Muscle cramping during exercise : causes, solutions and questions remaining

Muscle cramp is a temporary but intense and painful involuntary contraction of skeletal muscle that can occur in many different situations. The causes of, and cures for, the cramps that occur during or soon after exercise remain uncertain, although there is evidence that some cases may be associated with disturbances of water and salt balance, while others appear to involve sustained abnormal spinal reflex activity secondary to fatigue of the affected muscles. Evidence in favour of a role for dyshydration comes largely from medical records obtained in large industrial settings, although it is supported by one large-scale intervention trial and by field trials involving small numbers of athletes. Cramp is notoriously unpredictable, making laboratory studies difficult, but experimental models involving electrical stimulation or intense voluntary contractions of small muscles held in a shortened position can induce cramp in many, although not all, individuals. These studies show that dehydration has no effect on the stimulation frequency required to initiate cramping and confirm a role for spinal pathways, but their relevance to the spontaneous cramps that occur during exercise is questionable. There is a long history of folk remedies for treatment or prevention of cramps; some may reduce the likelihood of some forms of cramping and reduce its intensity and duration, but none are consistently effective. It seems likely that there are different types of cramp that are initiated by different mechanisms; if this is the case, the search for a single strategy for prevention or treatment is unlikely to succeed.Publisher PDFPeer reviewe

High-intensity non-invasive ventilation in stable hypercapnic COPD: Evidence of efficacy and practical advice

Patients with end-stage chronic obstructive pulmonary disease (COPD) frequently develop chronic hypercapnic respiratory failure (CHRF), with disabling symptoms and poor survival. The use of long-term nocturnal non-invasive ventilation (NIV) to treat CHRF in COPD has long been subject of debate due to conflicting evidence. However, since the introduction of high-intensity NIV (HI-NIV) in COPD, physiological and clinical benefits have been shown. HI-NIV refers to specific ventilator settings used for NIV aimed at achieving normocapnia or the lowest partial arterial carbon dioxide pressure (PaCO2 ) values as possible. This review will provide an overview of existing evidence of the efficacy of HI-NIV stable COPD patients with CHRF. Secondly, we will discuss hypotheses underlying NIV benefit in stable hypercapnic COPD, providing insight into better patient selection and hopefully more individually titrated HI-NIV. Finally, we will provide practical advice on how to initiate and follow-up patients on HI-NIV, with special emphasis on monitoring that should be available during the initiation and follow-up of HI-NIV, and will discuss more extended monitoring techniques that could improve HI-NIV treatment in the future