title: Low-frequency severe-intensity interval training improves cardiorespiratory functions.
abstract: OBJECTIVE
  The present study investigated the effects of severe-intensity interval training at a frequency of once a week on cardiorespiratory function at rest and during exercise.
  
  
  METHODS
  Fourteen young healthy males were randomly assigned to either an interval training group or control group. Cardiorespiratory function was investigated by incremental maximal exercise test and constant work rate submaximal exercise test before and after the intervention period in all subjects. Submaximal exercise test was conducted at two work rates (80% ventilatory threshold (VT) level and 100% VT level plus 50% of the difference between VT and peak oxygen consumption (V˙O2)) for 8 min; the same work rates and duration were used before and after training. Left ventricular adaptations were assessed by echocardiography under supine resting conditions before and after training. In the interval training group, seven subjects performed cycle ergometer training once per week for 3 months. The training consisted of three bouts of exercises to volitional fatigue at 80% maximum work rate.
  
  
  RESULTS
  Increased V˙O2max (+13%, P = 0.015), VT (+21%, P = 0.001), and left ventricular posterior wall thickness (+18%, P = 0.002) and reduced minute ventilation (-12%, P = 0.032) and blood lactate concentration (-16%, P = 0.025) during high-intensity exercise were observed after the training program compared with baseline. Although not significant, V˙O2 and cycling economy (V˙O2 per work rate) during high-intensity exercise decreased slightly after training.
  
  
  CONCLUSIONS
  The present results indicate that severe-intensity interval training, even when performed at a low frequency, markedly improves cardiorespiratory function as well as induces cardiac morphological adaptations involving left ventricular hypertrophy and cardiorespiratory metabolic response during submaximal exercise. The present findings may provide new insights for low-frequency, severe-intensity interval training in the field of sports science.
authors.affiliation: Graduate School of Health Sciences, Morinomiya University of Medical Sciences, Osaka City, JAPAN.
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Nakahara
authors.forename: Shin-Ya
authors.initials: SY
authors.lastname: Ueda
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Miyamoto
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D001642:Bicycling / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D005080:Exercise Test; D006352:Heart Ventricles / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption; D010806:Physical Education and Training / Q000379:methods*; D012143:Respiratory Physiological Phenomena; D013997:Time Factors; D014463:Ultrasonography; D055815:Young Adult
chemical_list: D019344:Lactic Acid