Should I be lifting in the gym?

Yes. Runners should include a multi-joint strength training program in their weekly routine. Two times per week for thirty minutes a session is sufficient to address core and lower body strength in runners. Strength training for runners has a dual focus, it aids in both run speed and injury prevention. Multi-joint movements are optimal when they closely mimic the motion and demands of running. Strength training sessions should be separated by at least one day in the week to allow for adequate recovery between sessions. Strength training days should also not fall on extremely difficult run workout days to avoid chances for injury. On hard run workouts, the body is fatigued and a fatigued body can lead to improper form while performing the strength training exercises. Improper form can increase the incidence of injury. The primary rationale for strength training in runners is that a stronger muscle is a more efficient muscle. So a short strength training session can help an athlete even in endurance events, up to a certain point, however. If strength gains lead to excessive weight gain, then strength training can be counter productive for runners. The optimal strength training program includes lighter weight with more repetitions to promote efficiency as opposed to hypertrophy (building muscle mass). Two to three sets with ten to fifteen repetitions is optimal for runners.