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Keith Baar: Tendon Health and Performance

In this video Dr Keith Baar, a molecular biologist from the University of California, who has a practical background in strength and conditioning talks about the relationship tendon health and performance.

Tendon Performance V’s Tendon health follow-up

The video presentation by Dr Keith Baar, on the topic of manipulating tendon stiffness, generated quite a lot of discussion, and a number of questions were forwarded to us here at uCoach. These questions were relayed to Keith and he has kindly sent on his replies, you can view a sample of these questions and answers at the bottom of this blog. A special word of thanks to Martyn Jones and Graeme Woodward for taking the time to raise these issues.

In relation to the questions sampled below, be aware that the next video presentation in the series focused on optimising athletic movement efficiency is due to be released over the coming days. This presentation (by the coach and biomechanics researcher Dr Drew Harrison) will address, and add clarity to, some of the issues discussed below. So if some of these issues do remain clouded, then hopefully we will clarify them as we progress through the series.

In the meantime, please do keep your comments and questions coming.

Q: Martyn Jones

It is my understanding that a more compliant tendon is not only better for muscle injury prevention but also for performance during stretch-shortening cycle movements eg running (ref’s Kubo et al 2005, Lichtwark et al 2010). Therefore, I do not see the conflict between tendon health and performance you mention. Research suggests that a stiffer tendon may well be better for purely concentric muscle contractions. Ballistic stretching has been shown to increase tendon compliance, but static stretching seems to have little effect. So, ballistic stretching could be used instead of, or with, slow eccentric contractions. Keith does not mention stretching. I am uncertain if Keith’s recommendations are based upon research I have not seen or on unpublished work. Your clarification would be most welcome

A: Keith Baar

What happens to tendon compliance during certain training interventions is controversial. What is clear is that increasing stiffness increases energy return and therefore performance. This is the reason that Oscar Pistorius was said to have a performance advantage. The stiffness of his cheetahs allows him to get more energy back from each step than someone with biological legs. The result is improved running economy (i.e. it costs him less metabolic energy to perform the same movement than it does an able bodied runner).

As far as stretching. This is very difficult to really understand what is happening. More often than not, people find what they set out to find since there is not a reliable test for stiffness of tendon in humans. Having said that, static stretching just prior to exercise is supposed to decrease tendon stiffness (Kubo et al JAP 2001; Morse et al J. Physiol 586(1): 97 - 106) and as a result decrease performance in sprint exercises (for example Fletcher and Jones Journal of Strength & Conditioning Research 2004). Ballistic stretching right before competition (according to Fletcher and Jones and some others) is supposed to improve sprint performance and this suggests that it would increase muscle-tendon unit stiffness. A lot more needs to be done on this issue if we are going to really understand what is happening.

Q: Graeme Woodward

What is the range of loading parameters for loaded eccentric muscle action to promote 'tendon health' ( as increasing load towards 1RM will promote activation ) as defined by the presenter, and when does this become strength training rather than a 'slow, ( loaded ) eccentric stretch'? Are there speed and time parameters within this, to differentiate from an eccentric dynamic stretch?

A: Keith Baar

The eccentric loading of tendon to improve health is essentially strength training using a weight that is greater than 1RM. The biggest difference is that the speed of movement should be less than the lengthening phase of a normal repetition. Here, the lengthening phase should last >8 seconds for the full range of motion.

Q: Graeme Woodward

How do speed definitions fit into plyometric classification and when does this affect MTU use as a whole?

A: Keith Baar

Plyometric training by definition uses high speed movements. This ranges everywhere from sprint training to quick jumps, to hops etc where you are trying to minimize contact time with the ground. This type of exercise will initially result in a large increase in stiffness (related to injury in a novice) but after recovery from that phase you see a progressive increase in stiffness over time.

Q: Graeme Woodward

Most of the early discussion referred to tendon input on the flat because, I presume, of the T&F context, at what gradients does he define flat becoming uphill in terms of his statements about increasing emphasis on muscles in uphill running. And won't this depend on the degree of eccentric action of a dorsiflexed foot and ground contact time?

A: Keith Baar

Since the role of muscle is to overcome inertia, as soon as any gradient is introduced the muscle starts to do more work since inertia (i.e. the gravitational force) would become greater. This is most related to the force that you are trying to overcome. As a result, the force that you are working against is dictated by mass X acceleration, where the mass can be estimated by the weight of the person and acceleration is determined by gravity. On a flat, the acceleration due to gravity is perpendicular to the movement. As soon as an incline is introduced, the athlete is working against greater force (acceleration equivalent to the cosine of gravity) and this increases the resistive forces resulting in a greater need for muscle contraction.

Q: Graeme Woodward

Keith differentiates between health and performance as a risk continuum, has he revealed any indicators which flag up entering a risk zone?

A: Keith Baar

Nothing specific has been determined by scientists. I would think that this is something that talking with other coaches may be more beneficial.

  • Uploaded: 18.05.2010
  • Duration: 00:40:24
  • Views: 2970


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Comments (1)

  1. Posted by Neil Tunstall on 12/08/2010 at 01:06 PM

    Second half the best.  Talks about adapting weights programmes and some nutrition work.  One question I have is how long before endurance training should you consume carbohydrate to still benefit from the low glycogen effect?  Traditionally, my squad tend to have a light snack at about 4pm if training at 6.30pm and then protein and carbs within 15 mins of training coming to an end.  We do not have energy drinks during sessions.  Does this meet the criteria for low glycogen training?  Before a race I tend to eat at least 3 hours before, but supplement this with a sports drink leading up to race.  How does racing differ to training?

    First half, fairly obvious and well known by coaches.  If you do plyometrics, you get faster but risk injury.  You need to find the balance between improved performance and risk of injury.  However, interesting to hear that injury risk can be reduced with a programme of slow eccentric contraction exercises (but with associated loss of performance).  It would be good to have a video clip of a range of this type of exercise. 

    I think we would also benefit from a full statement on weight training.  Most sprint groups I know do Olympic lifts with heavy weights/low reps.  Do we need to re appraise this to encourage the slower movements that Keith discusses?

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