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Endurance Training: High Intensity Interval Training (HIT)
Amongst well-trained athletes additional improvements in aerobic fitness - above those brought about through aerobic base training - may only occur when training intensity is increased, in the form of high intensity interval training sessions at 90-100% of VO2max (Acevado and Goldfarb, 1989; Billat et al., 1999; Stepto et al., 1999). Training at this level leads to improvements in: both the aerobic and anaerobic energy pathways, improved oxygen transport, improved lactic acid clearance, Improved Lactate Threshold (LT), and improved Speed and neuromuscular co-ordination. Training at this level is particularly effective at improving the Lactate threshold, VO2max, and economy of motion.
Examples of HIT Sessions for runners: 5x2000m at 10k pace, 60 sec jog recovery 4x1600m at 5k pace, 90 sec jog recovery 5x1000m at 3k pace, 3min jog recovery The amount of HIT sessions that can be undertaken is limited due to an increased risk of overtraining. This is because training to often at these high levels will lead to increased levels of stress hormones. Research has shown that when HIT sessions were increased to three times per week, there were increases in the level of norepinephrine (a stress hormone) amongst the athletes, indicating an increased risk of overtraining (Billat et al., 1999). It is generally recommended that HIT sessions should make up 5-10% of total training volume (Daniels, 1998; Bompa, 1999; Neumann et al., 2000). You should perform no more than two HIT sessions per week if you want to reduce your risk of overtraining.
1) Interval level 1: 90 - 100%VO2max Performed at between 90 and 100%VO2max (85-95%HRmax), training at Level 3 intensities places a high level of stress on the musculature and physiologic systems and results in a steady rise in blood lactate concentrations (Fallowfield and Wilkinson 1999). Interval training involves repeated bouts of high intensity exercise (equal to or superior to the maximal lactate steady state velocity) interspersed with recovery periods (Billat, 2001). With highly trained athletes High-intensity interval training can lead to improvements in performance and blood lactate concentration independently of changes in their VO2max (Acevado and Goldfarb 1989; Londere 1997). Intense training at between 90-100% VO2max led to improved performance and reduced blood lactate, at the intensity of the increased training (Acevado and Goldfarb, 1989). Following the increased intensity training, the athletes were able to race at a higher %VO2max for the same lactate concentration. Training at 90-100% V02max (10K-5K pace) may be particularly important for improving running economy, since it has been suggested that training speed may influence running economy (Daniels, 1985; Fallowfield and Wilkinson, 1999). Franch et al., (1998) found that continuous distance training and long interval training led to improved RE at speeds close to the training intensity but shorter intervals run at faster speeds did not have a significant effect on RE at the slower speeds. When training at this level keep the recoveries short (no more than 1/5th of the length of the effort.
2) Interval Level 2: vVO2max Training Training at the vVO2max – which involves training at the minimum speed that elicits VO2max – has been shown to provide a powerful training stimulus (Billat et al., 1999; Smith et al., 1999). The use of one interval session per week at the velocity that VO2max occurs, over a four week period, with intervals run for 50% of the time that can be sustained at the VO2max (tlimvVO2max), led to a 3% improvement in vVO2max and a 6% improvement in running economy (Billat et al., 1999). Smith et al., (1999), suggested that using 60-75% Tmax (Time limit at VO2max) appears to provide a greater stimulus and may prove a valuable tool in exercise prescription. This training appears to provide a powerful stimulus to improve neuromuscular co-ordination. It is not clear whether an athletes individual Tmax needs to be established, or whether, simply performing repetitions of a set duration might be equally useful when performed at vVO2max. The uniform improvement seen across the range of athletes in the study by Smith et al. (1999) appears to suggest that the %Tmax utilised may be an important training stimulus. Hill and Rowell. (1997) found the time needed to reach VO2max varied between subjects and there was considerable variation in the time sustained at VO2max. Billat et al., (2000) demonstrated that the use of 30 second intervals at vVO2max alternated with 30 seconds at 50%vVO2max allowed the subjects to sustain an additional 5minutes at tlim VO2max, than during a continuous run to exhaustion. This method may prove particularly beneficial to some individuals since four of the eight subjects were able to sustain greater than ten minutes at VO2max with one subject sustaining 18 minutes at VO2max. The effect of exercise to rest ratio may also have a significant effect on the VO2max attained and blood lactate response during short intermittent runs at close to or above the vVO2max (Ballor and Volovsk, 1992). The use of a work to rest ratio of 2:1 at 90% VO2maxcaused a significantly greater oxygen uptake than a work to rest ratio of 1:1 at 110% VO2max with both having similar lactate responses (Ballor and Volovsk, 1992). Because of the short time response to this training, 4 weeks (Billat et al., 1999; Smith et al 1999), this training may prove useful if utilised 4-6 weeks prior to a major competition as a final training stimulus.
