I'm wanting to go from a 21:10 minute 5k to 19-20 minutes in 3-4 months. I currently run 10-15 miles a week and working on building a base up to 25-30 miles a week with one tempo run ,one long run, and two easy 3 mile runs. Will this be enough to improve my time to under 20 minutes? I am also just 2 months back to running after Posterior Tibial Tendonitis. Before the injury I was running 12 miles a week and ran the 21:10 5k on that mileage with just 3 months of training and not running for 8 years.