Hamstring Injury Prevention: Elite Coach Cast Part II; Henk Kraaijenhof

Continuing part I of this great series on hamstring injury prevention, we have Henk Kraaijenhof, an elite former sprint coach from the Netherlands, who needs no introduction for many. Henk’s credentials include coaching sprint sensations Merlene Ottey and Nelli Cooman, amongst others. He has coached athletes to elite times, even in their 40’s, and is one of the most intelligent coaches I know. His presentation on sprint speed I saw last year at the Central Virginia Sports Performance Seminar blew me away, and I left with a whole new way of thinking about how fast and slow twitch athletes tend to respond to training, reaction training in warmups, and optimal power indexes for strength work.

We’ll finish out this series on hamstring injury prevention with Henk’s take on the topic, which is again, a must read for all strength and speed professionals.

Hamstring Injury Prevention with Henk Kraaijenhof

As a coach in track and field, mainly sprints and explosive events, my teachers throughout the years taught me that the hamstring strain was the result of:

Lack of flexibility (temporarily or structural – short hamstring syndrome)
A disbalance between the strength of the quads and the strength of the hamstrings
A leg length difference
Cold environmental temperature or lack of warming-up
Lack of proper sprinting technique
Some more small factors that may be related to hamstring strains, like pelvic imbalance, blocked SI joint, piriformis syndrome, tight fascia, etc.
Fatigue

Let’s take a short look at all these factors:

If lack of flexibility would be the main cause, the most flexible athletes should have less hamstring strains and stretching the hamstring would be the proper solution. Unfortunately I found this not to be the case and research found no strong relationship between stretching and hamstring injuries.
The strength balance between Quads and Hamstrings (Q/H ratio) is very difficult to prove. In isometric testing: the Q/H ratio depends on the knee angle one is using for testing. In isokinetic testing: the Q/H ratio depends on the knee angular velocity one is using for testing. The Q/H ratio changes considerably when knee angular velocity changes.
This would mean that athletes with stronger hamstrings should have less hamstring strains and that strengthening the hamstrings would be an adequate solution. But again, I did not see it.
Leg length differences: That depends on your cut-off value, since it’s hard to find athletes whose legs are exactly the same length. A solution here depends on where the leg length difference is coming from: from a real leg length difference or from a pelvic torsion. Sometimes athletes are wearing insoles to neutralize this problem.
Personally I have seen athletes getting into the blocks without any warming-up at all and they ran a PB without any problems while others, even at very high temperatures (I use to work in the Middle East for some years) and a proper warming up still strained their hamstring.
Lack of proper sprinting technique: I found it remarkable that some athletes often suffered from hamstring strains, while others never had any problem with it, and yes, the athletes with a better sprinting technique (but this will probably raise a new discussion) seem to have less problems.
There are some other factors to consider, but it is hard to see if this factor has any relationship with hamstring strain, or if it is the cause or an effect of hamstring strain. It is easy to detect a strength or flexibility imbalance in one hamstring when you just strained it a few days or weeks ago. Or it might just an unrelated coincidence or they may be both different expressions of an underlying problem. Hard to tell.
Fatigue: keep on reading

But my idea developed in another direction: I asked myself some questions:

Who strains a hamstring? Let’s look at track and field: you seldom see hamstring strains in shot putters, race walkers, marathon runners, or even 800 meter runners. The sprint events (also including hurdles and relays) is where it happens.
When do they strain a hamstring? Seldom at the start or during the acceleration phase, unless the strain was already present at that moment, e.g. from the warming-up or from the previous round.

Most of the time the strain appears at maximum speed or when the sprinters tries to maintain the maximum speed despite the fatigue or tries to decide the race. In the 100 meter it is mainly somewhere between 50 and 100 meter and in the 200 meter most of the time between 50 and 100m as well, at the end of the curve. Even in the 400 meter, most pulls are in on the backstretch where the fastest 100 meter split is produced.

