Too cold and icy and to run outside? Try adding in some strength training! A 2017 systemic review has shown that adding strength training to a distance runner's program in the form of heavy resistance training, explosive resistance training, and plyometric training performed on 2–3 occasions per week is likely to positively affect performance in terms of: Running economy, time trial performance, and maximal sprint speed in middle- and long-distance runners of all abilities.
Adding in strength did not affect: maximal oxygen uptake, blood lactate parameters, or body composition. Add in the some resistance and plyometric training now and see the benefits come running season in the spring!