If you were unfortunate enough to have missed it, or not had chance to read it yet, the excellent Strength and Conditioning Research by Chris Beardsley and Bret Contreras recently posted a mammoth 50,000 word super review on hypertrophy fear not.
The review was centred around the analysis of long term trials (unless you are a genetic freak or “enhanced “hypertrophy is very much a long term adaptation) that have explored the effects of specific, individual training program variables. These specific training variables are;
- Relative Load
- Muscular Failure
- Rest Periods
- Range of Motion (ROM)
- Bar speed
- Muscle Action (Variable load)
Each section of the research was given a rating for research quality, a summation of the long term findings for hypertrophy and the confidence the reviewers had in said findings.
Within the research Chris and Bret made a very pleasing distinction between studies on untrained and trained subject. In the beginning of your training life almost anything resistance training related (within reason) will result in improved strength and hypertrophy. Therefore when trying to summarise the findings of trials on specific training variables the inclusion of both trained and untrained subjects can often muddys the waters as what is best or “optimal” for an untrained subject may well differ to what is applicable to a trained subject.
Over the coming weeks (potentially months) I will be writing a series of shorter articles that will be an attempt to break this beast down into some more manageable (and actionable) chunks.
It should be noted that due to the exceptional calibre of SBS readers (pat yourself on the back for having such discerning taste) the research reviewed will be that on the trained subjects only. If you are interested in the articles on the untrained subjects then head over to Shreducation.
Week one kicks off with a look at the research into relative load (percentage on 1RM).
Relative load (Percentage of 1RM).
To explore whether training with heavy loads (<15RM ) is more effective than training with lighter loads (>15RM) for hypertrophy.
Understanding Relative Strength
We as humans do not all have the same levels of strength (after all there may be a few Kg difference in what I and Klokov front squat!). Therefore training programs often use percentages of 1RM when prescribing weights (relative strength) as apposed to absolute loads.
Conceptual Basis for Hypertrophy
Throughout this series it is important to try to understand a rudimental conceptual basis for hypertrophy (I say try as it hurt my head reading it). The review goes into mind-boggling detail on the mechanisms of hypertrophy ,many of which are still up for debate. While many of you readers may be aware of Dr Brad Schoenfeld’s (2010 ) conceptual framework for hypertrophy in regards to mechanical loading, exercise-induced metabolic stress and muscle damage, the authors used the conceptual categorisation presented by Pearson and Hussain (2014). This categorisation, used originally in the context of blood flow restriction training, identifies two primary stimuli in the form of mechanical loading and exercise-induced metabolic stress. From these primary stimuli a number of secondary mechanisms such as muscular damage, systemic and localised hormones , cell swelling etc result. I will not even attempt to explain them all here as to save my dignity and your reading time. If you want to know more read the paper, if not just keep in mind the primary stimuli for hypertrophy are mechanical loading and metabolic stress. Got it? Good.
Relative Load and Mechanical Loading (Conceptual)
Higher relative loads may be expected to induce greater mechanical loading when compared to lower relative loads in two ways.
- Greater relative loads are heavier (doesn’t require much explanation)
- Higher relative loads often result in lower bar speed and longer repetitions times (when maximal bar speeds are used)
Higher relative loads therefore could be expected to activate more motor units (due to the load) for a longer period of time (due to the repetition speed) compared to lower relative loads. However, it is hypothesised this hypertrophic response to mechanical loading has both an upper and lower thresholds. A lower threshold where the relative load is too low to induce any meaningful stimulus for hypertrophy and an upper threshold in which no further hypertrophy occurs in response to increasing relative load. This upper limit may well be due to the trade off between increasing relative load and the total number of repetitions one is able to perform at said load thus increasing the mechanical load but concomitantly lowering the period of time the motor units are activated for.
Relative Load and Metabolic Stress (Conceptual)
Muscular contractions above a certain threshold of maximum voluntary isometric contraction prevent venous return. Preventing blood flow back to the heart results in the build up of metabolites within the muscle , inducing metabolic stress. Longer duration sets (with lower or moderate relative loads) would then be expected to promote greater levels of metabolic stress and thus hypertrophy (as long as all other factors remained constant).
Higher relative loads might be more effective than lower relative loads for hypertrophy due to the greater magnitude and possible longer duration of tensile force within the muscle (if bar speeds are maximal). However when taking metabolic stress into consideration moderate relative loads may be more effective at inducing metabolic stress when compared to heavier relative loads.
Molecular Signalling for Hypertrophy
Results comparing the molecular signalling responses between heavy and light relative loads are conflicting. Of the 10 studies listed, 5 studies indicate signalling responses are greater with heavier relative loads whist the remaining studies show no effect or support lower relative loads. These conflicting results may be due to some of the flaws in the research and their design.
Problems with the research
- Firstly a lack of trained subjects within the studies. Long term studies that include trained subjects will always be hard to come by as these subjects often dislike their training being messed with for extended periods of time (would you?).
- Un-equated volume. Individuals perform different number of repetitions with the same percentage of 1RM. Therefore certain individuals may perform a greater volume of work (total repetitions) than others.
When it comes to hypertrophy the current research appears to support the recommendation of training across a range of relative loads. Higher relative loads generally inducing greater mechanical loading and more moderate relative loads promoting greater metabolic stress. Whilst these findings may be far from spectacular they provide a fascinating insight into the conceptual mechanisms of muscular hypertrophy.
Next week we will tackle one of the hottest topics when it comes to hypertrophy and that is volume.