The NICE Guidelines appear superficially reasonable but because they fail to mention either the seriousness of too much exertion and fail to offer any guidance on how to determine whether or not a person needs to rest more or has the physical functional capacity to be more active and or tolerate exposure to more exertional triggers they fail the ME/CFS community. The sad thing is that the research of Workwell et al has not been validated and extended. People are rightly concerned about harm caused by 2 day CPET tests. However, the key to improving health is not the 2 day CPET test, rather it is staying under anaerobic threshold and resting hard within 10% of morning resting heart rate. These 2 things are enabling people to improve. Limited research has been done regarding the limits of energy metabolism but Workwell et al have found an abnormally low anaerobic threshold and worldwide patients are observed to exceed their anaerobic threshold frequently. Athletes need to push themselves to reach the limits of their energy metabolism. However, people with ME/CFS reach and exceed these limits on a daily basis. All people with ME/CFS really need is for standard exercise physiological measures to be applied to them e.g. exercise/carry out daily activities at what is regarded as low intensity exercise e.g. 30% age predicted maximum..... Seriously - how many people with ME/CFS can get their HR's that low. Our problem appears to be that exercise physiology has NOT been applied to people with ME/CFS. Instead of experts in physiology looking at our heart rate abnormalities we have had mental health people tell us we are physically healthy and/or heart rate abnormalites are due to anxiety.