Examples of this type of training:
3) Interval Training at speeds greater than vVO2max When training intensities are greater than 100% VO2max there is a strong anaerobic component, and hence, high levels of lactate accumulate in the muscles and blood stream. A greater emphasis is placed on recovery so as to maintain the quality of efforts. Because of the high intensity duration of intervals are kept short and normally would last no longer than 90 seconds. There is limited research with regard to the effect of intense anaerobic intervals with regard to endurance performance. Hawley et al. (1997) found that the inclusion of 12, 30 second, work bouts at 175% PP (the peak power sustained in a max test) led to a substantial enhancement of performance with improved 40-km time trial cycling performance. The author speculated that this improvement may have been due to improved buffering capacity that would allow a greater amount of work to be performed. The use, of work intervals at 110% VO2max, nearly doubled the plasma lactate levels (Ballor and Volovsek, 1992). The use of 20 s of rest per minute at the 110% VO2max was not enough to allow effective metabolism of the lactate and production was in a non steady state. This method of training, often referred to as lactate stacking, since blood lactate increases with each work interval, may lead to increased buffering capacity since the last five minutes of exercise were performed at a blood lactate of greater than 8.0mmol.l-1. It appears that training at intensities that are greater than the VO2max, may prove a useful tool as final preparation for an endurance event by increasing the muscle buffer capacity. It has not been established what the time course of the adaptation is. But since the increases in blood buffering capacity are likely to occur fairly rapidly this type training could be used over the last 2-3 weeks prior to a major competition.
Examples of this type of training: 10x60 seconds effort (max effort), 30 seconds recovery (easy pace) 15x40 seconds effort (max effort), 20 seconds recovery (easy pace) 20x30 seconds effort (max effort), 15 seconds recovery (easy pace)
Acevado, E.O. and Goldfarb, A.H. (1989). Increased training intensity effects on plasma lactate, ventilatory thresholds, and endurance. Medicine and Science in Sports and Exercise. 21, 563-568. Billat, V.L., Flechet, B., Petit, B., Muriaux, G. and Koralsztein, J-P. (1999). Interval training at VO2max: effects on aerobic performance and overtraining markers. Medicine and Science in Sports and Exercise. 3 (1), 156-163. Billat, V.L., Slawinski, J., Bocquet, V., Demarle, A., Lafitte, L., Chassaing, P. and Koralsztein, J-P. (2000). Intermittent runs at the velocity associated with maximal oxygen uptake enables subjects to remain at maximal oxygen uptake for a longer time than intense but submaximal runs. European Journal of Applied Physiology. 81, 188-196. Billat, V.L. (2001). Interval training for Performance: a Scientific and Empirical Practice. Sports Medicine. 31 (1), 13-31. Daniels, J.T. (1985). A physiologist’s view of running economy. Medicine and Science in Sports and Exercise. 17 (3), 332-338. Fallowfield, J.L. and Wilkinson, J.L. (1999). Improving sports performance in Middle and Long-Distance Running. Chichester: John Wiley and Sons, LTD. Franch, J., Madsen, K., Djurhuus, M.S. and Pedersen, P.K. (1998). Improved running economy following intensified training correlates with reduced ventilatory demands. Medicine and Science in Sports and Exercise. 30 (8), 1250-1256. Hawley, J.A., Myburgh, K.H., Noakes, T.D. and Dennis, S.C. (1997). Training techniques to improve fatigue resistance and enhance endurance performance. Journal of Sports Sciences. 15, 325-333. Hill, D.W. and Rowell, A.L.(1997). Responses to exercise at the velocity associated with VO2max. Medicine and Science in Sports and Exercise. 29 (1), 113-116. Londeree, B.R. (1997). Effect of training on lactate/ventilatory thresholds: a meta analysis. Medicine and Science in Sports and Exercise. 29, 837-843. Smith, T.P., McNaughton, L.R. and Marshall, K.J. (1999). Effects of 4-wk training using Vmax/Tmax on VO2max and performance in athletes. Medicine and Science in Sports and Exercise. 31 (6), 892-896. |
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