Concentric-only training has exploded over the last two years or so and with the publication of this study last week, I’m sure that this training modality will continue its rapid surge in popularity. So, what is this ‘concentric-only’ training and why should you care? Here’s what you need to know.
How Do Muscles Work?
Generally a repetition consists of two distinct phases. We’ll use the classic bicep curl exercise as our example here:
- The Eccentric Phase
This is the lowering or negative portion of the repetition. In our example this would be moving the weight from the shoulder down towards the thigh. Here, the biceps group lengthens under tension.
- The Concentric Phase
This is the shortening or positive portion of the repletion. Our example would see the raising of the weight from the thigh towards the shoulder. The biceps group shortens under tension.
Muscles are far stronger eccentrically than they are concentrically. Greater forces are produced during the eccentric portion of a repetition and greater mechanical stress is accumulated. Generally this would be considered a good thing as it carries greater potential to improve strength and initiate hypertrophy. However, it is these ‘strengths’ of eccentric muscle action that are also its drawbacks. It’s the eccentric phase of an exercise that causes the most damage and carries the greatest potential for soreness. It’s much more demanding on the body and the central nervous system, and therefore takes longer to recover from.
Eccentric vs Concentric
Although the limiting the eccentric phase may reduce the potential for training adaptation, it does not remove it entirely. Indeed, this meta-analysis from Roig et al suggests that whilst eccentric training may be preferred for improving both total and eccentric strength to a greater extent than concentric training, improvements in concentric strength appear comparable between the two modalities. This is important because although eccentric strength is crucial in sport, it’s typically an athlete’s ability to produce force concentrically that has a greater bearing on overall performance outcomes.
What Does The New Study Say?
West et al concluded that a reverse sled pull training session (a concentric-only exercise) may provide an effective training stimulus whilst causing minimal stress to recovery mechanisms. Athletes in the study performed 5 sets of 2 x 20m sled pulls with a sled loaded with 75% of their body mass. The session induced significant elevations in testosterone, cortisol and lactate, indicative of a strong metabolic and hormonal stimulus. Despite creating this stimulus the training session did not induce significant muscle damage (determined creatine kinase levels) and only acutely impaired neuromuscular function. Specifically, jump performance was reduced at 1 hour post-session but was recovered at 3 hours post-session. ‘Traditional’ resistance training sessions may be expected to impair neuromuscular function for around 2 days.
So, in theory, if we could remove the eccentric part of an exercise we should still be able to elicit a training effect but also reduce potential muscle soreness and recovery time. Welcome to the concept of concentric-only training. This can also be termed as concentric-biased or eccentric-less training (as you can never completely eliminate eccentric muscle action). We utilise specific exercise variations or forms of resistance to minimise the phase. Examples could be a deadlift where an athlete drops the bar at the top of the lift or pushing along a weighted sled.
Potential Application of Concentric-Only Training
We can use concentric-only training in two ways depending on the situation an athlete is in
- As a ‘Deloading’ Strategy
To maintain a training stimulus but with a reduction in stress on the body
- As a ‘Loading’ Strategy
To increase the overall volume of training without creating excessive stress on the body
Regardless of how and why it may be employed, it is important to note that concentric-only training should be seen as supplementary to ‘traditional’ resistance exercise.
Hopefully this article has given you a quick primer on concentric-only training and has got you thinking about situations where it may be appropriate for you to utilise it. The next article in this series will look at the application of concentric-only training and give some ideas of how to incorporate it into your programmes.