Speed Development Part 3: How to Train to Increase Rate of Force Development
This blog will cover the different physiological components, training methodologies, and proper sequencing of training when developing an athlete’s rate of force development (RFD). Here’s a quick review of RFD first. As defined in part 2,
RFD is a change in force divided by time
Strength can be defined as the ability to produce force and is the main determining factor of power output (Schimidtbleicher, 1992). It has also been shown that maximum strength markedly contributes to and strongly correlates to dynamic peak force and peak power at light (30%) and heavier loads (60%) (Stone, 2003).
As covered in part 2, when sprinting we have less than a tenth of a second to apply adequate force to not only negate our acceleration towards the ground but also then propel our body upward and forward. Since F = ma, acceleration of a mass such as our body is dependent on the ability of the musculature to generate force (Stone, 2002).
This image is a graphical representation of the force x time relationship of an untrained, heavy resistance trained, and explosive-ballistic trained subject. Don’t worry about the numbers as we aren’t going to focus on the details of the study, but I wanted to add this in as a visual representation of what was discussed in part 2. The heavy resistance trained individual can produce the most force, but has a poor RFD. In activities such as sprinting where the time window to produce force is less than 100 milliseconds, he would perform worse than a weaker athlete with a higher RFD, like the explosive-ballistic trained subject. Which is why acceleration capabilities are associated with the ability to attain a high peak RFD.
Also with increased maximum strength, a given load will represent a smaller percentage of maximum and therefor making it easier to accelerate. Think of your body as an object you are projecting. If I ask you to throw a ball weighing 10% of your body mass you could throw it farther than if I asked you to throw a ball weighing 15% of your body mass. Same thing is true of your body. If your body weight remains the same and your force producing capabilities increase, every time you have to accelerate your body when running you are accelerating an object that is now a smaller percentage of your maximum.
Physiological Adaptations with RFD Training
The majority of the remainder of this discussion on RFD development is a summary of a great research article by Gregory Haff and Mik Stone titled, “Methods of Developing Power with Special References to Football Players.” They did such a great job with the study I decided to summarize and discuss their work instead of trying to reinvent the wheel. Message me if you want a copy of the full study.
As an athlete increases maximum strength several power improving alterations happen simultaneously. They will have increased cross-sectional area of type II muscle fibers (an increase in the structural and contractile proteins in the muscles) and an increased rate of muscle recruitment by the nervous system.
Muscular Adaptations
Let’s start off by discussing the physiological components involved with power and RFD development. We will first discuss the muscular adaptations.
The two muscular adaptations we will discuss are:
Cross-sectional Area
Fiber Type
It is understood that an increase in a muscle’s cross-sectional area can contribute to increased strength gains and improve a muscle’s force producing capabilities. The type and speed of contraction used in training will influence the hypertrophic changes in the muscle and the relationship between cross-sectional area and power development.
Sarcomeres are the most basic contractile unit in a muscle fiber and with hypertrophic (increase in muscle size) growth they can either be added in series or parallel alignment within the muscle fiber. Sarcomeres added in series alignment will increase the velocity of the sarcomere shortening during contraction. This type of hypertrophic adaptation is the resultant of activities that stretch the muscle and significantly engage the stretch shortening cycle (SSC), such as plyometrics and olympic style weightlifting movements. Sarcomeres added in parallel alignment within the muscle fiber will result in a significant increase in force generating capacity and is the resultant of combinations of eccentric and concentric contractions.
Muscle fiber type is another large contributing factor as type II fibers have a greater force producing capability and faster contractile velocity. An individual’s ratio of type II to type I fibers strongly correlates with their peak power output. It is believed that the reason the type II fibers have a superior power output is that they have a higher cross-bridge cycling rate. In regards to training, it has been shown that muscle fibers have the ability to be shifted in response to the type of training undertaken. This shift can increase the overall percentage of type II fibers and therefore result in an increase force producing capabilities.
Neural Adaptations
Now to discuss the neural factors involved with power and RFD development. The three main neural factors we will discuss are:
Large motor unit recruitment
Rate Coding
Synchronization of motor unit recruitment
The type II muscle fibers discussed above are controlled by large motor units, which have a higher threshold and aren’t as easy to recruit. High threshold motor units are recruited when high force or high power output activities are done. However untrained individuals won’t be able to effectively recruit these high threshold motor units. With ballistic or explosive training, such as plyometrcis or Olympic style movements, an athlete’s ability to recruit these motor units sooner and more efficiently is improved. Also, as the body becomes more familiar with this type of training an athlete will have less neural inhibition from their golgi tendon organs.
