2) and control (n = 17 in study 1 and n = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9-10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%-85% of the maximal oxygen consumption (1202max) using portable heart rate metres and the mean heart rate was 156-157 beats.rain -1 in the training groups. In the pooled data of the two studies the mean increase in the I202 m a x (in ml.min -1 .kg -1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase in VO2m~x was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9-10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.
Key words: Endurance conditioning - Aerobic fitness Lipoproteins - Insulin
Introduction The physiological effects of running training on sedentary middle-aged men are well known, and they have also been compared with those of other types of exercise, such as walking, cycling and tennis (Pollock et al.
Offprint requests to: P. Oja
1975; Gettman et al. 1976; Wenger and Bell 1986). Few research data are available on the training effects of cross-country skiing on sedentary persons (see Eisenman et al. 1989). Cross-country skiing is an exercise which can be performed for several hours with high absolute and relative cardiovascular strain even by nonathletes (Vuori 1977; Oja et al. 1988). Skiing involves the muscles of the upper extremities and the trunk in addition to those of the legs. The rhythmic movement pattern allows rest for the muscles during "micropauses" (Christensen and H6gberg 1950). Experienced skiers use pendulum-like swinging movements resulting in high mechanical efficiency (Norman et al. 1985). The vertical lift of the body is small and the impulse forces directed to the joints are minimal. Elite cross-country skiers are characterized by exceptionally high aerobic power (Rusko and Rahkila 1981; Astrand and Rodahl 1986). If this characteristic results from training and not from selection, different explanations are possible, based at least partly on the biomechanics of skiing. The manageable quantity of skiing training could exceed that of other endurance sports (e.g. running), or the training stimulus could be qualitatively different. The large working muscle mass in skiing may require high cardiac output without overwhelmingly high peripheral resistance and thus provide an efficient training stimulus for cardiac output, which is probably the limiting factor of maximal aerobic power (Saltin 1986). If this were true, skiing training could result in a larger gain in maximal aerobic power than running training. At the same time metabolic adaptations may take place in a larger muscle mass in skiing than in running. This phenomenon might be reflected in a different magnitude of training-induced changes, for example, in serum lipids (Haskell 1986). The purpose of this study was to determine whether cross-country skiing and running training results in different effects on the cardiorespiratory response in maximal cycle ergometer exercise or on serum lipids of untrained middle-aged men, as studied using a controlled randomized design.
401
Methods This report describes two experiments carried out during two successive winters. In the following text the first experiment is referred to as study 1 and the second as study 2.
Selection of the subjects. The subjects were selected from 886 40year-old men taking part in periodic health examinations provided by the municipal health care system of the city of Tampere. After a screening of the records for contra-indicative diseases, 596 preliminary invitations containing a questionnaire were posted. Of the 342 respondents, 235 men were willing to participate in the training study. Of these, 132 were excluded because the questionnaire revealed medical contra-indications to exercise (chronic disease or medication, musculoskeletal disabilities). One-hundred-and-three apparently healthy untrained men were invited to a final screening. Their body mass, blood pressure and serum cholesterol were within normal limits, and they had been engaged in vigorous aerobic exercise less than twice a week during the previous year. After a medical examination and a submaximal cycle exercise test, 6 men were excluded because of ischaemic electrocardiographic abnormalities during the exercise test, and 1 man was excluded because of a high level of physical fitness. Thus 96 men (48 men in both investigations) were accepted for study. Experimental procedure. After an informed consent was obtained from the subjects, they were randomly allocated into a crosscountry skiing (15 men in study 1 and 16 in study 2), a running (16 men in both studies) or a control (17 men in study 1 and 16 in study 2) group. One subject in the skiing group of study 2 dropped out before the training started. During the training 1 subject in the skiing group of study 1 dropped out because of a training injury, and 1 subject in the control group in study 2 was excluded because of the appearance of an unspecified systemic illness. Therefore, the final data included 47 subjects in study 1 and 46 in study 2. Physiological measurements and blood samples were taken before and after the training. In addition a mid-training exercise test was performed for the prescription of the training intensity during the last half of the programme. Measurement of maximal oxyoen consumption. A cycle ergometer (electronically braked Siemens Elema RE 820, Rodby Elektronik AB, Enh6rna, Sweden) was used for the test. The baseline