Running injuries are the result from cumulative, repetitive stress on the body. They aren’t the result of one-off hard efforts. By running key workouts just 1–2 times per week, you capture the benefits that come with hard training, while keeping your risk of injury low.
If you stress your body appropriately through hard training, then give it time to recover, you’ll get faster.
Too many runners focus just on the hard training and ignore recovery. They make the mistake of not allowing for adequate recovery between workouts.
You’ll only get faster if you allow your body to properly recover between workouts.