The present study compared the effects of aerobic endurance training at different intensities and with different methods matched for total work and frequency.
JAN HELGERUD, KJETILL HØYDAL, EIVIND WANG, TRINE KARLSEN, PÅL BERG, MARIUS BJERKAAS, THOMAS SIMONSEN, CECILIES HELGESEN, NINAL HJORTH, RAGNHILD BACH, and JAN HOFF
It is important to know how different training intensities influence adaptations in physiological parameters when selecting an optimum training regimen for a specific sport or for improving fitness in the general community. Cardiorespiratory endurance haslong been recognized as one of the fundamental components of physical fitness. Becauseaccumulation of lactic acid is associated with skeletal muscle fatigue, anaerobic metabolism cannot contribute at a quantitatively significant level to the energy expended. Pate and Kriska have described a model that incorporates the three major factors accounting for interindividual variance in aerobic endurance performance: maximal oxygen uptake (VO2max), lactate threshold, and work economy. Thus, the model should serve as a useful framework for comprehensive examination of the effects of aerobic training on endurance performance.
VO2max is probably the single most important factor determining success in an aerobic endurance sport and the strongest predictor for cardiovascular health and mortality. Thus, the present study compared the effects of aerobic endurance training at different intensities with different methods matched for total work and frequency. Responses in VO2max, stroke volume of the heart, blood volume, lactate threshold and running economy were examined.
Forty healthy, nonsmoking, moderately trained male subjects were randomly assigned toone of four groups. The average age, height, and weight of the 40 participating subjects were 25 years, 182 cm, and 82 kg, respectively. The four groups were: 1) long slow distance (70% maximal heart rate; HRmax); 2) lactate threshold (85% HRmax); 3) 15/15 interval running (15 s of running at 90–95% HRmax followed by 15 s of active resting at 70% HRmax); and 4) 4 x 4 min of interval running (4 min of running at 90–95% HRmax followed by 3 min of active resting at 70% HRmax). All four training protocols were matched for total work and were performed 3 days a week for 8 weeks.
High aerobic intensity interval training resulted increased VO2max compared with long slow distance and lactate threshold training. The percentage increases for the 15/15 and 4 x 4 min groups were 5.5 and 7.2%, respectively. The stroke volume of the heart increased by 10%, but only after interval training.
Conclusion: The major novel finding of this research is that high aerobic intensity endurance training is significantly more effective than moderate- and low-intensity training in improving VO2max. The increases in VO2max seem to be a result of increased pumping capacity of the heart. In all the training groups running economy improved. Although both the 15/15 training group and the 4 x 4 min training group improved VO2max, the 4x4 min group increased stroke volume of the heart significantly more. The 47 repetitions of 15 x 15 s training are also difficult to administer. Interval training with longer intervals, like the 4 x 4 min training is thus recommended to improve VO2max.