exercise test commenced at an intensity of 75 W and continued with increments of 25 W at 2-min intervals until the subject's maximum was reached. Expired air was continuously collected and analysed to calculate oxygen consumption 0)'02) and related variables, using an automatic metabolic analyser (Horizon V, Sensor Medics, Anaheim, CA, USA). The manufacturer's volume and gas calibration procedures were followed. For additional confirmation that peak effort was maximum, ratings of perceived exertion (RPE) were recorded on a 10-grade scale (Borg 1982) at the end of each 2-min stage, and a capillary blood sample was taken from the fingertip for lactate (la) analysis at 2-min intervals during the test, and at 2-min post-exercise in study 2. Training programme. The training lasted 9 weeks in study 1 and 10 weeks in study 2. There were three sessions each week, each session lasting 40 rain. The training intensity was set to correspond to 75%-85% of the maximal oxygen consumption (~702max)It was expressed as a target zone of the heart rate, which was determined for each individual from the regression line of the heart rate on the 1202 in the exercise test. The baseline exercise test was used to determine the training heart rate zone for the first half of the training and a mid-term exercise test was used for the same purpose for the second half. The heart rates during the exercise sessions were recorded with a portable telemetric heart rate metre (Sport Tester PE 2000, Polar Electro, Kempele, Finland). The RPE were recorded at the end of each exercise session. A capil-
lary blood sample was taken for the la determination at the end of one exercise session, in the middle and at the end of the training period. The subjects were introduced to nearby trails for skiing or roads for running. The diagonal skiing style was predominantly practised during the study. All the subjects had previous skiing experience. The subjects in training were advised not to engage in other exercise and to maintain their preprogramme dietary and smoking habits. The control subjects were asked to continue their usual dietary and smoking habits and to maintain their prestudy exercise routine, that is no more vigorous aerobic exercise than once a week. All subjects kept a log of their exercise during the study.
Biochemical analyses. The enzymatic UV-method (Boehringer Mannheim Diagnostica, Mannheim, Germany) was used for the la analysis. After overnight fasting venous blood samples were taken with the subject in a sitting position without a tourniquet. The samples were centrifuged and kept at - 7 0 ° C until the analyses. The serum total cholesterol (Nyegaard and Co A/S, Oslo, Norway), triglyceride (Boehringer Mannheim) and phospholipid (Boehringer Mannheim) concentrations were determined enzymatically in a Kone Olli-C analyser (Kone Ltd, Espoo, Finland). High-density lipoprotein (HDL) was separated by precipitation with polyethylene glycol (Izzo et al. 1981), and its cholesterol and phospholipid content was estimated using the same enzymatic methods. Low-density lipoprotein (LDL) was precipitated using heparin at pH 5.12 (Merck, Darmstadt, Germany). The LDL-cholesterol was calculated as the difference between the serum total cholesterol and the cholesterol content of the supernatant. The coefficient of variation for the between-day precision of the different fractions varied from 5.0% (total phospholipids) to 3.6% (HDL phospholipids). Serum insulin was analysed by radio-immunoassay (Novo Research, Copenhagen, Denmark). Statistical methods. The intensity of skiing and running training in study I and study 2 was compared statistically by Student's t-test with independent measures. An ANOVA with repeated measures was utilized to detect the training effects. In these analyses the data from study 1 and study 2 were pooled. For the estimated average changes in the I202.... the 95% confidence intervals were calculated.
Results There were 27 t r a i n i n g sessions s c h e d u l e d in s t u d y 1 a n d 30 in s t u d y 2. The m e a n a t t e n d a n c e varied f r o m 96% to 99% in the groups. I n s t u d y 1 the m e a n r e c o r d e d d u r a t i o n o f the t r a i n i n g session was 43.6 m i n , SD 1.4 in the skiing g r o u p a n d 40.1 min, SD 1.7 i n the r u n n i n g group. I n s t u d y 2 the m e a n session d u r a t i o n was bet w e e n 40 a n d 41 m i n for b o t h types o f t r a i n i n g . D u r i n g the t r a i n i n g p e r i o d s the daily m e a n t e m p e r a t u r e was - 4 ° C in s t u d y 1 a n d - 11 o C i n s t u d y 2. The m e a n t r a i n i n g heart rate was s i m i l a r in b o t h the skiing a n d r u n n i n g sessions, r a n g i n g f r o m 155 to 159 b e a t s . m i n -1 a n d c o r r e s p o n d i n g to 77%-82% o f the l)'O2max (Table 1). The m e a n o f the R P E i n skiing was lower t h a n that in r u n n i n g i n s t u d y 1. The m e a n capillary post-exercise la c o n c e n t r a t i o n d u r i n g t r a i n i n g was a p p r o x i m a t e l y 4 m m o l . 1- ] in b o t h studies. T h e m e a n b o d y mass o f the g r o u p s r a n g e d from 78.5 to 81.1 kg before the t r a i n i n g i n s t u d y 1 a n d from 76.3 to 80.9 kg in s t u d y 2. Over the p e r i o d o f t r a i n i n g the m e a n decrease in mass varied f r o m 0.3 to 1.7 kg in the e x p e r i m e n t a l groups, with n o s i g n i f i c a n t differences in the c h a n g e s a m o n g the groups.
