Training should replicate the coordinative, biomechanical, and bioenergetics demands of the sport, and whilst we can’t prepare for everything due to to unknown nature of sporting events, but if we see things repeatedly happen on the field during play, then we need to prepare as best we can for them. I believe that strength training should be planned, but as a coach, I think we can use research, monitoring, our own experiences, and the athlete’s experiences to guess how the athletes will adapt to stress, this is something you can read more about in Stuart McMillan’s blog post ‘just a dumb coach‘.
Kinetic variables (e.g. RFD, power, SSC, impulse and reactive ability) , which I believe are trainable in the weight room through effective planning and programming, as opposed to kinematic variables (base of support, centre of mass), which I would classify as coachable as they relate to the motion of a body. This will be covered in more detail in another post.
Rate of Force Development is an important variable in sporting actions. We want strong, powerful athletes who can produce large forces and power outputs, but the rate at which this can be expressed is just as important. Most dynamic movements in sport occur <200ms and can be classed as:
Ground contact time (GCT) during maximal sprinting during field drills, e.g. absolute speed days, as GCT during acceleration will be slightly longer due to overcoming inertia. The body is unloaded and to run faster athletes must generate high vertical forces, generate vertical impulse faster, and this is built through maximal strength and power training in the weight room, with exercises like squat variations, deadlift variations, Olympic lifts can increase force production, and jumps and hops performed in plyometric/movement sessions, with a vertical emphasis will work on short GCT, bridging the gap between the weight room and the actual event so to speak.
Depth jumps [depending on the drop height] – could be one of the most beneficial plyometric exercises, but I don’t see it being used as effectively as it could be. I think the reason is because the majority of athletes aren’t able to utilise the storage of elastic energy as efficiently to absorb the landing forces, and re-utilise the energy for the concentric component. This is evident in weaker athletes where I believe the majority should perform more drop landings to work on eccentric control, rather than the concentric component such as squat jumps and countermovement/box jumps. When we progress into continuous jumps, hops, and bounds the landing/decelerating mechanics are very poor, and are therefore just reinforcing bad mechanics repetition after repetition. It is far more effective, and safe to focus on single landings/jumps on the spot, rather than trying to add a linear/horizontal component before adequate technique has been mastered on the spot. However, with the stronger athletes, you can increase the intensity of the drills by increasing the eccentric component by holding dumbbells for the drop, get them to drop the DB’s on landing, and therefore perform the concentric ‘unloaded’ Other examples include increasing the height of the drop, or decreasing the height of the drop but increase the height of the concentric jump attempt.
Mini hurdle jumps – these can be performed out on the field, especially bilateral, and can be classed as short response. These will work on short ground contact time, so there is little hip, knee and ankle flexion (rate of stretch is short and fast) so the system is more stiff, but won’t produce high forces due to the magnitude of stretch being so short enough that high forces can’t be produced). So this exercise might not be classed as a ‘power exercise’, as I believe there are more beneficial exercises to produce maximal power, but can be used in the warm up or on a lower intensity day depending whether the emphasis is vertical or horizontal.
Long response >200ms – greater angles at the hip, knee, and ankle
Acceleration phase requires longer ground contact, and stride length increases from short to long, so the focus is on producing high horizontal force and impulse, this can be done through the resisted sprints/pulls we performed on the field, or broad jumps for example. See the following paper for more information Kawamori N, Nosaka K, and Newton RU. Relationships between ground reaction impulse and sprint acceleration performance in team sport athletes. J Strength Cond Res 27: 568-573, 2013
Single leg hops – I’ve seen a few coaches use this exercise, and it has a purpose as a long response plyometric, but also to increase eccentric loading. The GCT will be longer in duration as compared to a bi-lateral jump, and the higher/further the athlete jumps will determine landing forces to control. I feel most athletes would benefit more from bounds (either double leg or opposite leg landing), than hops as most can’t control the landing efficiently, and again links to the mechanical efficiency of the drill being stable and safe when landing especially.
