For the personal trainer one of the biggest challenges is to identify the best means of monitoring intensity and performance. Objective measures, such as weight lifted, speed and distance run are important, but are unable to provide much information regarding physiological changes and sensations experienced by the exerciser. To this end, there are a number of approaches to monitoring exercise intensity and performance. These range from complex laboratory-based assessments to the use of simple question and answer procedures.
Before discussing examples of assessments however, it is important to point out that they are typically applied to activities that involve the lactate and aerobic energy systems. Monitoring internal changes during the 6 second bouts of activity associated with the CP system would prove difficult. It would appear therefore, that simple measures such as, levels of force or power generated are more appropriate for this system.
Lactate testing
It was noted earlier that levels of lactic acid provide a useful gauge as to the amount of anaerobic activity going on in the muscles. Measurement protocols typically use activities involving large muscle groups, such as running or cycling (results will differ depending on the activity being tested, thus the principle of specificity must be taken into account when selecting the mode of exercise).
Subjects are then required to perform exercise of incrementally increasing intensity. This either takes the form of a single sustained bout of exercise activity which ends when the subject can do no more (e.g. VO2max test), or a series of increasingly intense bouts of exercise (typically 4 minutes long) followed by short recovery periods. In both protocols, blood lactate responses are measured through blood analysis and the key changes in lactate response are noted. These relate to the point at which lactic acid first starts to accumulate and the point at which lactate accumulation becomes greater than its removal.
The value of this form of assessment is that the information gained serves as a useful indicator of current training status and as a predictor of endurance-based performance. Furthermore, it can be used to establish the optimum intensity for training (McArdle et al, 2001).
Researchers may argue about the finer points of this form of assessment, however from the point of view of the trainer the main difficulty is that it is impractical to administer in a ‘real’ training setting. In practice, lactate measurement is still largely confined to the laboratory environment. In the field setting, the trainer must consider using simpler procedures.
Heart rate monitoring
Since the development of the wireless heart rate monitor, monitoring heart rate during exercise has become easy and affordable. The predictability of the heart rate response (i.e. it goes up when we exercise and down when we rest), coupled with strong correlations with other physiological measures, such as oxygen consumption, make it an extremely useful measure of performance and exercise intensity.
Most modern cardiovascular machines will provide exercise intensities based upon predicted heart rate responses. The typical example of this being the aerobic training zone, which is taken to be between 60 - 90% of one’s maximum heart rate (220 – age) or 50 – 85% of one’s VO2max. Thus for a thirty year old client the calculation would be the following:
MaxHR: 220 – 30 = 190 beats/ min
60% of MaxHR: 190 * 0.6 = 114 beats/ min 90% of MaxHR: 190 * 0.9 = 171 beats/ min
The recommended aerobic training zone, therefore, for this client would be between 114 and 171 bpm. The calculation is relatively straight forward and with the use of a heart rate monitor it would be relatively easy to stay within prescribed training zones.
One of the drawbacks with heart rate monitors concerns the assumption that heart rate response is the same for everyone. Evidence suggests that although individual heart rate responds in a predictable manner, the magnitude of the response may differ from person-to-person. For example, women will generally have higher exercise heart rates than men (Wilmore and Costill, 2004). Also, research findings reported by McArdle et al (1992) clearly show that individuals of similar ages performing identical activities can have significantly different heart rate responses.
Whilst some of these variations could be attributed to differing levels of fitness, it is important to acknowledge the influence of genetic variations in heart rate response. In this respect, methods of monitoring intensity based on more individualised responses to exercise have proved extremely valuable.
Rating of perceived exertion (RPE)
In contrast to the methods described previously, RPE (also known as the Borg scale, after its creator - Gunnar Borg, 1998) is a subjective rating of how hard the exerciser feels they are working. Typically two scales have been used; either the 6 – 20 scale (6 = no exertion at all, 20 = maximal exertion) or a simplified 1 – 10 scale. Either way, research has indicated that when used correctly the scale provides an accurate measure of exercise intensity and seems to correlate well with other physiological measures of performance (Weltman, 1995; Wilmore and Costill, 2004). It is also extremely easy to administer. Perhaps the only real draw back with the measure is that it relies on the client being truthful about how hard an activity is!
The talk test
As with RPE the talk test relies on the response of the exerciser. Simply put, it identifies the exercise intensity at which ‘normal’ speech can no longer be sustained, which is indicative of the increased breathing rate triggered by exercise activity. Interestingly enough, the response is closely linked to the on-going physiological processes. The breathing rate is dictated by the volume of circulating gases in the blood which, in turn is directly determined by the level of work being undertaken by the muscles. Apart from being very simple to administer, reported research has also indicated that the talk test relates well to other measures of intensity (ACSM, 2004).
Metabolic equivalents (METs)
Another method of monitoring exercise intensity uses measures referred to as metabolic equivalents (METs). These are based on multiples of an individual's resting oxygen consumption. According to Wilmore and Costill (2004), at rest the average individual will consume approximately 3.5 ml of oxygen per kg of their body mass. This is the equivalent of 1.0 MET, thus energy expenditure at rest is 1.0 MET. Increases in activity levels will lead to elevated oxygen consumption and therefore, the number of METs will increase. Walking for example, will consume approximately three times the oxygen as resting metabolism, therefore, is the equivalent of 3.0 METs. Running flat out for a couple of minutes on the other hand, could be rated as high as 30.0 METs.
Tables of activities and their MET equivalents are readily available, thus the MET system is a useful guide for selecting exercise intensities rather than monitoring them. It is noted, however that the MET system is unable to take into account variations in environmental conditions and changes in physical fitness (Wilmore and Costill, 2004), thus it may be best combined with other methods of monitoring exercise intensity.
Over the years ‘core training’ or more specifically ‘core stability training’ has become extremely popular, both in the mainstream gym and sports training environments. The development of a strong and stable core is championed by many as the key to improved/pain free function and sporting excellence. Understanding static and dynamic posture has also become a needed area of understanding in trying to promote sound functional movement. There are a number of areas that must be considered in gaining a complete and well balanced understanding of this controversial and often misunderstood area:
• the structures that make up the core • the function of the core
• core activation as the foundation to good posture • what equipment is commonly used in core training • exercise prescription