402
The mean peak respiratory exchange ratio (R) was 1.16, SD 0.09, and the mean of the peak RPE was 8.4, SD 1.6, before the training in study 1. The corresponding values in study 2 were 1.12, SD 0.06, and 7.3, SD 2.2, respectively. Neither the peak R nor the peak RPE changed significantly during training in any group. In study 2 the mean peak capillary la concentration (either at the end of the maximal test or 2-min post-test) ranged between 8.4 and 10.6 mmol.1 -~ in the three groups and did not change significantly during the
a in m l . m i n - ~ . k g - 1 ; b n = 12; * P=0.02, significantly different from the corresponding running value
training. These data indicated that the peak effort in the maximal test remained unchanged during the training in both studies. The pre and posttraining means of the maximal cycle performance are shown for the pooled data in Table 2. The maximal power output (Wmax) increased significantly (P
Applied
Physiology and Occupational Physiology © Springer-Verlag 1991
Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids Pekka Oja 1, Raija M. T. Laukkanen ], T. Katriina Kukkonen-Harjula 1, Ilkka M. Vuori ], Matti E. Pasanen t, Seppo P. T. Niittym~iki 2, and Tiina Solakivi 3 1 President Urho Kaleva Kekkonen Institute for Health Promotion Research, P.O. Box 30, SF-33501 Tampere, Finland 2 Tampere Research Station of Sports Medicine,Tampere, Finland 3 Universityof Tampere, Department of Biomedicine,Tampere, Finland Accepted January 22, 1991
Summary. Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n= 15 in study 1, n = 16 in study 2), running (n = 16 in study 1 and n = 16 in study 2) and control (n = 17 in study 1 and n = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9-10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%-85% of the maximal oxygen consumption (1202max) using portable heart rate metres and the mean heart rate was 156-157 beats.rain -1 in the training groups. In the pooled data of the two studies the mean increase in the I202 m a x (in ml.min -1 .kg -1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase in VO2m~x was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9-10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.
Key words: Endurance conditioning - Aerobic fitness Lipoproteins - Insulin
Introduction The physiological effects of running training on sedentary middle-aged men are well known, and they have also been compared with those of other types of exercise, such as walking, cycling and tennis (Pollock et al.
Offprint requests to: P. Oja
1975; Gettman et al. 1976; Wenger and Bell 1986). Few research data are available on the training effects of cross-country skiing on sedentary persons (see Eisenman et al. 1989). Cross-country skiing is an exercise which can be performed for several hours with high absolute and relative cardiovascular strain even by nonathletes (Vuori 1977; Oja et al. 1988). Skiing involves the muscles of the upper extremities and the trunk in addition to those of the legs. The rhythmic movement pattern allows rest for the muscles during "micropauses" (Christensen and H6gberg 1950). Experienced skiers use pendulum-like swinging movements resulting in high mechanical efficiency (Norman et al. 1985). The vertical lift of the body is small and the impulse forces directed to the joints are minimal. Elite cross-country skiers are characterized by exceptionally high aerobic power (Rusko and Rahkila 1981; Astrand and Rodahl 1986). If this characteristic results from training and not from selection, different explanations are possible, based at least partly on the biomechanics of skiing. The manageable quantity of skiing training could exceed that of other endurance sports (e.g. running), or the training stimulus could be qualitatively different. The large working muscle mass in skiing may require high cardiac output without overwhelmingly high peripheral resistance and thus provide an efficient training stimulus for cardiac output, which is probably the limiting factor of maximal aerobic power (Saltin 1986). If this were true, skiing training could result in a larger gain in maximal aerobic power than running training. At the same time metabolic adaptations may take place in a larger muscle mass in skiing than in running. This phenomenon might be reflected in a different magnitude of training-induced changes, for example, in serum lipids (Haskell 1986). The purpose of this study was to determine whether cross-country skiing and running training results in different effects on the cardiorespiratory response in maximal cycle ergometer exercise or on serum lipids of untrained middle-aged men, as studied using a controlled randomized design.
