Here we’ll discuss the significance of eccentric contractions during downhill running and its contribution to DOMS (delayed onset muscle soreness). We will also look at the effectiveness of eccentric training as part of a strength or rehabilitation training program.
Most of you will be familiar with the paradoxical muscle soreness resulted from running downhill felt a few days following a training session. During a descent, the body’s running biomechanics significantly changes to facilitate a new landing pattern which acts to counteract downhill acceleration. In doing so, the quadriceps muscles in particular undergo a greater degree of eccentric muscle contraction which aids in neutralising the accelerative force component.
What is an eccentric contraction?
Although ‘contraction’ would suggest something shortening, in muscle physiology it describes the production of tension. Tension in a muscle can be produced under 3 scenarios:
- Muscle shortening = concentric muscle contraction
- Muscle lengthening = eccentric muscle contraction
- Muscle remaining same length = isotonic muscle contraction (e.g. during a planking exercise)
Concentric contractions are fairly straight forward: a collection of a muscle’s fibers shorten due to their protein sub-units pulling, or better put, ‘sliding’ one another closer together, and the shortening creates enough tensions to overcome the load that’s being lifted. Eccentric contractions are, however, slightly different.
An eccentric contraction doesn’t cause a muscle to lengthen, but rather provides a resisting force to decelerate the lengthening movement, providing an important breaking force. By opposing the downward force, a joint is safely repositioned and tissue is protected. This occurs through some muscle fibers remaining active throughout the stretch, to maintain tension within the muscle.
It is worth mentioning that concentric and eccentric contractions are coupled together by opposing muscle groups. For instance, in the above figure, an eccentrically contracting biceps (brachii) muscle is coupled with a concentric contracting triceps (brachii).
Eccentric leads to greater breakdown
As mentioned earlier, fewer muscle fibres are recruited to actively work in generating muscle tension during eccentric than during concentric contractions. A notable reason for this is to minimise energy expenditure on what is simply a resistance force, as fewer working fibres means less consumed energy. Aside from this, our muscles can also resist approx. 1.75x more force than what they can overcome. As such, even under regular loads our muscles experiences greater tension per muscle fibre during eccentric contractions and are therefore more vulnerable to muscle damage.
The figure above illustrates how reliant our gait becomes on our quadriceps eccentrically contracting, and I’m sure this gives you an idea of the tension muscle fibres are under while descending.
Muscle breakdown and DOMS
A working muscle producing tension will naturally experience tissue breakdown, specifically of its contractile proteins. Breakdown can be described as micro-tears of the muscle. Our body’s repair response in amending damaged cells stimulates various receptors that trigger our DOMS sensation. However, the more we become accustomed to a training stress, the more resilient our muscles become to tissue breakdown in future. Furthermore, our pain receptors become desensitised to the repair stimulus that makes us feel sore (well-trained athletes can be in a state of fatigue without feeling sore), while also becoming more efficient in recovery.
Eccentric training provokes a variety of muscular and neural adaptations that have beneficial effects for sports performance and injury rehabilitation. Such exercises involve either isolating or emphasising the eccentric contraction within the movement. Examples of exercises can be found at the bottom of this page.
Benefits of eccentric training include:
- Increased concentric muscle strength
- Strengthening of connective tissue – which helps reduce the risk of injuries
- Improved flexibility (some studies have found this to be more effective than static stretching). Figure 3 demonstrates how lengthening a hamstring under tension can simultaneously work train muscle flexibility.
Consider using this modality of training periodically, or mixed within a balanced training program (1-2x/week), as it tends to give rise to greater muscular stress than what an athlete’s perceived exertion would suggest. This is partly due to the relatively low O2 consumption and energy usage in comparison to concentric contractions. Athletes incorporating this periodic use should avoid practicing this in season to prevent unwanted central fatigue and tissue breakdown. During this time you also do not want to upset your ability to recover.
When performing eccentric exercises, emphasise the lowering portion of a lift, and perform slowly (+/- 5sec). A good unit of measurement to quantify your work is the amount of time your muscles are under tension (‘time under tension’). Keep in mind that performing slow movements will not make your muscles become slow. It should also be noted that the volume and intensity of eccentric training, like everything, comes down to the goal of training: achilles tendinopathy recovery might make use of body weight eccentric heel drops, while a rugby player’s bench press strength might make use of 140% 1RM (rep max) for one quarter of the volume.
Example of eccentric exercises: