My friend James Smith once remarked that getting strong is like falling out of a boat and hitting water, and that speed is a far harder ability to develop. The need for well selected, loaded and executed exercises is vital in speed development, and the price of inaccuracy is far higher than for the development of other abilities like strength. For this reason one of my primary areas of interest as a coach is the development of speed in rugby athletes.
As you may recall from previous blog posts of mine, I believe that specialised strength development is an important element in sprint training due to the ineffective transfer of general barbell strength training programmes to sprinting speed beyond the first few years of training. Beyond this stage such training merely lays the foundation for the use of more specialised exercises which share greater kinetic and kinematic similarity to the sprinting action.
What makes an exercise more or less specific to sprinting?
One of the major criteria of dynamic correspondence- what makes an exercise more specific to a sporting action, and more or less likely to transfer to improved performance- is the primary direction in which force is applied. For this reason, the direction of forces applied during the sprinting action has been a keen interest of mine, as this has a significant influence on the type of exercises selected in my programmes and how they are executed.
Here is a short summary how my previous understanding of maximal velocity sprinting biomechanics went:
- Speed is at its most simplistic a horizontal displacement of the centre of mass in minimal time, which arises of a resultant horizontal force being applied to the body. Maximise horizontal propulsive force and minimise horizontal braking force and we should have a faster athlete.
- Beyond providing sufficient flight time to reposition the limbs and fighting the effects of gravity on maintaining posture, vertical force was not a big limiting factor in maximal sprinting speed.
- Research suggests that the best sprinters tend to have the smallest vertical displacements of the centre of mass, and newer research from JB Morin suggests that (at least for rugby athletes) that vertical jumping ability was no great predictor of maximal velocity sprinting, whereas horizontal sprint power was a strong correlate.
The end result of this course of thinking was that I essentially disregarded vertical force production and placed far more emphasis on horizontally orientated specialised strength development exercises in the programmes I use for my players and clients. Lots of stuff like plyometric bounding for distance, dynamic band hip extensions, explosive step ups, hip thrusts etc. However this year I have changed my mind somewhat.
I’m slowly changing my mind
This year I have been lucky enough to meet and learn from top UK Sprint Coach Jonas Tawiah Dodoo on two occasions. The first was an in-house staff training session at a Premiership football club, and the second was when Sam Portland and I made the trip down to Lee Valley to watch Jonas train his group of athletes, which includes UK 100m Champion CJ Ujah. One of the major lessons I took away from Jonas is that vertical force may be more important than I had suspected….
It’s a bit of a cop out, but the first reason is when somebody is a better coach than you, and consistently produces faster athletes than you, you pay attention! And vertical force is a key attribute that Jonas aims to develop at maximum velocity in his athletes.
The second reason is based on research conducted by Southern Methodist University, presented by Jonas and Dr Paul Brice which suggests that it is not horizontal force, but vertical force that is the major distinguisher for sprinting speed both within individuals and between individuals. This means that if you as an individual want to increase your sprinting speed, you will probably have to increase vertical force production. It also means that if somebody is running faster than you they are probably producing more vertical force.
Interestingly, the first 50% of vertical production during the stance phase was the big difference between slower sprinters and faster sprinters. There was no significant difference between sprinters for vertical force production during the second half of the stance phase.
What do I now think?
This suggests to me that at top speed, because of the braking effects of friction acting against the body and the increased rate of forward rotation of the body upon contact, vertical force may be the only real way for the body to produce force without lengthening ground contact time or falling forward, which will have a detrimental effect on joint positioning in subsequent steps. Resultant horizontal force may be the aim in displacing the centre of mass, but perhaps we can only achieve this via more vertical force production with the aim of increasing the total force vector as a whole.
Second, because of the ground contact times and joint positions associated with the first 50% of ground contact time i.e. a near vertical lower limb and barely five hundredths of a second, the forces produced prior to ground contact may be more important than I had anticipated. The ability to drive the lower limb into the floor as fast as possible then create maximal stiffness, is probably more important than the ability to drive into the floor during ground contact.
Consequently I am inclined to question the value of specialised strength development exercises where the athlete may be able to solve the task via increased force production through ranges of movement that do not correspond to that initial 50% of ground contact (why train something that doesn’t separate good athletes from average ones?). Likewise in future I may place more emphasis on exercises that train the velocity at which the limbs are switched or the ability to create maximal stiffness prior to and upon ground contact e.g. hurdle bounds, reactive ankle jumps etc.
My primary instinct however at this stage is not to swing in completely the opposite direction and flip my programming and coaching on its head. This is because another key lesson I took away from Jonas and Paul is that sprinting is an art of balance: between stride length and stride frequency, between ground contact time and force production, and my guess: between horizontal and vertical force. Rather than completely remove certain exercises from my programming, my response will probably be to use more of a blend in my future programming.
Happy new year!