Jump squats – Big power based exercise, research has shown produces maximal power more than power clean and pulls from power position, squat jumps, and back squat in a variety of athletic populations. Peak power has been shown at 0% body weight, so effectively it’s a CMJ, land, reset, go again. I see lots of coaches using this exercise, but maybe it can be used with a loaded bar at a certain % of 1-RM or an absolute value (40kg), so that the whole force-velocity curve is targeted depending on the phase of training. If it is used with additional load the landing mechanics must again be correct as landing forces will increase significantly as compared to performing with no external resistance. If the additional load is going up too, the exercise can change from jump squat to a squat jump (where squat down, pause 2-3s, then jump), this won’t result in as great a power output, but is still an effective exercise for concentric power, then it’s up to the coach to use different methods to incorporate the SSC into the training programme.
Olympic lifts – the Olympic lifts can also be classed as long response plyometrics due to the activation of the SSC during the transition from the first pull (RDL position) to the second pull (Power position). Also the catch position involves eccentric loading through rapid triple flexion, and can be compared to performing a drop landing, as athletes must absorb the load on the bar, depending if catching in the power position, or in deep front/overhead squat). I like to see the athletes performing ALL variations (from the floor, hang, power position), usually peak power and peak force is seen during lifts from the power position, as you can lift more load and velocity is at its highest during the second pull (triple extension).
Athletes must not only produce high forces, but be able to generate these in a short time. For example, an NFL athlete with a long training history, who trains for 4 weeks in the off season at a performance facility in the USA may not be able to significantly increase their force production through maximal strength training (due to their training history), but they may be able to increase their RFD, time to peak force, time to peak power, impulse, and force at 100ms for example (if the technology is there), moving their force-velocity curve up and to the right. It is not always the athlete that produces the highest force that wins, but rather the athlete who can utilise that force in a rapid manner during the dynamic movements (<200ms).
RFD differs from the weight room and the field. In the weight room, we load up the bar for maximal strength and power training, where you move a load with the intention to move it fast. During maximal strength training, the higher the load, the slower the speed, but as long as the intention is to move the load as quickly as possible, then RFD will improve. This will improve motor unit recruitment, neural firing frequency, neural activation, rate coding, and neuromuscular inhibition. Outside we use plyometrics to bridge the gap between the weight room and the field. So the athlete is now unloaded and using only body weight, where the velocity will be higher than in the weight room, but utilising the force interaction between the body and the ground. This is so that the force-velocity curve player is worked as a whole, because sporting actions require different qualities. If an NFL player requires maximal force and strength to hold off an opponent during play, they may also be required to accelerate 10-yds the next play, depending upon tactics and game situation, and these require 2 different strength/power qualities.
Impulse has also shown to be an important kinetic variable and can be calculated as change in momentum, or force x time. Greater impulse will be generated during the limited time and distance in which force is applied. Recent research by Rob Newton at Edith Cowan University in Australia has shown impulse to be a key factor in horizontal force production during acceleration in team sport athletes (see paper reference early in the post). Examples of exercises used to increase impulse could be sled pushes and resisted acceleration drills, where athletes have to produce more force during the first 10-yds, to set up good transition and absolute speed mechanics if the sport requires sprinting over these distances, most team field sport is between 10-20m.
The stretch shortening cycle (SSC) utilises the elastic properties of the muscle-tendon unit, during many sporting activities such as running, jumping and change of direction. This involves a rapid and forcibly lengthened pre-stretch of a muscle, followed by an immediate shortening in a reactive manner. SSC actions exploit the stretch reflex of the muscle-tendon unit, and it is important to decrease the “coupling time”, or the time from the end of the eccentric contraction, to the onset of the concentric contraction. Training the SSC can include plyometric methods (CMJ, depth jumps, hops, bounds, med ball throws), and heavy and ballistic resistance exercises (jump squats, and Olympic lifts), depending on the goals of the session, and/or phase of training. Med ball throws, and plyometrics are good power exercises due to the body working multi-planar, with proximal to distal sequencing and the action is explosive throughout the whole movement, so the load/implement is accelerated throughout a full range of motion, whereas in typical resistance training exercises (power cleans, squats), the load is accelerated, but then decelerates towards the end range of the movement (think the last 40%).