Interval Training Burns More Fat, Increases Fitness, Study Finds

Interval Training Burns More Fat, Increases Fitness, Study Finds

A Few 30 Second Sprints As Beneficial As Hour Long Jog

A Few 30 Second Sprints As Beneficial As Hour Long Jog

Interval Training Burns More Fat, Increases Fitness, Study Finds

Interval Training Burns More Fat, Increases Fitness, Study Finds

High-intensity interval training is time-efficient and effective, study suggests

High-intensity interval training is time-efficient and effective, study suggests

Training techniques to improve endurance exercise performances.

Kubukeli ZN, Noakes TD, Dennis SC.

Medical Research Council/University of Cape Town Research Unit on Exercise Science and Sports Medicine, Sports Science Institute of South Africa, Newlands, Cape Town, South Africa. zuko@worldonline.co.za

In previously untrained individuals, endurance training improves peak oxygen uptake (VO2peak), increases capillary density of working muscle, raises blood volume and decreases heart rate during exercise at the same absolute intensity.

In contrast, sprint training has a greater effect on muscle glyco(geno)lytic capacity than on muscle mitochondrial content. Sprint training invariably raises the activity of one or more of the muscle glyco(geno)lytic or related enzymes and enhances sarcolemmal lactate transport capacity.

Some groups have also reported that sprint training transforms muscle fibre types, but these data are conflicting and not supported by any consistent alteration in sarcoplasmic reticulum Ca2+ ATPase activity or muscle physicochemical H+ buffering capacity.

While the adaptations to training have been studied extensively in previously sedentary individuals, far less is known about the responses to high-intensity interval training (HIT) in already highly trained athletes.

Only one group has systematically studied the reported benefits of HIT before competition. They found that >or=6 HIT sessions, was sufficient to maximally increase peak work rate (W(peak)) values and simulated 40 km time-trial (TT(40)) speeds of competitive cyclists by 4 to 5% and 3.0 to 3.5%, respectively.

Maximum 3.0 to 3.5% improvements in TT(40) cycle rides at 75 to 80% of W(peak) after HIT consisting of 4- to 5-minute rides at 80 to 85% of W(peak) supported the idea that athletes should train for competition at exercise intensities specific to their event.

The optimum reduction or 'taper' in intense training to recover from exhaustive exercise before a competition is poorly understood. Most studies have shown that 20 to 80% single-step reductions in training volume over 1 to 4 weeks have little effect on exercise performance, and that it is more important to maintain training intensity than training volume.

Progressive 30 to 75% reductions in pool training volume over 2 to 4 weeks have been shown to improve swimming performances by 2 to 3%. Equally rapid exponential tapers improved 5 km running times by up to 6%.

We found that a 50% single-step reduction in HIT at 70% of W(peak) produced peak approximately 6% improvements in simulated 100 km time-trial performances after 2 weeks.

It is possible that the optimum taper depends on the intensity of the athletes' preceding training and their need to recover from exhaustive exercise to compete. How the optimum duration of a taper is influenced by preceding training intensity and percentage reduction in training volume warrants investigation.

1: Sports Med. 2002;32(8):489-509.

Aerobic High-Intensity Intervals Improve VO2max More Than Moderate Training

Aerobic High-Intensity Intervals Improve VO2max More Than Moderate Training.

Medicine & Science in Sports & Exercise. 39(4):665-671, April 2007.

JAN HELGERUD; KJETILL HØYDAL; EIVIND WANG; TRINE KARLSEN; PÅLR BERG; MARIUS BJERKAAS; THOMAS SIMONSEN; CECILIES HELGESEN; NINAL HJORTH; RAGNHILD BACH; JAN HOFF

Abstract:

Purpose:

The present study compared the effects of aerobic endurance training at different intensities and with different methods matched for total work and frequency. Responses in maximal oxygen uptake (VO2max), stroke volume of the heart (SV), blood volume, lactate threshold (LT), and running economy (CR) were examined.

Methods:

Forty healthy, nonsmoking, moderately trained male subjects were randomly assigned to one of four groups:

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);

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 resulted in similar total oxygen consumption and were performed 3 dwk-1 for 8 wk.

Results:

High-intensity aerobic interval training resulted in significantly increased VO2max compared with long slow distance and lactate-threshold training intensities (P <>

The percentage increases for the 15/15 and 4 x 4 min groups were 5.5 and 7.2%, respectively, reflecting increases in VO2max from 60.5 to 64.4 mLkg-1min-1 and 55.5 to 60.4 mLkg-1min-1.

SV increased significantly by approximately 10% after interval training (P < 0.05).

Conclusions:

High-aerobic intensity endurance interval training is significantly more effective than performing the same total work at either lactate threshold or at 70% HRmax, in improving VO2max. The changes in VO2max correspond with changes in SV, indicating a close link between the two.

(C) 2007 The American College of Sports Medicine