Muscle contractions in sports are usually isotonic, involving changes in length of muscle fibres, that can be classified in concentric and eccentric contractions.
Concentric muscle contractions
Muscle generates tension, to overcome a resistance. There is a shortening of the muscle fibres and a movement of a body part. An example could be any exercise with weights or running uphill.
Eccentric muscle contractions
Opposite than in the concentric contraction, in the eccentric there is a lengthening of the muscle fibres against a resistance. The force applied to the muscle exceeds the force produced by the muscle itself.
Another type of contraction, without changes in the length of the muscle fibres, would be the isometric contraction.
Downhill running (DR)
Downhill running involves repetitive eccentric muscle contractions, which cause mechanical strain on the musculotendinous system of the lower limbs and exercise-induced muscle damage, or EIMD, whose physiological alterations last for several days after the exercise.
In many off-road races taking part in natural environments the sections involving DR are very common. Among these races we could talk of trail running, mountain running or the more specific fell running modality, although many road races also include important downhill sections.
Scientific evidence suggests that previous exposure to DR is the most effective strategy to help reduce the extent of EIMD among runners. Thus, it helps improve resultant effects of EIMD: force losses, changes in running economy and mechanics, structural alterations, and inflammation levels.
The effect of this pre-exposure is known as “Repeated Bout Effect”, or RBE, and there are studies showing that it can be achieved performing only a couple of bouts of DR separated by several days.
The mechanisms associated with this effect would include:
- Neural adaptations
- Adaptations of the muscle-tendon complexes
- Increased sensitivity to inflammation
- Improved muscle remodelling
The RBE could be summarized as simply as:
Other alternative strategies such the use of lower limb compression garments or specific running shoes have shown potential in the adaptation to DR, although more studies are needed.
If you have races involving DR your best strategy should include a few sessions of training in similar conditions to those you will find on race day!
Downhill Running: What Are the Effects and How Can We Adapt? A Narrative Review.
Bontemps B, Vercruyssen F, Gruet M, Louis J. Sports Med. 2020;50(12):2083-2110. doi:10.1007/s40279-020-01355-z