We often hear in the industry that one should perform a rep as explosively as possible on each repetition. This methodology has been recommended by authors who write articles for the purposes of both hypertrophy and sport-specific training.
The theory is that by maximizing “explosiveness” one will fully activate the high-threshold motor units (HTMU’s) which will lead to the largest rates of hypertrophy and rate of force development (RFD).
In truth, there’s not much evidence that proves that explosive lifting improves sport performance over controlled lifting. In fact, Bruce-Low and Smith wrote an entire paper on this topic. I highly recommend you check it out so I’ll provide you with a link to the article.
Furthermore, the findings of Hay et al., who measured joint torque in three males while performing biceps curls, also seem to support this view. Hay et al. found that with short duration lifts (< 2 s) very little joint torque was required to move the weight through most of the range of motion (ROM), as after the beginning of the movement the weight continued to move under its own momentum. Therefore, fast movements do not provide as much muscle tension as slow movements through most of the ROM, suggesting that faster repetitions, such as those performed with ‘explosive’ exercises may not produce optimal strength increases through a muscle’s full ROM.
This would apply to hypertrophy as well, various muscles involved in the initial stages of the lift may be stressed very well during explosive movements while other muscles involved at the conclusion of the lift may not be stressed very well.
It has been shown that isometric protocols are "range specific" meaning that they only work really well for a certain range of movement, not the entire movement. From the research above we see that various speeds of repetitions are "range specific" as well.
Finally, EMG data shows that certain exercises fully stress various muscles at different portions of lifts as well. For example, a squat shows more glute activation at the bottom of the movement whereas a hip thrust shows more glute activation at the top of the movement. For this reason, I call the squat a "stretch-position" exercises and a hip thrust a "contracted-position" exercise.
Contrary to popular opinion, the same muscles aren't active in the same proportions throughout a movement, and different portions of muscles get worked through different ranges as well. In Supertraining, Siff explains the popular, yet erroneous view that:
• The same movement is always produced by the same muscles
• The same muscles always produce the same movement
• The same muscles are dominant throughout the full range of movement
• Muscles only act as active tissues
• Muscles only act as movers or stabilizers
• Muscles are the only important tissues which control movement
These misconceptions simply are not true. Some muscles don’t kick in until leverages and length-tension relationships change during a lift and are also impacted by directional load vectors. This is especially true of compound movements and movements involving the hip joint. As a matter of fact, some muscles can have opposing roles throughout a range of motion. This is called the "inversion of muscular action." A prime example is the adductors; they are hip extensors when the hips are flexed and hip flexors when the hips are extended.
So if you want to maximize hypertrophy and/or the transfer of strength training to sport, you must consider which "range" the muscles are being stressed per each exercise and type of repetition. In sport-specific training, it's not just about "the movements;" it's about muscles, joint angles, load vectors, energy systems, transfer through other areas of the body, etc.
In sports you power through movements such as a sprint stride or jump so you need to be strong and powerful in all ranges.
There are benefits and drawbacks to each type of repetition and exercise. I’ll list just some of the pros and cons to a variety of common types of repetitions:
Benefits of explosive lifting: increased strength in stretched position, best method for starting strength, best method for rate of force development, possibly more tissue damage due to increased stress in stretched position – good for hypertrophy in muscles initiating the movement
Drawbacks of explosive lifting: deceleration up top in contracted position, not so good for finishing strength, not good at producing constant tension which may be critical for hypertrophy
Benefits of controlled lifting: increased strength throughout entire range of motion, no “assistance” from high momentum which requires considerable muscular tension at all ranges, more “constant-tension” which would lead to occlusion and hypoxia – great for hypertrophy
Drawbacks of controlled lifting: slow movement speed, submaximal acceleration
Benefits of accommodating resistance (bands and chains): acceleration, good method for finishing strength
Drawbacks of accommodating resistance (bands and chains): submaximal stress in stretched position compared to straight weight, less stable, doesn’t truly match the “strength curve”
Benefits of weight releasers: accentuated eccentrics
Drawbacks of weight releasers: only works for one repetition
Benefits of isometrics: can improve any specific area of a particular lift
Drawbacks of isometrics: range specific; doesn’t transfer well to other ranges, may interfere with elasticity and power production
Benefits of eccentrics: great for agility, deceleration, and hypertrophy
Drawbacks of eccentrics: extreme soreness, doesn’t always transfer perfectly to concentric strength, sometimes requires spotter
Benefits of ballistics: great for rate of force development and reactivity/elasticity
Drawbacks of ballistics: not good for hypertrophy or max strength
Benefits of concentric-only exercises (ex: sled pushes): reduced soreness
Drawbacks of concentric-only exercises (ex: sled pushes): no eccentric phase, suboptimal for hypertrophy
Benefits of stretched-position exercises: improved starting power
Benefits of contracted-position exercises: improved finishing power
Benefits of eccentric quasi-isometrics: great for simultaneous mobility and stability, great for starting strength
Drawbacks of eccentric quasi-isometrics: not very good for hypertrophy or max strength
Benefits of partials: good for hypertrophy, uniquely stimulates the CNS and connective tissue in a manner that lighter full-range movements can’t
Drawbacks of partials: range-specific; doesn’t transfer well to other regions of the movement
This is why I believe that a combination of exercises and rep speeds should be performed for both hypertrophy and athleticism seeking lifters. One simply cannot get optimal development from only one method. Certain exercises lend themselves better to explosive reps while certain movements lend themselves better to controlled reps. One should have variety in one’s training in regards to both exercise selection as well as types of repetitions in order to maximally strengthen all ranges of motion if one’s goal is to develop the biggest muscles possible or the most powerful muscles possible.
Bruce-Low, S. et al. “Explosive Exercises in Sport Training: A Critical Review.” J Exer Phys Online. 10(1) (Feb 2007): 21-33.
Hay JG, Andrews JG, Vaughan CL. “Effects of lifting rate on elbow torques exerted during arm curl exercises.” Med Sci Sports Exerc 1983;15:63-71.
Siff, Mel. Supertraining. 5th Ed. Supertraining Institute, 2003: 194.