Strength and Power.docx

Strength and Power ***5.1: Non-muscular adaptations to strength training*** - Non muscular adaptations = neural adaptations. These occur between the brain and the NMJ. - Golgi Tendon Organs: refers to a proprioceptive sensory receptor that detects changes in muscle tension, located at...

Strength and Power ***5.1: Non-muscular adaptations to strength training*** - Non muscular adaptations = neural adaptations. These occur between the brain and the NMJ. - Golgi Tendon Organs: refers to a proprioceptive sensory receptor that detects changes in muscle tension, located at the musculotendinous junctions of skeletal muscle - Autogenic Inhibition: a reduction in excitability of a contracting or stretched muscle, largely caused by the inhibitory input arising from sensory receptors within the muscle. Literally means the muscle generates its own inhibition. - Reciprocal inhibition: the process whereby the antagonists of a joint action relax to accommodate contraction of the agonists acting on that joint - Interneurons: creates neural circuits, enabling communication between sensory or motor neurons and the CNS. Involved in reflexes, neuronal oscillations and neurogenesis. - Co-activation: when the brain fires both the agonists and the antagonists during a movement cause it doesn\'t know how to stabilise the joint. As we train, the nervous system adapts and stops firing the antagonist muscles as it realises that it no longer needs them during movements where they are not the primary movers. As we train, reciprocal inhibition improves, reducing co activation. - Our GTO\'s detect excessive force and apparently act as a protective mechanism to stop the muscles generating more force than what they can withstand. High force on the tendon generates a negative feedback loop, inhibiting the muscle from generating more force = more force the muscle tries to make, the more the GTO says nope. As we strength train, the amount of inhibition to agonist diminishes, allowing the muscle to activate more.   Reduced Recurrent inhibition from interneurons - Interneurons have more of a contradictory role. The more we try to activate, the more they try to get in your way. They try to help you balance out the force by applying just enough but not too much. - They are part of, but have a separate neural pathway, to the motor nerve, this is called recurrent inhibition, meaning turning back so as to reverse direction - Interneurons also get less sensitive with strength training.   Increased Firing Frequency 1. A single pulse from the motor cortex of the brain, and down the motor nerve to the muscle is called a "twitch" (a) 2. When another twitch is sent down the nerve and activates the muscle before the previous twitch can relax (a+b), the pulses compound into a "tetanus", increasing the force and the rate of force development (c). 3. While tetanus is still not stable force, if so many twitches are sent down that the force stabilises into what we think of as a contraction, the contraction is said to be "fused (d).   - Slow twitch fibres tend to fuse with twitches as low as 10Hz, fast twitch can fuse at 40 Hz. - At a frequency over \~60 Hz (\~30 Hz in ST fibres), maximal tension is produced, beyond which higher frequencies of stimulation have no effect *on force*. However, at stimulation rates of \>60 Hz, the *rate *of rise in force is greater. This is a characteristic of high-power athletes who can hit firing frequencies of 120 Hz. The faster firing frequency doesn\'t create more force, but generates it faster.  - The firing frequency of the nerve and the muscle that can accept it is called "rate coding" and is particularly important to speed training   Improved recruitment patterns (synchronisation) and improved activation patterns - If we start to shake when lifting heavy, this is a result of the muscles trying to pull together and synchronise, in order to generate enough force. - Asynchronous contraction means that each MU fires at different times, one is turning off whilst the other on and whilst it results in less force it tends to be more smooth, but synchronous has them going altogether, all at once but it can be a bit choppy. - Both have pros and cons. - there is a lot of timing that goes into the optimal application of force, muscles turning on and off at optimal times. Improved activation patterns from the motor cortex allow for improvements in the timing of firing of agonists and synergists.   ***5.2: muscular adaptations to strength training*** - Meaningful muscle growth requires challenge and stress. - Training for specific outcomes alters the way your muscles adapt. - During resistance training, both Type I and II muscle fibres are recruited, presenting them with a potent stimulus for adaptation. While both fibre types typically undergo an increase in cross-sectional area, Type II fibres generally undergo greater hypertrophy. But it is the pattern of neural stimulation that dictates how fibre type adapts. - Regular strength training involving activation of high-threshold motor units will more easily recruit Type II fibres, and with regular strength training these fibres transition from the basic Type IIb fibres towards the more oxidative (enduring) form Type IIa fibres. This increases the muscle\'s tolerance of this type of loading allows for increased volumes of training. De-training appears to reverse this transition, and transform Type IIa fibres back towards Type IIb fibres - In pennate muscles (those where the muscle fibres align on a different angle to the tendon) which generally produce higher force production than other types of muscle, the angle of pennation during contraction can be increased with strength training. Such increases in angle of pennation during contraction (towards the 'optimum angle' of 45^o^) then allow for greater increases in muscle cross-sectional area and the production of greater force. - Lower pennation angles tend to be better for speed. So the hamstring is not pennated at all, the fibres in direct line with the tendon allowing for sprinting speed. The deltoids have many pennations, making them much better at force   Hypertrophy - Product of strength training. - Not as essential to strength output as once thought. - Hypertrophy is a result of the contractile elements in a muscle getting larger and the muscle fibres themselves will then grow as a by product of this. - There is also an increase in the number of myofibrils within the muscle fibre, aka proliferation. - Some people will have more muscle fibres than others, but that is the result of genetics, not hyperplasia. You can\'t even change your basic fibre types much (i.e., Type I or Type II). While swapping between IIa, IIb, IIx, etc. happens with training, you can\'t change Type I into Type II, or visa versa. Great marathon runners, rugby props, and sprinters are more so born that trained.    Increase in the number of sarcomeres - ST is an anabolic stimulus and triggers the body to promote protein synthesis. This stimulus tips the balance in favour of synthesis instead of breakdown. - The increase in contractile proteins = increase in the number of sarcomeres and note that these are typically added to the external layers of the myofibril and in 'parallel', giving us that increase in diameter, not length. So what we end up with is more cross-bridges. Because each cross-bridge is capable of generating a certain amount of tension, increasing the total number of cross-bridges should lead to greater force production, so as a result, hypertrophy usually gives us increases in strength.   Muscle Damage and Satellite Cells - Remember the micro-trauma and inflammatory cytokine response mentioned in the Ted-Ed video? Well this inflammatory cytokine response awakens the muscle satellite cells which are usually dormant. So, when you generate mechanical overload through strength training and induce micro-trauma, these satellite cells respond. Fuses to the cell to restore the integrity of the muscle fibre.   Muscle Tendons. - Tendinous stiffness increases following high-intensity strength training. This affects the time required to stretch the series of elastic components within a muscle, and therefore affects the recruitment rate and rate of force development to enhance the rapid application of force.   ***5.3: traditional methods of strength training*** - Traditional models are based on research done decades ago. - The old-school model of resistance training for muscle strength uses the traditional 3 sets of 12 repetitions at moderate-high loads, slowly re-assessing the load over time in order to continue progression. This model suggests that neural mechanisms play a role initially followed by a larger contribution from muscle hypertrophy.  - Additionally, there may be some degree of independence between hypertrophy gains and maximal strength gains instead of this old-school progressive model of strength development. Instead it appears that not only is there an imperative to intermix volume with high-load strength training in order to maximise hypertrophy, but there is also a need to be more responsive to the individual in terms of load and volume adjustments at more regular intervals. In more plain language, this means that 1. **hypertrophy requires strength**, and 2. we shouldn\'t be using the method of \"keep trying to do more reps at \'x\' weight until you can do 12, and then increase the weight to the point where you can only do 8; keep doing that new weight until you can do 12\...\" (i.e., adjustments need to be much more frequent).  - The information on Progression Models in Resistance Training for Healthy Adults from one of the most prominent sources in the field, the American College of Sports Medicine, suggests that **3 sets of 2 to 6 repetitions at approximately 85% 1RM or higher** is the necessary stimulus for increasing muscle strength. In theory, this ticks the boxes of \"multiple sets of low volume of high intensity\".  - This prescription is evidence-based and synthesised from a long track record of studies employing basic exercise prescriptions. As such, while it may still work, it could be considered quite conservative, and is unlikely to be optimal due to what we know about the need for variation, cyclical loading, and recovery in order to optimise supercompensation. - Additionally, this conservative or generic mould for strength training may actually limit adaptation, specifically with regard to sports performance. The further devoid from a sport-specific strength application that a training modality becomes, the less transferable any strength gains are. In a similar vein, if you want to improve your 1RM squat, then squatting at your 1RM with very low volume is going to be more effective than doing leg press at your 3RM despite the similarities in joint actions and muscular recruitment.   ***5.4: contemporary methods of strength training*** \*these models require 4-6 days of training and aren\'t practical for S&C environments   5x5 Method - High intensity - 5RM or 87%1RM - Only 3 training days per week with 1 day off between sessions. Big lifts are split across 3 days. - 5 reps, 5 sets though some exercises may only have 3 if they are harder, ie: deadlift. Or could be a 3 x 3   Westside - Derived from Russian and Eastern European weightlifting programs. - 4 day split, 2 upper and 2 lower, a dynamic effort day and a max effort day. - Max effort: Trained with a large number of sets (8-12 sets) and generally very few reps (1-2 reps) at near maximal intensity (90-100% 1RM) - Dynamic Effort: Similarly, trained with a large number of sets (9-12 sets) and generally very few reps (1-3 reps) at significantly lower intensity often dictated by bar speed of 0.7 to 0.9 m/s (equivalent to an implied load of approximately 50-60% 1RM). Note that when I say \"lower intensity\" I mean lower %1RM, but every effort must be explosive (as fast as possible) are are still maximal intensity in that regard. Additionally, DE is often accompanied by additional features such as external resistance to mimic the force curve (load gets heavier towards peak concentric contraction) through the use of chains or anchored power bands - Another feature of this method is the variability of exercise selection. Under what is known as a conjugate system, exercises are regularly cycled (with some consideration of movement proficiency and experience), so rather than always back squat as the lower body exercise, an athlete may consider: Deadlifts, Front squats, Sumo deadlifts, Box squats, Etc. - Repetition method: after main lifts on both ME and DE days, accessories are done with more conventional loads, ie: 2-4 sets, 6-10 reps. Every 4th week, ME days main movements are done deloaded as a rep method day.   5/3/1 Method - Uses the same fundamentals of weightlifting with an emphasis on technique. - Done starting with light loads and block progression or overload model - 4 sessions per week, each day focusing on one core lift. - Uses elements of periodisation, increasing intensity in an inverse relationship with volume and week 4 is a deload.   Stack 10 - Volume based method - Has significant overlap with hypertrophy. Is used to help break a plataeu. - Is ramp protocol style but reps are capped at 10 - The general process to each exercise would be as follows for whatever exercise you are completing: a. Do a set of 10 reps with an empty (20 kg) bar. b. Add 10% of your 1RM. c. Do 1x10 d. Add 10% of your 1RM. e. Repeat until failure. - Generally this volume would be too excessive to be training multiple lifts on different days, so it is perhaps best employed as a means of overcoming plateaus in progression on a single lift at a time, with other strength training sessions using more traditional maximal strength loading (e.g. 3-6 sets of 1-3 repetitions per set).   ***5.5: Hot topics in the literature*** Velocity Based training - Based on the speed of the bar during the lift. - Not looking at a fixed load   Reps in Reserve (RER) (Auto regulation) - Auto-regulation involves you asking an athlete after the completion of a set "How many more reps do you think you could have done?" The response approximates what %1RM they are lifting - The advantage of auto-regulation is that it allows you to account for your athletes getting stronger between 1RM fitness tests, or to have off days ***6.1: Force, Velocity and power*** Formulas: - Power (J/sec or Watts) = Work/Time = (Force x displacement)/Time - Displacement/Time = Velocity - Power = Force x Velocity   When training power, the goal is to increase force output or velocity of the task Furthermore, when you are trying to decide just how fast the bar needs to move when lifting, or the ideal loading to achieve peak power, there is some indication that \~30% 1RM (range from 30-60% 1RM) will generally achieve peak power (an ideal balance of velocity and force). But this does not mean you cannot benefit from training other strength qualities. Think back to the diagram for VBT. Heavy strength zones other than \"absolute strength\" included \"accelerative strength\" and \"strength speed\", while more speed-based properties include \"starting strength\" and \"speed strength\". That power PEAKS at \~30%. But remember that power is not either on or off. Power is still being used no mater where in the force-velocity curve you are.  