Of course we also find hamstring strains in soccer players and football players, (and again less often in tennis players, considering the short distances)

Why would this be? And maybe here is the solution – as coach I am more solution-oriented than trying to scientifically establish the exact etiology of the injury, but it certain helps to know the mechanism(s) though which it happens.

The maximal sprinting speed is the result of a large stride and a high frequency, which places special demands on the hamstring.

The hamstring is not one muscle but consists of the semitendinosus, semimembranosus (mono-articular-only runs over the knee joint) and the biceps femoris (biarticular – runs over knee as well as the hip joint and hip). The hamstring group is very active and then mainly eccentrically, at the last part of the swing phase. In the 1970’s I still was taught that the hamstring works concentrically, bringing the foot towards the glute, in the first part of the swing phase! So one had to perform a lot of drills like butt-kicks.

So the hamstring group works eccentrically at maximum speed of contraction, alternated with relaxation and simultaneously running more than 11 meters per second and fatigue setting in. This may cause problems of the biceps since it long and short head are innervated from two different segments and they have to be synchronized perfectly. At the other hand, looking at the fiber composition of the semitendinosus and semimembranosus, they contain more slow twitch fibers than the biceps femoris and they may have problems contracting and relaxing at that very high rate and with that high eccentric forces acting.

And of course herein lies why most preventive exercises don’t really work, because they do not train the hamstring specific to work eccentrically at high velocities with a high frequency!

Static stretching does not prepare for this kind of load, nor do leg curls in an exercise machine do that!

Looking at team sports: a prognosis of hamstring injuries is more difficult than in track, only since there is bodily contact and many other factors to consider.

We can, but it’s not easy, with the use of EMG, one of my mentors, developed simple and practical methods to detect the risk of hamstring injuries.

The only and, as far as I am concerned. best solution is to prevent hamstring injuries by three important factors:

A set of simple specific preventive exercises that I developed throughout the years, for sprinters but also to be used for team players I used to work with some of the world’s best soccer players as well.
Testing with EMG on a regular basis, especially the athletes or players that have a history of hamstring problems or are vulnerable for hamstring problems.
Working with the Omegawave system, some parameters especially related to fatigue of both nervous systems (ANS and CNS) were a great help in avoiding the dangerous form of fatigue, which lead to an increased risk of injuries. The ”famous” CNS fatigue is now detectable and obviously can lead to disturbances in coordinating the hamstring activity at speed and high intensity fatigue. Research has shown that the status of the CNS has a strong relation with injuries in general. In other words, make sure that the CNS is well-rested or optimally charged before engaging in maximum intensity and maximum quality workouts like sprinting.

I am not too fond of the many preventive therapies that are used in the US since I really cannot see US athletes being significantly less injured than athletes from other countries in the same event, as a matter of fact, but I haven’t seen the numbers, I think it is even worse.

Ask any former East-Block athlete, who despite the high performance level and the sometimes primitive training facilities seem to suffer a lot less from injuries, I have been observing them and their coaches for a long period of time. And what always surprised me was their low frequency of injuries despite the hard work they did. They spent a lot of time on decent recovery and therapy after injury, but there weren’t three or four therapists around them on the track.

About Henk Kraaijenhof:

Henk Kraaijenhof coaching credentials include Nelli Cooman, Merlene Ottey, Troy Douglas and Tennis star Mary Pierce. His specialties are the physical and mental coaching, in particular stress and stress management and the methodology or training. When you consider both Ottey and Douglas ran world class times in their 40’s, something is working.

Henk Kraaijenhof currently works for Vortx and his blog is helpingthebesttogetbetter.com.

He has published work in performance, training systems and protocols for elite athletes and has also conducted research in the development and application of scientific training systems. Henk is also involved in scientific research projects in human sports performance in Norway, Estonia, Italy and the Netherlands. He is currently also working as a mentor for the Olympic coaches and Olympic talent coaches in Holland.

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