The muscles of the thigh and hamstring have opposing actions, but both are essential in running, be it sprinting or jogging. The thigh muscles, primarily the quadriceps, extend the leg at the knee, while the hamstring muscles, or biceps femoris, flex the leg at the knee. Both are under great stress when you're running, as they each flex and relax some 1,500 times per mile. When you suffer soreness or injury as a result, these muscles may require external support.
Causes of Thigh Pain
Most pain in the the thigh that results from running involves one of the four quadriceps muscles -- the three vasti and the rectus femoris, the latter being the most commonly injured. Pain in the front or "meat" of the thigh can be caused by simply running faster than you're used to or running downhill, in which case the soreness sets in a day or so after your workout and is usually bilateral. In contrast, a muscle pull or tear is typically found in only one leg. Pain on the outside aspect of the thigh often signals iliotibal band syndrome, or ITBS.
Causes of Hamstring Pain
Hamstring pain is very common in sprinters, as the three muscles that comprise the hamstrings -- the biceps femoris, semimembranosus and the semitendinosus -- contract forcefully and move through a greater-then-usual range of motion when you are running close to your maximum speed. As with the thigh muscles, when you have pain in both hammies the day after a set of sprints or vigorous drills involving rapid leg flexion, you're probably just sore as a result of doing something unfamiliar. If you have pain only on one side, you likely have a pull or a slight tear.
If you experience the sudden onset of moderate to severe thigh pain during a workout, stop running immediately. If the pain is mild and has a more gradual onset, you can keep running at a reduced speed and intensity. As soon as you can, apply a cold pack, a sandwich bag filled with ice or a wet towel to the affected area for 15 minutes, take an anti-inflammatory drug such as ibuprofen or naproxen according to the directions on the label, and wrap an ACE bandage around your thigh for support. Re-apply the ice pack every two to three hours. Absent a complete muscle tear, you can continue to run easily and stretch lightly in the days following the onset of pain. Once you are fully healed, doing strengthening and stretching exercises to reduce the likelihood of a recurrence is a good idea.
The initial remedy for hamstring pain is similar to that for thigh pain and most other soft-tissue injuries -- cessation of exercise, icing as soon as possible and every two to three hours thereafter, anti-inflammatory medication and a compression wrap for support. In contrast to a quadriceps pull or tear, however, you should be careful about stretching a wounded hamstring, instead relying on gentle running to help tease the muscle through a modest range of motion as a means of promoting healing. If you are able to run without serious discomfort, you'll want to take shorter steps than usual and avoid any kind of remotely intense running, especially sprinting you should also confine yourself to soft, flat surfaces until the pain abates completely.
L.T. Davidson has been a professional writer and editor since 1994. He has been published in "Triathlete," "Men's Fitness" and "Competitor." A former elite cyclist with a Master of Science in exercise physiology from the University of Miami, Davidson is now in the broadcast news business.