To get natural relief from muscle strain, use ice during the first 24 hours. This can be the difference between feeling fine in a few hours and being laid up for a week or two. Put ice into an icebag and put the ice on the hurting muscle - with a small towel between you and the icebag.
Leave the ice on for no more than 20 minutes at a time, alternating with no ice for 20 minutes (on, off, on, off) several times during the day. Using heat during the first 24 hours will increase swelling and cause more pain.
For an injury over 24 hours old: add two cups of natural apple cider vinegar to your bath water and soak for a half hour. The potassium in the vinegar helps the muscles.
From Natural First Aid Kit: Soak in a tub of very warm water, adding 10 to 15 drops of Rosemary Essential Oil to the water.
Note: Rosemary can be harmful if you are pregnant.