No matter how many biceps curls I do, I don't get definition at the front of my arms and they are very wobbly.

I don't recommend women do traditional biceps curls (weight in hand, bending at the elbow) with heavy weights. Any definition you do get will target the shorter, bulkier muscle of the biceps group of muscles.

If you seek a sleeker, leaner arm shape you need to target the long head of the biceps group. Work this by doing frontal raises: start with your arms straight down in front of you, palms facing away from thighs. Slowly lift your arms in front of you until they are level with your eye line, then lower. This is a simple exercise but these tips make the difference: keep elbows slightly soft and lightly grip the weight, keeping knuckles, wrist and elbow in line with the weight. Clenching the weight too slightly can increase blood pressure and recruits more muscle power from the lower forearms.

The pace is crucial - try four counts up and four counts down. The slower pace and using a longer arm will mean you need lighter weights. Unopened bottles of wine make excellent home weights: hold one bottle in each hand, with the cork end facing outwards. Complete 12-16 repetitions four to five times a week. Astanga yoga is also good for leaner definition, especially the sun salutation A and B series.

With any arm exercise, keep your neck long, focusing on the space between shoulders and ears. Tensing shoulders can detract from the targeted muscles and, with heavy weights, can contribute to a thickened neck - which, I anticipate, may not be the desired outcome of your efforts.

· Joanna Hall is a fitness expert (joannahall.com). Send your exercise questions to Weekend, 119 Farringdon Road, London EC1R 3ER (weekend@theguardian.com).