
Although there could be many causes, a hamstring problem like this can be an area of hypoxia (low oxygen delivery), calcium leakage, or scar tissue from a past injury.
Initial management for 48-72 hours after feeling this injury come on should involve:
• Gentle stretching
• Gentle stretching
• 10-15 minutes ice massage (i.e. Frozen dixie cup), 2-3x/day
• Topical anti-inflammatory (Traumeel is one of my favorites)
• Topical magnesium (10-15 sprays rubbed in over area)
• Substitution of elliptical trainer for runs

• Deeper stretching and preferably yoga
• Return to running, but with a bicycling or brisk walk warm-up to heat the muscle (you can even try a topical heating ointment, like Greyhound)
• Dynamic leg swings front-to-back and side-to-side both before and after workout
• Warming up VERY well before your runs
If it continues to give you trouble, you may need more aggressive therapy, like Active Release Therapy, Primal Reflex Release Technique, Chiropractic, Acupuncture or Deep Tissue Massage. (Reposted with permission from my friends at TrainingPeaks blog.)
Ben hosts the highly popular fitness, nutrition and wellness website at http://www.bengreenfieldfitness.com/, which features blogs, podcasts, and product reviews from Ben. In addition to coaching and training for weight loss and sports performance at http://www.pacificfit.net,/, Ben serves as a business and marketing consultant to fitness professionals, and is the host of a weekly syndicated fitness business blog and podcast at http://www.trainfortopdollar.com/.