Just as your muscles undergo adaptations when exposed to the stimulus of ballistic or explosive training, so does your CNS and motor units. Increased rate coding is an important factor because as the motor unit firing rate increases our ability to express high rates of force development also increases. The synchronization of motor unit firing is also improved with training. Typically recruitment of motor units follows the “Size Principle” which basically states that we recruit smaller motor units first and then larger motor units as needed later. As stated above, with appropriate training we can alter this recruitment pattern and recruit the large motor units sooner and more efficiently.
The graph below is a visual representation of the force-velocity curve. It is known that the faster our muscles shorten (right half of graph), the less amount of force they are able to produce. These adaptations discussed above will allow for a shift in this curve up and to the right as depicted by the blue line. This shift means that an athlete can produce more force at higher velocities, which will improve performance in most dynamic sports.
Now that we know why a high RFD is needed for athletes and the physiological adaptations that occur when training to increase RFD, it is finally time to discuss the appropriate sequencing of training and training methodologies to increase RFD.
Sequencing of Training
Periodization is defined as:
“A logical systematic integration and sequencing of specific training factors into mutually dependent periods of time, which are designed to result in an optimization of very specific physiological and performance outcome at predetermined time points.”
Each training block will focus on a specific fitness component, this doesn’t mean it will be all that is developed during that training block, but it will be the focus. Training blocks will also be performed in a specific sequence so that each block potentiates the preceding block. The physiological adaptations from the current block should prepare the body for the preceding stimuli and therefore optimizing adaptations.
It is important that the training activities of each block are implemented correctly to maximize muscular adaptations that facilitate power generation. Too often in power sports such as softball you see coaches having their athletes performing 2 mile conditioning test at the beginning of camp. This type of ancient thinking will lead to less than optimal training and athletic development. The distance running to train for such a test will result in a shift of the muscle fibers towards type I fibers, which will result in decreased RFD, peak power-generating capacity, and maximal strength. Remember coaches, just because you were a good athlete and you had to do something when you were an athlete, does NOT mean it is what is best for your athletes.
Work by various researchers suggests that power development should begin with training to increase cross-sectional area, followed by a transition into the maximization of muscular strength, and finally power development. The number one key factor dictating how powerful an athlete can become is their level of muscular strength. Increasing muscular strength will increase an athlete’s ability or capacity for power development.
The million-dollar question is how long should you spend developing each of these fitness components before transitioning onto the next one? There is no one answer for this as it is dependent on many variables including: the development level and ability of the athlete, the density of training, the performance characteristics of their sport, the time-line of training, and many other factors like training residuals. A coach must analyze each situation and make a judgment call on what they believe to be best for their athletes. They will analyze the current abilities of their athlete, how often they will be able to train, the time-line of their training and so forth to make their decisions. A weaker athlete will most likely spend a lot longer time developing CSA and strength before advancing to power development training. In the collegiate sector the annual plan is developed primarily based off the teams schedule and time-line. However I would still want my less developed freshman spending more time in a general physical preparedness phase than my seniors.
There are some guidelines however and suggestions we can take away from research. We know the primary focus needs to be strength until an athlete has a good base of strength. Cormie et al (2010) showed that the power output of athletes who were weak (squatted < 1.5 x body weight) benefited more from activities that targeted primarily maximal strength, than training targeted towards power development. In another study Cormie showed that athletes who were strong (squatted > 2 x body weight) had superior adaptations to 10 weeks of ballistic training than did the weaker athletes. Mike Stone has always preached that until an athlete can squat twice their body weight they are weak and the training focus should be strength development. Now remember these are just guidelines, but they do have research backing them up.
Keep in mind that if training is done correctly it is highly unlikely that only one training factor is improved at a time. Power should improve during a strength phase and strength should improve or at least be maintained during a power phase. The majority of athletes I work with are relatively weak and undeveloped high school kids, so I will spend a lot of time developing strength. However while I’m working on strength development I will also be teaching them base level plyometrics and movements in order to prepare them for later phases. While the focus is strength, they will also be learning how to land properly, to perform a proper countermovement, basic jumps and hops, and developing acceleration and deceleration mechanics. On the other side, as an athlete moves into a power development phase, they still need to heavy strength train 1 or 2 times a week to prevent decreases in their strength levels.
