Greek “excess” + “nourishment”
Hypertrophy (Increase In Muscle Size)
Adding to changes in mass & volume (e.g., fluid and protein).
Two factors contribute to hypertrophy: SARCOPLASMIC (non-contractile elements) hypertrophy, which focuses more on increased muscle glycogen storage, in other words, refers to the increase in volume of fluid.
MYOFIBRILLAR (contractile elements) hypertrophy, which focuses more on increased myofibril size.
When myofibrils become thicker, there is more surface area connecting individual myofibrils to one another. Strength is based on a muscle’s ability to generate tension, as the surface tension between individual fibers increases, the net result is greater force output from the entire muscle. As a muscle experiences myofibrillar hypertrophy, it becomes thicker and denser, not necessarily larger.
Performing a high volume of reps to fatigue produces the response of sarcoplasmic hypertrophy, an increase in size in the fluid-containing sarcoplasm around muscle cells, but not in the individual muscle fibers themselves. This is how a muscle can get larger without necessarily becoming stronger, it is simply storing more fluid which increases the total volume of the muscle cells.
Claims
Doing exclusively heavy work for low reps, which always leaves considerable cellular energy reserves.
Several studies have discovered strong connections between muscle size and strength or performance.
r values
- 0 – 0.1: No relationship – these variables are not related
- 0.1 – 0.3: Weak relationship – AKA, nothing to write home about
- 0.3 – 0.5: Moderate relationship – now this is kind of interesting
- 0.5 – 1.0: Large relationship – now this is VERY fascinating
- A study found a correlation of r = 0.866 between pectoral muscle size and bench press 1RM.
- A study found a correlation of r = 0.564 between muscle volume and peak torque of the biceps. Biceps cross-sectional area (CSA) was also related to maximum force to the tune of r = 0.637.
- The study found a correlation of r= 0.69 between hamstrings muscle volume and hamstrings peak torque. According to the findings, the size of the hamstrings accounts for about 48% of hamstring strength.
But how much of the variation in variable B (STRENGTH GAIN) can be accounted for by changes in variable A (MUSCLE GAIN)?
Muscle size and strength are often assumed to be linear in the literature (a larger muscle should be stronger).
But, This beautiful line is worth remembering.
“Correlation is not causation” means that just because two things correlate does not necessarily mean that one causes the other. … Correlations between two things can be caused by a third factor that affects both of them.
The study found a correlation of a pre-training correlation of r = 0.787 between biceps volume and biceps curl 1RM.
Is a larger muscle a stronger muscle? That is the ultimate question.
A 2017 12 Weeks, 3/week RCT Study (#28 Healthy Young Men#leg Extension# 4 Sets# 10 Repetition#isolation Exercises # No Rm & Rest Period Between Sets Mentioned)
The researchers observed a group of men performing leg extension exercise and measured muscle activation and muscle size, attempting to link these changes to the gain in quadriceps strength.
The change in quadriceps size showed an r = 0.461 correlation with strength improvements, but the change in muscle activation had an r = 0.576 correlation with strength gains. Changes in muscle size contributed to 18.7% of strength gains, whereas changes in activation contributed to 30.6% of the strength gains.(PMID: 28239775)
NOTE: The subjects had not done lower body Resistance Training in over 18 months.
A 2014 12 Weeks, Study (#33 Healthy Untrained Young Men#3 Session/week Alternate Days# Bilateral Preacher Curls On Machine # D/b Unilateral Preacher Curls# 2 Sets For Week 1–2, 3 Sets (Unilateral) And 2 Sets (Bilateral) For Week 3–4, 3 Sets Of Both Exercises For Week 5–12 # 8–10 Repetition# 80% 1-rm # #2-min Rest Between Sets)
A similar research using biceps training aimed to describe the link between muscle growth and activation and strength improvements by measuring muscle size and activation.
The association between muscle growth and strength (r = 0.527) was shown to be highly correlated, however the relationship between changes in muscle activation and strength (r = 0.187) was not.
