The work of Frans Bosch and John Pryor has created a new discussion around strength training, coordination, and motor learning over the past few years. Bosch has been a thought leader, while Pryor has taken the application of the concepts to new levels in his work with Japan and Fiji rugby. Both are coming to the US in December for a series of seminars, and we got them to join the GAINcast for a two-part interview on a wide range of topics. Part 1 of our interview looks at how their work has evolved and how they began working together, transfer of training, the role of traditional strength training, and misinterpretations of Bosch’s work. Read more
Robust running is a topic that has been well covered by John Pryor on the HMMR Media website and classroom. It can be thought of as the ability to maintain consistent rhythm when negotiating different tasks or environments. By reinforcing a positive running posture, athletes build the ability to execute technical skills when presented with environmental perturbations such as defensive players. Training athletes to better handle such perturbations helps them execute skills at higher speeds in wider range of positions.
The constraints-led approach popularized by Frans Bosch’s book Strength Training and Coordination: An Integrative Approach is one way of developing this positive running posture. This article will look in more detail at this approach in theory and practice.
Why use a constraints led approach?
The idea of a constraints-led approach is to add variability to a movement through changing the way the task is performed or the environment where the task is performed in. By doing so, you can reinforce the stable, economical components of a movement. To use Bosch’s terminology from motor learning, a variation in the task or environment can be thought of as a fluctuation and the economical component of a movement an attractor. Attractors are the stable parts of the movement that should appear in all situations. Fluctuations are the parts of the movement that adapt to the ever-changing environment such as a rugby match or the variation of a hitting a baseball pitch. Hence, the deeper an attractor is ingrained, the more stable that component will be when changes in the environment occur.
When looking at running, Bosch identifies eight key attractors in his book:
- Hip Lock (swing leg hip higher than stance leg hip);
- Swing Leg Retraction (timed hip, knee and ankle extension just prior to ground contact);
- Foot Plant from Above (foot strike towards the ground as parallel as possible to direction of GRF);
- Positive Running Position (legs more in front than behind, tall posture);
- Keeping the Head Still (minimal vertical head movement);
- Upper Body First (changes of direction initiated from shoulders/upper trunk);
- Extending Truck while Rotating (upper body rotation without effecting pelvis position); and
- Distributing Pressure when Deceleration (minimize loading on the knee).
By implementing a constraint in the task or environment, an athlete is put in a position to reinforce a certain attractor or to help the athlete find a movement solution. Instead of trying to coach minute details during sprinting, the constraint provides intrinsic feedback to the athlete. This type of intrinsic feedback would be labelled as knowledge of result information (KR), which I’ll explain a bit more below.
When compared to other types of feedback, KR has some big advantages. Augmented KR, such as giving the athlete feedback about how fast they ran, is another type of feedback. Providing more standard coaching feedback would be labelled augmented knowledge of performance information (KP). As Bosch states, “movements learned with a great deal of augmented KP feedback (i.e. coaching & correcting) are less stable and less reliable especially in stress situations – for instance during competition.”
Examples of constraints for sprinting
As stated above, task and environmental constraints provide intrinsic KR feedback that may ‘stick’ better during high pressure situations. Here are some examples for how constraints can be introduced into the task or environment to achieve this result.
- Task constraint: stick run
Often while running, athletes rotate around the longitudinal axis which impairs running efficiency. Instead of trying to coach the athlete not to rotate at toe-off with augmented KP feedback, providing the athlete with a stick to hold on the athletes back can give them KR feedback.
Athletes can simply hold a stick on their back as they would a barbell during a back squat. Another alternative is holding the stick overhead. The only coaching cue is to keep the stick as still as possible while sprinting. The athlete then gets intrinsic KR feedback by feeling whether the stick is moving or not. If the stick is kept still while running, then rotation has been minimized and body position has been changed for that repetition.
- Environmental constraint: mat run
Coaches can add an environmental constraint by randomly placing pieces of soft matting approximately 4-6cm thick along the ground for an athlete to sprint over. With this changed environment, the athlete has to find a movement solution to sprint over various densities and heights of ground without tripping over and falling.
In essence, three attractors of running are needed to perform this sprint successfully; swing leg retraction, foot plant from above and positive running position. If a forward knee position of the swing leg and a foot strike from slightly greater height aren’t achieved, then it is likely the athlete will kick the edge of the mat and trip. Likewise, if sufficient stiffness isn’t achieved through the timing of extension through hip, knee and ankle at ground contact then the athlete will have a hard time navigating the different surfaces to maintain their speed.
Game-specific constraints in training
Athletes don’t play the game with a stick on their back, but game-specific constraints can also be introduced into training to help develop robust running skills.
A recent research paper has investigated the effects of carrying a rugby ball on sprint kinetics, which provides a good example of how in-game constraints also affect running. When carrying a ball with two hands, maximum velocity was negatively affected and athletes saw slower split times after 20 meters compared to running without a ball, however were able to accelerate to 20 meters just as well. Carrying the ball with one hand saw negative effects on acceleration, but similar maximum velocities reached when compared to running without a ball.
The reasons for the changes in acceleration and maximum velocity were due to changes in the mechanics of sprinting with each constraint. The negative acceleration effect seen while running with the ball in one hand appears to occur due to a possible asymmetry in the upper to lower body counterbalance. i.e. the arms both don’t drive straight, rather the arm carrying the ball tends to drift across the body disrupting normal sprint mechanics. In contrast, sprinting with the ball in two hands may have created an upper to lower body counter balance similar to that of sprinting with no ball as there were no significant differences in split times between ball in two hands vs no ball conditions in the first 20 meters.
As you can see, athletes might want to hold the ball in different ways in order to accelerate and reach high speed optimally. Ideally, an athlete would start running with the ball in two hands and then transfer it to one hand at approximately 20 meters. However, this isn’t always possible due to the unpredictable nature of sport where you may have defenders close by that require an evasive maneuver to beat. Some tasks simply require two hands (picking up a ball, receiving a pass, giving a pass, etc.) and some call for one hand (top speed on a runaway, while fending off an opponent, etc.).
Therefore athletes should be able to easily switch ball positions while running, and this can be a constraint introduced into running drills to help ensure attractors express themselves in all varieties of running. Using a ball during speed training knowing that you can reach similar force, velocity, and power numbers as sprinting with no ball during different phases of the sprint. The addition of the ball in hand(s) can potentially be used as a specific task constraint or paired with other constraints in a session to reinforce certain attractors prior to sprinting with a ball.
In the end, the goal of athletes in all sports is to have options. John Pryor has talked about how he trained rugby players to create options: they are a more potent offensive threat if they run in a way that gives them the option to pass, kick, or turn at all times. This is the end goal of robust running. If a constraints led approach is something that interests you, check out John Pryor’s work on the HMMR Media classroom. He has great examples of how you can use different environmental and task constraints to reinforce certain attractors of running.
Welcome back to another edition of Sports Science Monthly. This month, we take a closer look at the timing of injury prevention training, mental fatigue, antioxidants, max testing, agility, chocolate milk, and several other topics. Read more
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