Not at all! By taking a cross-training-based approach to training, you can run a lifetime-best marathon on just three or four runs a week. Incorporating non-impact cardio workouts and functional strength workouts into your program will reduce your chances of getting injured not only by limiting your running mileage, but also by increasing the stability of your joints (as joint instability is the primary cause of most running injuries).
Your cross-training workouts will also enhance your running performance, more than making up for the running miles that are cut from your program to make room for cross-training.
In my book Runner's World Guide to Cross-Training, I outline a 24-week plan that provides an example of how to cross-train your way to a personal best marathon. It's appropriate for runners who are currently able to run three or four times a week, up to one hour per run. In addition to three weekly runs, the schedule includes an optional fourth run, an alternative cardio workout and two strength workouts a week.
Such a minimalist approach to training requires that you make each run really count. Therefore, most of the three weekly scheduled run workouts are rather challenging, with high-intensity work on Tuesdays and Thursdays and a long run on Sundays. Here's a key to the workout types:
- Foundation run - A steady run at a comfortable, moderate aerobic pace
- Strides - 20-second relaxed sprints with 40-second jogging recoveries
- Long run - A long run done at the same pace as your foundation runs
- Hill repetitions - Uphill running intervals done at near maximum intensity with two-minute jogging recoveries
- Fartlek run - Foundation run with scattered 30-second bursts at one-mile race pace (i.e. the fastest pace you could sustain for five to seven minutes)
- Tempo run - Steady run at a threshold pace (i.e. between 10K and half-marathon race pace) sandwiched between a long warm-up and cool-down
- Speed intervals - One-minute running intervals done at speed pace (one-mile race pace) with three-minute active recoveries
- Lactate intervals -- One- to three-minute running intervals done at VO2max pace (i.e. 5K race pace) with jogging recoveries of equal duration
The alternative cardio workouts are foundation-intensity workouts in your choice of the following activities: pool running, elliptical training, bicycling (indoors or outdoors) or inline skating.
Your strength workouts should incorporate strength-building movements with functional carryover to running, such as forward lunges, as well as core strengthening movements and jumping drills to build stride power. Do a total of nine to 12 different movements in each strength workout. For detailed strength-training guidelines for runners, check out my book, Runner's World Guide to Cross-Training.
Every fourth week of the plan is a recovery week, with reduced training to allow your body absorb and adapt to your recent hard training and prepare for even more challenging workouts in the coming weeks. A 5K tune-up race is scheduled for the end of Week 12, a 10K tune-up race at the end of Week 16, and a half-marathon tune-up race at the end of Week 16. If you can't find formal races to do on those days, run time trials instead.