In Steve's last article he examined the effects of lower steady state training (UT2), the benefits of which come in the form of changes within the working muscle, enabling an efficient use of consumed oxygen. Prolonged low intensity training is heavily implicated in stimulating chronic changes such as the improved use of muscle fibre types, where 'fatigue resistance' seems to be the secret behind 'mileage' oriented programmes. But many endurance sports are putting up the effort to a minimum of 'upper steady state' or UT1 training . The question is why and is this the best thing to do?

U T 1 The lactate threshold is the point beyond which further increases in work result in the accumulation of lactate. This threshold (discussed further in Steve's next article) is the physiological measure most highly related to performance in rowing and other endurance events. The oxygen utilisation 1 (UTl) training band is defined as the heart rate zone that occurs approximately 10 beats below the lactate threshold.

The level of physiological stress is still relatively low and active athletes should be able to conduct UTl training for 40 minutes and up to 90 minutes when highly trained. However, this training intensity should not be easy. You should be conscious of your breathing, but feel comfortable and in control, not short of breath. Longer sessions are very demanding and you may need an easier day following sessions over 70 minutes.

Heart rate monitoring shows that UT1 training should take place at approximately 75-85% of maximum heart rate. During longer sessions the heart rate should start nearer to the bottom of the heart rate range, whereas for the shorter sessions you should aim for the top of the range. By doing this some allowance can be made for the fact that the heart rate will rise upwards, throughout a session, particularly in hot conditions.

This drift occurs as the body loses fluid, mainly through sweating. The fluid is lost from the working muscle and from the plasma component of blood. This makes the blood 'thicker' and harder to pump, hence the increase in heart rate for the same workload. For every 1% dehydration, heart rate drifts approximately 7 beats per minute. Therefore, in order to ensure that you are training within the correct zone, fluid intake must take place periodically. However, there is always some drift, and the best strategy to allow for this is to start exercising at the bottom of the range but finish near the top.

Whether athletes should perform more of their training at the UTl intensity rather than UT2 requires further clarification from scientific study. Certainly the muscles' physical, chemical and metabolic characteristics will be enhanced in the same way as UTZ training, but the extent to which the muscle adapts is not clear. These aerobic systems will be required to work at a higher level than during UT2 exercise, due to the greater requirement for oxygen to maintain a higher power output. This intensity will result in slightly higher lactate level than during UT2 work, but lactate should not accumulate.

The body adapts by improving the lactate clearance mechanisms, allowing greater power production before lactate begins to accumulate. This has important implications for performance due to the close relationship of the lactate threshold with success in endurance performance. Lactate during UT2 work is close to resting levels and so it is unlikely to be as effective for training the 'clearance of lactate' as UT1.

Extended periods of UTl training has the same effect as UT2 in the improved use of endurance muscle fibres and possible conversions to a more endurance type, but the shorter duration of exercise may limit this change. However, it must not be forgotten that the stress level is higher during UT1 work and its effect upon other systems such as immune and hormonal systems is still significant. In short UT1 training can be powerful stuff, and its use should be managed carefully.

It is for these reasons that several endurance sports including running and cycling have used the UT1 exercise intensity as the' mainstay for endurance training, in preference to the UT2 zone.

Some do not even consider the UT2 zone as worth a mention as a productive training stimulus (Martin and Coe, 1997) and others express quite strong views as to its use. Dr Andrew Jones a leading endurance physiologist, says 'Training at exercise intensities that produce heart rates more than 20 beats/min below the lactate threshold (i.e. UT2 training) is unlikely to produce meaningful improvements in aerobics fitness for activities other than ultra-endurance events'.

On balance it would appear that the endurance promoting effects of UTl training are more significant than those of UT2, for the reasons assbciated with resisting lactate accumulation. If training time is limited, then UTl training should definitely be the priority, whereas the full time athlete has additional time in which he/she has the 'luxury' of performing so.me longer UT2 work. I suggest that no single training zone in isolation provides the magic solution for improving endurance, considering that different kinds of training give a variety of different training stresses to the body. Such an approach would probably give the best results, but the priorities for training should be based upon individual differences and circumstances.

Editorial by Steve Ingham