Load Power Profile - Traditionally, we say power optimises somewhere between 30-60% 1RM, but this is a pretty big range! Do not think just because you are training with a power-optimising load that you are training power. You must be lifting an optimal load ballistically. Cruising with an optimal load is only lazy training. - The goal of the load-power profile is to identify the optimal load to train peak power.  LPP can also be used to identify athlete more in need of strength or speed training.  - Load-power profiling involves gradually loading a bar heavier and heavier and getting them to do a ballistic movement with each load. The required equipment is something that can measure velocity, such as a GymAware (several thousand dollars) or force plate (many tens of thousands of dollars). While a GymAware or force plate are extremely accurate, they can be beyond the affordability of all but universities, professional clubs, and sports institutes. More affordable force/velocity assessment tools include Flex (infrared) and VMaxPro (accelerometers) that come in at a few hundred dollars, or Metric VBT (camera-based phone app) in the app store. Whilst the accuracy may not be there, they are more cost friendly.     ***6.2: Plyometrics*** - Plyos rely on the elasticity of our muscles, as well as the SCC, in order to rapidly generate force. - A plyo has a rapid strength at the beginning. The simplest example (and first progression) of this would be to jump into the air and stick the landing. On landing, the impact forces the muscles of the legs to rapidly lengthen to absorb the force. This rapid lengthening triggers the SSC to stabilise the landing. - The next progression is to jump from the ground and land on the ground but immediately jump again. This adds difficulty by adding an explosive (concentric) movement to capitalise on the force and speed generated by the SSC. Eg: hurdles, bounding etc. - Further progressions would be something like a depth jump or a depth jump into a counter movement jump   Plyo Phases 1. Eccentric: the lengthening or rapid stretch 2. Amortisation: isometric transition between the eccentric and concentric. 3. Concentric: the shortening   Storage/use of elastic energy - The plyometric effect is wasted (dissipates into heat) as coupling time increases - The plyometric effect is maximised when CON phase follows ECC phase straight away - The plyometric effect is contributes up to 70% of power from a countermovement jump - With training, more energy is stored and subsequently utilised as muscle force increases   Stretch Reflex - Muscle spindles detect magnitude and rate of length change; the greater the impact, the greater the stretch and thus the greater the \"spring\" (i.e., enhanced muscle contraction) - The spindles not only trigger a \"spring\" from the agonists, but a relaxation of antagonists. If you think back to the module on neural adaptations to strength training, we\'ve already discussed the value of reducing co-activation to improve force output.    When it comes to programming plyometric exercises, the quantification of load is a little different to other forms of power training. The optimal volume is still somewhat unresolved, and sometimes measured differently by different coaches. The most common, and suggested metric for plyometric load is the number of contacts per session. You can follow this general indicator for the suggested contacts per session ranges: - **Beginner** - 80 -100 per session - **Intermediate** - 100 -120 per session - **Advanced** - 120 -140\* per session \* By the time an athlete is \"advanced\", training load management becomes an important issue. Perhaps the athlete can handle 140 ground contacts, but in the grander scheme of their training 140 will almost certainly be too mu much.  Despite the inherent benefits of plyometrics, concurrent strength training in addition to SSC training is recommended. This means that when planning a training week, it does not necessarily supersede other resistance training for power development. In terms of frequency, it will depend on the stage of your training cycle as to how often plyometric sessions/components of sessions are employed. Training days in season and pre season will look different.   plyometric movements are useful for training to produce greater power than concentric only movements, as more force is realised during the concentric phase due to briefly stored elastic energy from a rapid transition from the eccentric phase. As an additional benefit, training may increase the elasticity of muscle & tendon complexes for the primary joints used in plyometric movements.   ***6.3: Traditional Gym Training for Power to Compliment Sport Training*** Training heavy and slow - Motor unit recruitment follows the size principle - When you train heavy and slower, 1-5 rep range, you\'re working the more high force, lower velocity portion of the force velocity curve. This helps when performing movements from zero velocity that are more explosive, o maximising motor unit recruitment from nil helps with the efficiency of recruitment and rate of force development. This also aids in overcoming the inertia imposed by body mass. Thus the VBT term, \"accelerative strength\".  - While \"velocity specificity\" is indeed a real thing (e.g. you may have heard that, since heavy weights are moved slowly, training with heavy weights will make you slow) be sure to keep your other high-speed training and the pair of strength training + speed training will make you faster. Getting stronger only makes you slower if it\'s all that you do, but strength training + your training on the field/track/court will make you faster. - From a logistics point of view, you need to be able to exert high force before being able to exert high force *quickly*. This is why we see in \"block periodisation\" that we so a strength block before power: strength plays an important part in power.   Training Explosively - This has numerous approaches - By focusing on the *intention *to move a load as quickly as possible, there is evidence to suggest it enhances the neuromuscular facilitation associated with power output, enhancing the rate of motor unit recruitment and maximising muscular engagement. The intention to move quickly may be independent of actual bar speed, so my 90% 1RM back squat may be moving very slowly, but if my brain is cuing to move like I\'m trying to jump, it may have similar benefits to actual ballistic training. - As mentioned previously, this relates to the size principle, but also accelerated rate-coding (the speed of action potential signalling), which allows for an increase in synchronicity (action potentials reaching the motor unit at the same time). This can be applied effectively with low-to-moderate loads of 30-60% 1RM, but also with high loads \> 80%, as it is an internally driven mental stimulus. Even if the load does not end up being lifted with lightning quickness, as long as the ***intention ***to do so remains, it can still be an effective contributory strategy to improving power output. We call this \"maximal intent training\". - Perhaps another of the most obvious approaches is to employ weightlifting-style lifting. The weightlifting lifts are the Snatch, and the Clean & Jerk. Usually, in the S&C environment, we don\'t train full weightlifting movements, but only the more useful parts of then for us (i.e. the weightlifting derivatives). Pulling a bar from the floor has few sport specific applications, but exploding from an athletic stance does, so rather than train to pull a clean from the floor we may train to pull it from just above the knee (the \"hang\"). Another weightlifting derivative, the \"power clean\", essentially cuts out the full squat position after the catch phase. So if we pull from the knee with a high catch we call it a \"hang power clean\", which puts most of the emphasis on the explosive hip drive from a sport-specific position. - Generally, weightlifting derivatives (i.e. using parts of weightlifting movements like \"hang power cleans\" or \"low snatch pulls\") should use moderate-to-high loads for the optimal training load. But technique is perhaps more important than the loading parameters for weightlifting derivatives. Generally avoid training sets of more than 3 snatches at a time or more than 5 cleans per set; weightlifting can be exhausting work and fatigue during weightlifting leads to lower power output and often a break-down in technique.  - Many S&C coaches believe that it takes at least 6 months for an athlete to get sufficiently confident in the weightlifting skills to overload them, so choose not coach them. This is not necessarily true, Some additional notes on weightlifting derivatives: - Max extension at the hip, knee, and ankle is achieved during the second pull.  This is known as triple extension. - Triple extension is seen in a variety of athletic movements such as jumping and running which is one reason why the snatch is an excellent exercise for athletes to use in their weight lifting program. - Hips had the highest power demands and joint angular velocities. - Plantar flexors contributed to 10% of the barbell's maximum velocity. - The knee bend in the transition phase allowed the body to use the knee extensors' stretch reflexes to develop muscular power.   However, given the technique proficiency required for weightlifting derivatives, it may not always be the most potent training stimulus. Traditional weights and lighter loads are also effective for training power. Completing common compound lifts (think Squats, Bench Press, etc.) with loads in the range of 30-60% 1RM can be appropriate. The major shortfall here is the inherent deceleration of weights towards the end range of many of these movements. To overcome these deceleration issues, accommodating resistance can be added (as was mentioned with the Westside method in the week 5 content) using chains and anchored power bands. Alternatively, 'ballistic' movements can be used where the weight is released at the top of the movement, creating a follow through and minimising the deceleration under load.   Interestingly, depending on what type of exercise you employ, the optimal loading is likely to change even if peak power is the ultimate training objective across all exercises. Take this example from Kawamori & Haff (2004) highlights the need to manipulate load based on several factors including region of the body being trained, multi- versus single-joint exercises and nature of the exercise (weightlifting versus plyometric