401
Methods This report describes two experiments carried out during two successive winters. In the following text the first experiment is referred to as study 1 and the second as study 2.
Selection of the subjects. The subjects were selected from 886 40year-old men taking part in periodic health examinations provided by the municipal health care system of the city of Tampere. After a screening of the records for contra-indicative diseases, 596 preliminary invitations containing a questionnaire were posted. Of the 342 respondents, 235 men were willing to participate in the training study. Of these, 132 were excluded because the questionnaire revealed medical contra-indications to exercise (chronic disease or medication, musculoskeletal disabilities). One-hundred-and-three apparently healthy untrained men were invited to a final screening. Their body mass, blood pressure and serum cholesterol were within normal limits, and they had been engaged in vigorous aerobic exercise less than twice a week during the previous year. After a medical examination and a submaximal cycle exercise test, 6 men were excluded because of ischaemic electrocardiographic abnormalities during the exercise test, and 1 man was excluded because of a high level of physical fitness. Thus 96 men (48 men in both investigations) were accepted for study. Experimental procedure. After an informed consent was obtained from the subjects, they were randomly allocated into a crosscountry skiing (15 men in study 1 and 16 in study 2), a running (16 men in both studies) or a control (17 men in study 1 and 16 in study 2) group. One subject in the skiing group of study 2 dropped out before the training started. During the training 1 subject in the skiing group of study 1 dropped out because of a training injury, and 1 subject in the control group in study 2 was excluded because of the appearance of an unspecified systemic illness. Therefore, the final data included 47 subjects in study 1 and 46 in study 2. Physiological measurements and blood samples were taken before and after the training. In addition a mid-training exercise test was performed for the prescription of the training intensity during the last half of the programme. Measurement of maximal oxyoen consumption. A cycle ergometer (electronically braked Siemens Elema RE 820, Rodby Elektronik AB, Enh6rna, Sweden) was used for the test. The baseline exercise test commenced at an intensity of 75 W and continued with increments of 25 W at 2-min intervals until the subject's maximum was reached. Expired air was continuously collected and analysed to calculate oxygen consumption 0)'02) and related variables, using an automatic metabolic analyser (Horizon V, Sensor Medics, Anaheim, CA, USA). The manufacturer's volume and gas calibration procedures were followed. For additional confirmation that peak effort was maximum, ratings of perceived exertion (RPE) were recorded on a 10-grade scale (Borg 1982) at the end of each 2-min stage, and a capillary blood sample was taken from the fingertip for lactate (la) analysis at 2-min intervals during the test, and at 2-min post-exercise in study 2. Training programme. The training lasted 9 weeks in study 1 and 10 weeks in study 2. There were three sessions each week, each session lasting 40 rain. The training intensity was set to correspond to 75%-85% of the maximal oxygen consumption (~702max)It was expressed as a target zone of the heart rate, which was determined for each individual from the regression line of the heart rate on the 1202 in the exercise test. The baseline exercise test was used to determine the training heart rate zone for the first half of the training and a mid-term exercise test was used for the same purpose for the second half. The heart rates during the exercise sessions were recorded with a portable telemetric heart rate metre (Sport Tester PE 2000, Polar Electro, Kempele, Finland). The RPE were recorded at the end of each exercise session. A capil-
lary blood sample was taken for the la determination at the end of one exercise session, in the middle and at the end of the training period. The subjects were introduced to nearby trails for skiing or roads for running. The diagonal skiing style was predominantly practised during the study. All the subjects had previous skiing experience. The subjects in training were advised not to engage in other exercise and to maintain their preprogramme dietary and smoking habits. The control subjects were asked to continue their usual dietary and smoking habits and to maintain their prestudy exercise routine, that is no more vigorous aerobic exercise than once a week. All subjects kept a log of their exercise during the study.
