Why is this? Let me quote Matt Fitzgerald, author of "Runner's World: Cross-Training for Runners" in his latest book "Racing Weight":
"Endurance athletes are generally taught that they should use moderate loads and perform sets with large numbers of repetitions (12-rep sets are typical), because this approach imposes a strength-endurance challenge that is more relevant to endurance sports performance than the strength-power challenge imposed by lifting heavier loads. However, the point of hitting the gym if you're an endurance athlete is not do the same type of training you do in your primary sports discipline(s). The point is to get a type of training stimulus that you are not getting from your endurance training. Lifting very heavy loads is exactly the sort of thing that endurance athletes should do in the gym, because it complements rather than reifies their endurance training."
Seemingly a simple point: "Don't do training that is similar to your endurance training because its adding insult to injury". My physiotherapist John Murphy has made this point on the usage of high-repetition calf-raises to me in the past: "Don't do it while you're doing high mileage as running is basically calf raises." It's a bit simplified calling running calf raises, but the point is well made: If you run 100 miles a week and do lots of calf raises you are simply adding more of the same.
Before we go back to the best strength training methodology for endurance athletes let's look at the WIIFMs (What's In It For Me!) of doing it in the first place:
- Greater maximal strength output
- More optimal body composition
- Greater injury resistance
The second benefit deserves particular comment: One of the limiting factors of how many calories we can burn is the amount of time we can spend exercising within our sport. Running is the worst of the endurance sports in this respect because the least amount of actual hours "on our feet" (as opposed to "on the bike", "in the water", "on the skis") can be tolerated.
Adding a type of exercise that is different, yet beneficial to running (some types of exercises are detrimental as we shall see), will lead you to burn more overall carbs and increase your percent of muscle-mass overall which again increases your metabolism. This is before counting the strength gains.
So if you want to prepare yourself for the life of a professional athlete which can entail 10-30 hours of weekly training, run as many hours as you can and fill out as much extra time with non-detrimental cross-training, strength training among it.
Arthur Lydiard himself was no fan of strength training mainly because of the risk of bulking up his athletes and instead swore to the use of his famous hill training phase (featuring short powerful uphill drills). The advantage of these drills is that they are more running specific than weights and provide some cardiovascular stimulus; the disadvantage that you still only carry the load of your body (not heavier) and that it adds running miles to your legs (only a disadvantage if you're at the brink of what you can take).
Both Matt Fitzgerald and the authors of "Advanced Marathoning", Pete Pfitzinger and Scott Douglas, support use of similar hill exercises:
"I recommend runners perform one set of 6-10 x 8-10 second sprints up a steep hill each week" (Fitzgerald 2009, 180)"
"If lifting weights isn't for you, then try another form of resistance training - hill training. During hill running, your body weight is resistance. There is some evidence that running hills can produce improvements in running economy similar to those that occur through "normal" resistance training." (Pfitzinger and Douglas 2009, 95).
A similar approch can be found in "Better Training for Distance Runners" by Peter Coe (father of Seb) and David Martin. Suffice it to say: It works, and it is a ubiquitous practice among successful runners. Arthur Lydiard dedicated a specialised 3-6 week "hill phase" to heavy usage of this training (3 sessions a week, as well as a sprint session) but using Matt's suggestions of one hill sprints/hill drill session per week may be a more practical way for most to implement his dictums.
Voice of the Lydiard Foundation
In "Healthy Intelligent Training", a book endorsed by the Lydiard Foundation, Keith Livingstone dedicates a chapter to strength training and his conclusions are identical to Matt Fitzgeralds on using weights:
"I know from my own experience that mixing an endurance-based running program with conventional weight training can be counter-productive for endurance but there is a way to do it properly that we can still explore. Heavy lifting at near-maximal is thought to recruit the fast twitch fibres very early in the lifting phase and bypass the slow twitch fibers...Very heavy lifting (above 85% of your 1 rep maximum) with few repetitions, in a few sets, with plenty of recovery between sets, will primarily recruit and train the fast twitch fibres and their huge incoming neural pathways." (Livingstone 2009, 174-175)
Keith Livingstone goes on to warn about the risk of increased muscle volume and localised glycolytic acidosis caused by moderate load multiple-rep weight training: Well known to be detrimental to both muscles and your nervous system or as he puts it in short: "Alactic lifting for the IIb fibres (red: fast-twitch muscle fibres) will increase strength and speed potential without increasing useless mass" (Ibid, 178).
What type of Exercises to use?
To effectively transfer the strength gained from heavy lifting into endurance sports, you need to develop power, as well, to enable the transfer of the force gained from strength training into movement. The hill sprints suggested by Matt Fitzgerald or any uphill or sprint drills (such as Lydiard's) serve exactly this purpose and therefore go in tandem with your strength training. Plyometrics is another such training modality but too broad a topic to cover here.
Livingstone suggests the Deadlift as being the best of all exercises to do with heavy-loads because it works all major leg muscles, several upper body muscles and is an easier exercise to perform than the squat. A more general recommendation is to use compound exercises that mimic natural movements such as step-ups, dips, and push-ups rather than static weights. Arthur Lydiard famously recommended you got a pile of gravel dumped and then started shovelling it into another pile). The books by Fitzgerald, Pfitzinger & Douglas, Noakes, and Coe and Martin all offer good samples of such exercises but any strength-training book will get you started if you know what to look for.
Matt Fitzgerald provides another basic principle for endurance athletes to employ: "There is no need to pad your workout with multiple exercises for the same muscle group or numerous sets of each exercise. Just get in, go hard, and get out." (Fitzgerald 2009, 179)
So, in conclusion, when you are training hard, do not perform weight training that mimics your running (limit this to periods when you don't, or can't, run) but instead exercise with very heavy loads and low repetitions (about 10 seconds active maximum or 4-5 reps). Prefer simple compound exercises that mimic natural movements over static isolation exercises.
Almost all sources agree that 2-3 sessions a week is plenty for endurance athletes and duration need not be more than 20 to 40 minutes (Ibid., 179). Core workouts and flexibility training are not included in this and are a separate topic and a form of training that should be done in addition to strength training (but can be done quite effectively in conjunction with it). Its recommended to do any exercises after running sessions, not before, to optimise performance in your running workouts (which remain your bread-and-butter).
Finally, you should combine this training with at least one weekly uphill sprint session (short 8-10 sec sprints) or hill drills like those devised by Lydiard to provide a functional outlet for your newfound strength. Flat sprints work as well and are very useful but provide less resistance while still stimulating your fast twitch fibres.
Red: As Tim points out below you can add resistance to flat sprints by using weighted vests or parachutes. There are other ways, such as dragging a partner behind you (he can grip you with his hands or with an elastic band). The advantage of running on the flat is that higher speeds can be achieved on the flat if you want to generate more neuromuscular stimulation for leg-turnover. However, if your focus is strength, hills are still very useful for road and track runners. Lydiard never trained a hill runner, yet swore to the use of the hills for his champions in the 800m, the 5000m and marathon (Snell, Halberg and Magee). It goes without saying that this form of exercise is extremely race-specific for steeplechasers and cross-country runners.