Downhill Running: How to go faster and hurt less

What goes up must come down. In the case of ultrarunning, coming down can be the more painful of the two. Running downhill leads to a lot of muscular damage (more on that later) and wrecked legs. As a result, some coaches spend a lot of time specifically focused on preparing an athlete’s legs for the abuse they’ll take during races with a lot of elevation gain/loss. It’s an understandable motive, but ultimately I think it requires less time and less effort than most people realize.

Why you get lead legs

Lead legs are caused by two primary factors-

• Excessive damage to the musculature, primary caused by many, heavy eccentric contractions
• Neuromuscular fatigue

While there is neat research emerging on the sources and means of combating neuromuscular fatigue, most ultramarathon training has focused on stifling the muscular damage caused by downhill running.

As your run downhill, your quads simultaneously activate and lengthen to absorb the shock of running downhill and gradually lowering your center of mass. This active lengthening of muscle fibers is oxymoronically termed an ‘eccentric contraction’. Maybe eccentric activation would be a better term. It is the primary (but not exclusive) culprit for muscular damage. Eventually, the damage leads to leaden legs many ultraunners experience later in races.

What we know about damage caused from eccentric work 

Simply put, it’s a lot of damage and it’s highly variable. Researchers can use a few techniques to peer into the physiology of muscular damage. They can literally take a look at the muscle fibers by either taking a (small) chunk of muscle out to inspect under a microscope, or use an MRI to look at the soft tissue. In addition to actually looking at the muscles themselves, blood biomarkers – primarily Creatine Kinase (CK) – can be used as a proxy for muscular damage.

The former imaging techniques have their strengths. However, much of the research done on muscular damage uses blood biomarkers. This is simply because the tests are easier, more cost effective and accessible. Creatine Kinase, for instance, increases in the blood due to muscular damage (among other things). This means higher levels of CK theoretically mean higher levels of muscular damage.

The figure below represents CK levels from 22 individuals after participating in the Ultra Trail Du Mont Blanc. For a reference point, a CK level of <198 U/L is considered normal. After a marathon, these levels might rise to 2000-4000 U/L (Siegel 1980). As can be seen in the chart below, a 100-mile ultramarathon can result in CK levels from 10,000 to 50,000 and even higher. That’s a ton of damage to contend with in an ultramarathon.

(Millet 2011)

What we can also see from this chart (as well as similar research) is tremendous variability among individual athletes. It is theorized that a combination of training, technique, and perhaps genetics account for the individual variation.

Overload is either volume or intensity or both

To combat muscular damage, ultrarunners utilize a variety of techniques. First, they can simply run up and down hill over varied terrain. Second, they utilize strength training exercises like squats. Finally, ultrarunners have taken to running downhill very hard in order to ‘season’ the quads. I’ve never really understood as it conjures images of Julia Childs rather than Tony Krupicka. In any case, the strategy, like any other training strategy, is to overload the musculature with either volume (run up and downhills) or intensity (strength training and hard downhill running), or both.

The repeated bout effect

Eccentric work done by the muscles is quite interesting. During an active lengthening of the muscle, an athlete can do more work with less cardiovascular effort. So much so that cycling in reverse (primary eccentric exercise) has been used in cardiac rehabilitation protocols, which gives the patient a workout but has less cardiovascular load. The consequence of this type of muscular activation is that it causes a lot of damage.

For decades, researchers have used eccentric contractions in order to induce muscular damage and thus study effects on supplementation, interventions, the time course for muscle repair, and other phenomena associated with breaking down and building back muscle fibers. Along the course of this research, they have found that there is a strong protective effect associated with eccentric training. The effect is so strong that one bout of eccentric training can have a protective effect of subsequent bouts performed weeks later. The aptly term coined for this effect is the ‘repeated effect’. This means a single bout is enough to provide a lasting protective effect.

Dose response to training

As coaches, we are always looking for the right dose response to the training we prescribe. For example, we know a trained runner needs greater than 10 min of work at above 90% of their VO₂ max in order to produce a meaningful adaptation to their VO₂ max. In this case, the dose is the time at intensity (>10 min at > 90% of VO₂ max) and the response is an increased VO₂ max. Knowing the correct dose response results in workouts that look like 6X3 minutes hard, 3 minutes easy (18 min of total work) in order to improve VO₂ max. Conversely, a workout like 10X1 minutes hard, 1 minute easy is unlikely to have enough load (time) to produce a meaningful response. Get the dose right and the response will follow.

When we think about how to adapt an ultrarunner to the eccentric loading required in an ultramarathon, the inoculation effect can provide some clues into what the right dose is to get an adequate response. While the protocols are not as precise as the VO₂ max example above, the theme that can be taken away is that a small dose (of eccentric work) goes a long way (inoculation).

The right way to prepare for the downhills

Because of the strong dose response relationship with eccentric work (relatively low doses lead to large responses) I feel it is unnecessary to contrive workouts to be prepared in this area. If you have terrain hilly enough to match (or approximate) your race’s elevation gain/loss per mile, run on that terrain. Your everyday Endurance Runs are likely a big enough dose to condition your legs for the downhills.

There is likely a skill aspect to effective downhill running. The more skillfully you can run downhill, the less wear and tear on your legs. As a result, I think that running more technical terrain at a normal Endurance Run intensity from time to time is a good thing. I would rather have runners improve their trail skill with a more technical terrain run at a normal intensity vs benign terrain run faster (you can see this article for how we improve downhill skills at our camps).

Costs of hard downhill running

While I don’t advise hard, fast downhill running, if you feel the need to do so, it is important to understand that such work will come at a cost. Namely…

• Increased recovery time due to the effort. You will need at least 2-3 days of easy running after a hard downhill effort. So, before you plan a hard downhill session, make sure doing so doesn’t compromise your overall training volume.
• Increased risk of injury, either due to the excessive pounding or acute injury from a fall

I theoretically could see the utility for hard downhill runs if terrain is limited. However, even in those cases, it’s a tough risk-reward to balance. On the plus side though, all an ultrarunner should need is 1-2 sessions to create an adaptation (inoculation effect in force here again).

In a previous article, I reviewed the need (or lack thereof) for strength training. So I am not going to rehash those arguments here. If you choose to strength train, I’m not convinced being better prepared for downhills will be an outcome. So, you better do it for other reasons.

By Jason Koop,
Head Coach of CTS Ultrarunning

References

1. Millet, Guillaume Y., Katja Tomazin, Samuel Verges, Christopher Vincent, Régis Bonnefoy, Renée-Claude Boisson, Laurent Gergelé, Léonard Féasson, and Vincent Martin. 2011. “Neuromuscular Consequences of an Extreme Mountain Ultra-marathon.” PLOS ONE 6 (2): E17059.
2. Siegel, A J et al. “Creatine kinase elevations in marathon runners: relationship to training and competition.” The Yale journal of biology and medicine 53,4 (1980): 275-9.