Using Intensity to Increase Strength, Power, and Endurance
Training intensity. Should it be defined relative to the level of physical effort expended or the numbers in the antiquated system of the one-repetition maximum (1RM)?
Let’s begin with Merriam-Webster's definitions of the word intensity:
- The quality or state of being intense. Especially, the extreme degree of strength, force, energy, or feeling.
The magnitude of a quantity - as force or energy - per unit (as of area, charge, mass, or time).
Implications of the Definition of Intensity
Two thoughts can be gleaned from the above definitions. For one, it suggests intensity relates to effort exuded to perform a task. This could mean two things regarding strength training:
- Extreme effort put forth in an exercise set independent of the amount of resistance used and the number of repetitions (reps) desired.
- Whether low reps/heavy resistance or high reps/light (relative) resistance is required, intensity would be defined by the effort required to complete the specific task.
Either way, going all-out would mean 100% intensity was procured. But regarding force, it can be implied that the higher the force output required the higher the intensity. Likewise, the lower force output required the lower the intensity.
Secondly, Merriam-Webster’s definition suggests a quantity or amount. A greater amount equals high intensity and a lesser amount equals lower intensity.
In most strength training programs, "X" amount of resistance is lifted for "Y" number of repetitions. Therefore, lifting 93% of a 1RM for two reps would be highly intense due to the magnitude of the resistance and greater immediate force required. On the other hand, lifting 65% of a 1RM for two reps would be less intense. That is pure common sense, but who only lifts 65% of a 1RM for two reps?
Resistance Training Should Be Demanding
To grow muscle, get stronger, improve power output, or shed fat, no one can argue that resistance training should not be demanding. For the love of Henry “Milo” Steinborn who proved years ago that it should be challenging, take a look at these undisputable facts:
- High, medium, and low intensity efforts - and using various percentages of a 1RM for a specific number or repetitions - are all subjective relative to specific outcomes.
- Too many combinations of load and effort expended to move resistance in the endeavor to only get stronger, only improve power, or only enhance endurance makes it impractical to categorize workout loads and specific reps as strength-only, power-only, or endurance-only.
So, where do you draw the line between the three? If you understand the science behind all this then you know what I am talking about. If not, it can actually be embarrassing when you finally understand reality. If you're still confused, go read the proven research on this topic.
"To grow muscle, get stronger, improve power output, or shed fat, no one can argue that resistance training should not be demanding."
The Role of Volitional Muscle Fatigue
Pushing or pulling against a relatively heavy resistance with maximum effort (dynamic reps or a static contraction) to the point of volitional muscle fatigue creates an overload on muscle tissue. Do this progressively over time and you get stronger and gain muscular endurance.
Likewise, pushing or pulling against a relatively light resistance (such as 60% of a 1RM which is 60% greater than no resistance at all), and doing so with maximum effort (again, using dynamic reps or a static contraction) to the point of volitional muscle fatigue also creates an overload on muscle tissue. Do this progressively over time and again you get stronger and improve muscular endurance.
Based on that, the greater your intensity of effort, the greater your potential to gain strength and muscular endurance, independent of load amount. The greater the load, the fewer number of reps attainable. The lesser the load, the greater number of reps possible provided the set is performed to the point of volitional muscle fatigue. Going all-out makes it objective.
Intensity Relative to a Percentage of One Rep Max
Look at this issue from the traditional definition of intensity relative to a percentage of a 1RM used in most set/repetition scripts:
Training with 90-100 % of a 1RM would be considered high intensity. Doing this would mean many muscle fibers are recruited to complete the task. In reality, though, a minimal number of fibers are actually overloaded in the process. The higher threshold and faster-to-fatigue muscle fibers are recruited to complete the task, but there are a ton of lower threshold and slower-to-fatigue fibers that are not overloaded.
Training with 60-70% of a 1RM would be considered low intensity in accordance to the traditional percentage system verbiage. In this scenario, only the lower threshold and slower to fatigue fibers would theoretically be recruited. At the outset of the set, this is true. But if the exercise set is taken to the point of muscle fatigue via maximum reps, then a large percentage of available muscle fibers will be recruited and overloaded, albeit with the use of a relatively lighter resistance (see Henneman's Principle).