Biochemical analyses. The enzymatic UV-method (Boehringer Mannheim Diagnostica, Mannheim, Germany) was used for the la analysis. After overnight fasting venous blood samples were taken with the subject in a sitting position without a tourniquet. The samples were centrifuged and kept at - 7 0 ° C until the analyses. The serum total cholesterol (Nyegaard and Co A/S, Oslo, Norway), triglyceride (Boehringer Mannheim) and phospholipid (Boehringer Mannheim) concentrations were determined enzymatically in a Kone Olli-C analyser (Kone Ltd, Espoo, Finland). High-density lipoprotein (HDL) was separated by precipitation with polyethylene glycol (Izzo et al. 1981), and its cholesterol and phospholipid content was estimated using the same enzymatic methods. Low-density lipoprotein (LDL) was precipitated using heparin at pH 5.12 (Merck, Darmstadt, Germany). The LDL-cholesterol was calculated as the difference between the serum total cholesterol and the cholesterol content of the supernatant. The coefficient of variation for the between-day precision of the different fractions varied from 5.0% (total phospholipids) to 3.6% (HDL phospholipids). Serum insulin was analysed by radio-immunoassay (Novo Research, Copenhagen, Denmark). Statistical methods. The intensity of skiing and running training in study I and study 2 was compared statistically by Student's t-test with independent measures. An ANOVA with repeated measures was utilized to detect the training effects. In these analyses the data from study 1 and study 2 were pooled. For the estimated average changes in the I202.... the 95% confidence intervals were calculated.
Results There were 27 t r a i n i n g sessions s c h e d u l e d in s t u d y 1 a n d 30 in s t u d y 2. The m e a n a t t e n d a n c e varied f r o m 96% to 99% in the groups. I n s t u d y 1 the m e a n r e c o r d e d d u r a t i o n o f the t r a i n i n g session was 43.6 m i n , SD 1.4 in the skiing g r o u p a n d 40.1 min, SD 1.7 i n the r u n n i n g group. I n s t u d y 2 the m e a n session d u r a t i o n was bet w e e n 40 a n d 41 m i n for b o t h types o f t r a i n i n g . D u r i n g the t r a i n i n g p e r i o d s the daily m e a n t e m p e r a t u r e was - 4 ° C in s t u d y 1 a n d - 11 o C i n s t u d y 2. The m e a n t r a i n i n g heart rate was s i m i l a r in b o t h the skiing a n d r u n n i n g sessions, r a n g i n g f r o m 155 to 159 b e a t s . m i n -1 a n d c o r r e s p o n d i n g to 77%-82% o f the l)'O2max (Table 1). The m e a n o f the R P E i n skiing was lower t h a n that in r u n n i n g i n s t u d y 1. The m e a n capillary post-exercise la c o n c e n t r a t i o n d u r i n g t r a i n i n g was a p p r o x i m a t e l y 4 m m o l . 1- ] in b o t h studies. T h e m e a n b o d y mass o f the g r o u p s r a n g e d from 78.5 to 81.1 kg before the t r a i n i n g i n s t u d y 1 a n d from 76.3 to 80.9 kg in s t u d y 2. Over the p e r i o d o f t r a i n i n g the m e a n decrease in mass varied f r o m 0.3 to 1.7 kg in the e x p e r i m e n t a l groups, with n o s i g n i f i c a n t differences in the c h a n g e s a m o n g the groups.
402
The mean peak respiratory exchange ratio (R) was 1.16, SD 0.09, and the mean of the peak RPE was 8.4, SD 1.6, before the training in study 1. The corresponding values in study 2 were 1.12, SD 0.06, and 7.3, SD 2.2, respectively. Neither the peak R nor the peak RPE changed significantly during training in any group. In study 2 the mean peak capillary la concentration (either at the end of the maximal test or 2-min post-test) ranged between 8.4 and 10.6 mmol.1 -~ in the three groups and did not change significantly during the
a in m l . m i n - ~ . k g - 1 ; b n = 12; * P=0.02, significantly different from the corresponding running value
training. These data indicated that the peak effort in the maximal test remained unchanged during the training in both studies. The pre and posttraining means of the maximal cycle performance are shown for the pooled data in Table 2. The maximal power output (Wmax) increased significantly (P
