Lactic acid build up is common in new exercisers. In time with regular training, you will eventually be able to use excess lactic acid as energy - rather than to slow you down.
Do make sure you have a long warm up and gradually build up your intensity. Work within your target heart rate and do not exceed your maximal heart rate zone.
- Stick to activities that are lower in impact initially.
When you start to feel a cramp coming on, slow down gradually and keep moving, as the working muscles will help to dissipate the acid build up.