Training between 75-85% would be considered medium (or medium-high?) intensity.This is where the reality of the percentage system is exposed. Where do you draw the line between the subjective nature of intensity levels? We discovered a cure for polio in 1952, Jack Kilby invented the first microchip in 1958, we put a man on the moon in 1969, and Coke Zero was first marketed in 2005. Yet, we cannot come to a consensus on training intensity as our society continues to erode toward obesity and poor health.
Training with 95% of a 1RM would be considered high intensity. Yes, it would be intense due to the maximal effort required in the short (time-wise) exertion. Absolutely difficult, few reps performed, and a large number of muscle fibers are recruited, but fewer relative muscle fibers are actually overloaded.
If maximum intensity was solely based on the percentage system to accrue optimal development, then should not all sets be performed with 100% of a 1RM? After all, that is the epitome of the percentage of 1RM training. Perform set after set with the heaviest load possible and, of course, you would elicit an adaptation. But is it prudent to do that?
Less Load Can Mean Better Muscle Fiber Recruitment
What would occur if you lowered the intensity to 90%, 82%, 75%, or 60% of a 1RM? Would you then be selling out to a lesser potential gains? Based on convoluted modern thought, these resistances would be ineffective for developing specific qualities.
Take it down to the aforementioned 90% of a 1RM - still considered high intensity within the confines of conventional wisdom. With 90% of a 1RM, more reps are possible as compared to 100% of a 1RM. With 90%, you get four reps as opposed to one. In this case, more time is spent recruiting and fatiguing muscle tissue. There is an upside to sub-100% 1RM loads - more time under tension and a greater potential to recruit and overload a greater number of working muscle fibers.
"Believe it or not, lesser 1RM loads have the potential to recruit and overload a greater relative number of muscle fibers as compared to the end of the continuum, the 1RM for one rep."
Take it down even further to the low intensity of 65% of a 1RM. Depending upon the exercise and rep cadence, performing a maximum number of reps with 65% could create fatigue at fifteen, nineteen, 24, or whatever number of reps. Believe it or not, lesser 1RM loads have the potential to recruit and overload a greater relative number of muscle fibers as compared to the end of the continuum, the 1RM for one rep.
Think about it. In accordance to how humans recruit muscle based on the task at hand, working with 65% of a 1RM - which is 65% greater than no resistance at all - a significant number of muscle fibers are initially recruited (again, 65% vs. o% of a 1RM). If the resistance is lifted for a maximum number of reps as opposed to one, a large pool of fibers are recruited and stressed. As work progresses, muscle fibers fatigue, more are recruited to complete the task, and there is a greater time under tension. This guarantees more fibers are used across the spectrum of the load/recruitment schematics.
- Training intensity should be defined as the effort put forth to complete a set, independent of the load (% of a 1RM) used.
- Training load should be defined as the amount of resistance used in a set, independent of the effort expended.
- Going all-out with a heavy load (88% of a 1RM) and completing five reps would be high intensity of effort. Only performing one rep with 88% would not be high intensity.
- Going all-out with a lighter load (65% of a 1RM) and completing seventeen reps to volitional muscle fatigue would be high intensity. Only performing eight reps with 65% would not be high intensity.
- Many set/rep/load protocols work provided you work hard. Regardless of the load used, going all-out is measurable and maximally recruits muscle fibers and improves your pursuit of increasing strength, power, and muscle endurance.
1. Bass, C. "Forget Heavy, Think EFfort. Muscle Fiber Activation and Rep Range." Ripped Enterprises. 2009.
2. Carpinelli, R. "The Size Principle and a Critical Analysis of the Unsubstantialted Heavier-Is-Better Recommendation for Resistance Training." J Exerc Sci Fit. Vol 6, No 2, 67–86. 2008
Photos courtesy of CrossFit Empirical.