The repeated bout effect describes how your body becomes better at handling a specific type of stress it has already experienced (Nosaka and Clarkson 1995).
When you do a hard or unfamiliar workout, like a long downhill run, your muscles experience microscopic damage and inflammation. The next time you do something similar, your body remembers that stress and adapts through structural, neural, and connective tissue changes, so you do not get as sore or fatigued (Hyldahl, Chen and Nosaka 2017). For downhill workouts in particular, this adaptation can last for several weeks, which is why you only need to do faster downhill sessions about every two weeks or even less often, depending on your race needs. The benefits tend to last longer than those from most other types of training stress (Chen, Nosaka and Tu 2021).
Downhill running places a high eccentric load on your muscles, especially the quadriceps, which control your descent and stabilize your knees under increased impact forces (Eston, Mickleborough and Baltzopoulos 2019). Instead of pushing you forward, they act like brakes to maintain control and prevent knee collapse. This braking role becomes even more important on steep or extended descents, where both pace and impact forces are higher.
Doing strength work that includes eccentric exercises may help your muscles absorb force more effectively and reduce muscle damage in future sessions (Douglas, Pearson, Ross, and McGuigan 2017). For road or trail runners who struggle to get in as much climbing and descending as their races demand, eccentric strength training and some targeted downhill running can help ensure their legs hold up in the later stages of a race.
A Simple Strength Routine
Try including these exercises when you want to prepare your legs to resist fatigue at the end of a race:
- Step-downs from a low box or step, lowering slowly for three to four seconds, 8-10 reps per leg
- Slow Bulgarian split squats, lowering for three seconds, 8-10 reps per leg
- Single-leg Romanian deadlifts, focusing on control during the lowering phase, 8-10 reps per leg
- Optional wall sits or slow walking lunges for extra quad endurance
If this is your first time doing eccentric strength work, start easy. The goal is to feel the muscles working, not to push to failure. Move slowly and with control, keeping effort around five to six out of ten, and stop well before you feel fatigue. Even one set per exercise is enough for the first week. Mild soreness is normal, but if it lasts more than a couple of days, reduce the load next time. If you are already used to lifting, you can work at a higher load with fewer reps, like four to six, while keeping the focus on slow, controlled lowering.
Focus on Form
Good form is everything. Poor form reinforces bad movement patterns and increases injury risk. Control the movement through the full range, keep your knees tracking over your toes, and maintain a neutral spine. If you feel pain in your knees or lower back, adjust your form or reduce the load. Find tips for good form here.
Downhill Running
Downhill running is an excellent way to condition your legs for descents and build the resilience needed to stay strong late in a race. However, because downhill running increases impact and muscle stress, it is best reserved for runners who are healthy and injury-free.
Aim to include a faster downhill session about every two to two and a half weeks during the final six weeks before your race, with the last one roughly two weeks before race day. Depending on your race profile and how much eccentric strength work you are doing, one or two downhill sessions may be plenty. For some runners, simply doing a lot of vertical gain and including a few moderately fast downhills may be enough. Here are some examples of what that could look like.
For road marathoners without access to big hills: You can simulate downhill stress by running a short, controlled downhill segment at near top speed. For example, run a 1-minute downhill effort five to eight times at the end of a long run. Focus on good form and maintaining control rather than pure speed.
For ultra runners tackling a mountain hundred: Include a runnable but somewhat steep downhill in a long run, aiming to descend two thousand or more feet if your terrain allows. Run at a fast but controlled pace that challenges your quads and downhill mechanics without risking form breakdown or injury. Adjust distance and intensity based on what your race course will demand and how fatigued you are from the rest of the run.
Bringing It All Together
Downhill running and eccentric strength work are just one small part of your training picture. Consistency, building volume, training specificity, and hitting the right workouts at the right time are what really make the difference. Combining controlled downhill running with eccentric strength training helps your muscles adapt and become more resilient, allowing you to handle descents, long road stretches, or the final miles of an ultra with less fatigue and soreness.
Plan your final hard downhill or eccentric strength session about two weeks before race day so your legs have time to recover and adapt. You will show up strong, fresh, and ready to roll.
References
Chen, T. C., Nosaka, K., and Tu, J. H. 2021. Changes in muscle damage markers and repeated bout effect after different eccentric exercise protocols. Frontiers in Physiology, 12, 654
Douglas, J., Pearson, S., Ross, A., and McGuigan, M. 2017. Eccentric exercise: Physiological characteristics and acute responses. Sports Medicine, 47(4), 663–675
Eston, R. G., Mickleborough, J., and Baltzopoulos, V. 2019. Eccentric exercise-induced muscle damage and adaptation. Strength and Conditioning Journal, 41(2), 31–39
Hyldahl, R. D., Chen, T. C., and Nosaka, K. 2017. Mechanisms and mediators of the repeated bout effect. Exercise and Sport Sciences Reviews, 45(1), 24–33
Nosaka, K., and Clarkson, P. M. 1995. Muscle damage following repeated bouts of high force eccentric exercise. Medicine and Science in Sports and Exercise, 27(9), 1263–1269