Q. Sometimes when I'm lifting weights I can feel my muscles 'shaking' and after some sessions they twitch intermittently. What is this?
One of the key points here is that it is entirely normal for muscles to twitch - called fasciculation by doctors - after serious exercise, especially following resistance work with weights or machines.
Heavy leg pressing, high-intensity weight training and intense routines are more likely to trigger it rather than low-intensity or lighter weights work, and this is usually a sign that the muscles have been worked intensively or past their normal levels of endurance. However, many people find that bench presses, pull-ups or even press-ups can also trigger muscle twitching. Most cases do not occur actually during the exercise - although this is quite possible - but afterwards, during rest, once any aerobic exercise is over.
The cause of muscle twitching during or after exercise is not entirely clear but one definite factor is lactic acid. If this builds up during exercise, it can then remain in muscles causing them to sporadically fire off and twitch when at rest.
If the muscles are used, however, this often seems to dilute its effect and the twitching stops or is less noticeable. Another strong contender is that the motor neurones in the affected muscle remain highly sensitive from an exercise session and so need time to calm down to normal.
Even though almost all cases of this are harmless there are ways to help minimise the chances of them occurring. One anecdotal tip that many patients tell me works is to try to eat a diet rich in antioxidant foods such as fresh fruit and vegetables - these may help to balance out some of the chemical changes that occur in muscles during exercise.
Try to allow at least 48 hours between resistance workouts of the same body part - vary your training routine so the same muscles are not being worked every day.
Stay well hydrated both during and after a training session and consider using an isotonic drink rather than plain water to replenish fluid lost through sweating.
Finally, remember that rest is as important to muscle conditioning as hard exercise so give yourself a day off when you need one.
Dr Roger Henderson (www.doctorhenderson.co.uk) qualified from St Bartholomew's Hospital in 1985 and became a GP in 1990. He is now the senior partner in a general practice and is medical columnist for the Sunday Times and NetDoctor.com. He has a keen interest in sports medicine and has run a number of marathons.