Power Development Training Methodologies
There are a wide variety of training activities coaches use to increase an athlete’s power and they can all be effective. I have always said that these different activities are just tools and that there are not good or bad tools, just good or bad ways to implement these tools. When developing power, common denominators between all of them are that they incorporate fast contractile rates, maximal effort is necessary, and most of them incorporate the use of the SSC. The power development training methodologies I am going to discuss include:
Olympic Style Weightlifting
Plyometrics
Explosive Exercise Training
Strength-Power Potentiation Complexes (SPPC)
Olympic Style Weightlifting
Weightlifting movements undoubtedly have been proven to improve speed, power output, maximal strength, RFD, and agility. This should come as no surprise as when they are done correctly they result in high power outputs as they incorporate fast bar speeds, the SSC, and triple extension of the ankle, knee, and hip joints. The weightlifting movements can be a very beneficial tool to use as one can provide various stimuli in different phases by using a variety of derivatives to manage stress and varying intensities to alter bar speed and power output.
The primary concern using the weightlifting movements for power development is that time must be spent in order to become technically proficient at the movements. This takes time, adequate equipment, and proper coaching, which aren’t always a luxury all coaches have. If you aren’t proficient at the movements as a coach or at least have a firm understanding of how to teach them, it is probably best that you don’t use them with your athletes. It can also be a difficult task to teach a whole team at once without assistant coaches who are experienced.
Time is another issue, especially in the private sector. I often get parents hiring me to get their kid ready for season in 3 months and it would be foolish of me to spend that short amount of time trying to teach them the movements when I can use other methods for power development. If I am going to teach them the clean, what I will typically do is use barbell complexes as part of the warm up during their general prep phase. Barbell complexes will help engrave proper technique, so that they will be ready to start adding weight in the preceding phase. They are also time efficient and an effective form of warming up for a lift.
Plyometrics
A plyometric exercise is defined as an exercise that incorporates the SSC, which is a rapid stretch of a muscle or group of muscles, immediately followed by a concentric contraction. The three phases involved are the eccentric phase (muscle lengthens), the amortization phase (short time between eccentric and concentric phases), and the concentric phase (muscle shortens). The rapid stretch during the eccentric phase will result in increased force output if immediately followed by the concentric contraction. This is a result of our body’s ability to use stored elastic energy, the potentiation of the contractile machinery, the interaction between the series elastic component of our muscles and the contractile machinery, and the engagement of the muscles reflex action of the muscle spindle fibers. Plyometric training has been shown to increase power output and RFD and can also result in increased neuromuscular control and movement efficiency during high impact activities such as cutting and landing.
I’m not going to discuss different plyometric drills you can use because that information is readily available in many books and the Internet. However I do want to discuss some considerations to keep in mind. Plyometrics are extremely strenuous on the body and taxing on the CNS and shouldn’t be used with weak or novice athletes. The NSCA recommends that athletes should not participate in advanced plyometrics such as depth drops until they can squat 1.5-2 times their body weight or squat 60% their body weight for 5 reps in 5 seconds.
Also, without adequate strength plyometrics lose their effectiveness. A weak athlete will not have the strength to quickly absorb the large deceleration forces during the eccentric phase and will have too long of an amortization phase and as a result lose most of the benefits of the SSC. Similar lost of effectiveness occurs when performing plyometrics in a fatigued state as the speed of the movements decrease.
Explosive Exercise Training
Typically explosive exercise training is doing resistance-training exercises with a decreased relative intensity at high speeds. Squat jumps are an example of this and an effective exercise to increase lower body power output, but shouldn’t be done until an athlete is proficient with the back squat. The intensity at which power output is highest varies between athletes. Relatively weak athletes will produce peak power outputs with no load, while strong athletes will typically have peak power outputs at loads between 30-60% their 1 RM.
Strength-Power Potentiation Complexes (SPPC)
Strength-Power Potentiation Complexes (SPPC) are also known “Complex Training” and is the pairing of a high force or high power exercise followed by a high power or high-velocity movement such as a plyometric. A popular example of this is to perform a popular example of this followed by a jumping plyometric exercise such as a vertical jump. The high force exercise can cause a post-activation potentiation (PAP) response resulting in improved power output and performance in the preceding high-velocity movement. The time between exercises necessary to have a post-activation potentiation response will vary based off the intensity and volume of the exercises and the strength levels and conditioning of the athlete. This type of training is more effective when performed by stronger athletes (back squat > 2 x bodyweight) whom have a higher percentage of type II muscle fibers. Another version of SPPC training, which has recently gained popularity by Cal Dietz, is called French Contrast Training. Read his book Triphasic Training if you want to learn how he incorporates it.
Conclusion
Now you should have a better understanding of the adaptations that occur allowing for our muscles to produce more force, how to properly sequence power development training, and some popular training methods for power development. I know this blog is really long, but I believe it has a lot of valuable information in it and I really appreciate you taking time to read it. Please leave any questions or comments bellow and I will get back to you as soon as possible!