According to the results, muscle growth accounted for 27.7% of the biceps strength improvements, whereas EMG alterations (muscle activation) only accounted for 3.5% of the strength gains.(PMID: 24610245)
NOTE:The study is a little older and used less advanced muscle size measurements or didn’t use much weight during training, resulting in muscle growth but not significant strength gains.
In 2019 Study. Some researchers have argued that there is no association between muscle size and strength due to a lack of data on the subject. The authors point to a lack of direct studies studying different degrees of development and their relationship to strength improvements as a reason for their conclusion.(PMID: 31020548)
However, there have been other studies in which a subject group grew more muscle and strength than its competitors.(PMID:12436270)(PMID:7095924)(PMID: 26272733)(PMID:16988909)
Strength is a skill, and exercising with heavier weights promotes strength development more effectively than training with lighter weights.(PMID: 12436270)
WHY? Changes in biceps activation did not correspond with strength improvements, although biceps hypertrophy did. Quadriceps growth and activation, on the other hand, were both associated to quad strength. In other words
Biceps Quadriceps
Muscle Activation ≠ strength Muscle Activation = strength
Muscle Hypertrophy = strength Muscle Hypertrophy = strength
HYPOTHESIS
Individual adaptations might be based on a muscle’s fundamental characteristics: voluntary activation (activation by choice). Smaller muscles can be intentionally stimulated to a greater extent than larger muscles – this is a general, not a rule & the primary muscles of the upper body are generally smaller than those of the lower body. In short, the biceps can voluntarily achieve at least 95% of their maximal involuntary contraction, whereas the quads are closer to 85% (PMID: 11870692). Other research has also found that squeezing the biceps and maximally engaging the biceps muscle with no load had similar results as subjects who performed Biceps curls with load (PMID: 27329807)
Well, the Hypothesis is that muscles with lower voluntary activation percentages, on the other hand, may be more dependent on neuromuscular adaptations than hypertrophy for strength improvements. Muscles with higher voluntary activation percentages, on the other hand, may be more dependent on growth for strength improvements since muscle activation is already near maximum.
Olympic weightlifters, powerlifters, and bodybuilders were studied for their thigh muscle area and related to squat 1RM in one fascinating master’s thesis. Although all three groups had equal thigh muscle areas, powerlifters and Olympic lifters were able to squat much higher than bodybuilders. The r =0.20 link between thigh muscle area and squat 1RM (weak relationship – nothing to write home about)
A 2016 8 Weeks, randomize Study (#nineteen Resistance-trained Men #3 Days/week# (Heavy) 2-4 Rep/set, (Moderate Hypertrophy-type) 8-12 Rep/ Set # 3 Sets# Flat Barbell Press# Barbell Military Press# Wide Grip Lat Pulldown# Seated Cable Row# Barbell Back Squat# Machine Leg Press# Machine Leg Extension).
All individuals gained equal amounts of muscle thickness, however the heavy group’s squat 1RM increased much more than the moderate group’s (30% vs 16.8 %). Although the heavy group gained visibly more bench press strength than the moderate group (14.4% VS 10.5%, the difference was not statistically significant, demanding more investigation.
When it comes to strength, this study backs up the hypothesis that lower body muscles rely more on neuromuscular increases, whereas upper body muscles rely more on size growth.(PMID: 27928218)
A 2015 8 Weeks, Randomize Study,“(#33 Resistance-trained Men (5.7- 2.2 Years)#4 Days/week # (Heavy) 3-5 Rep 4 Sets With 90% 1rm,3-min Rest/ Set, (Moderate Hypertrophy-type) 8-12 Rep 4 Sets With 70% 1rm,1-min Rest/ Set #dexa # Muscle CSA # Thickness Of The Vastus Lateralis (Vl), Rectus Femoris (Rf), Pectoralis Major, And Triceps Brachii Muscles # Ultrasound Images # 1rm Strength In The Back Squat And Bench Press # Blood Samples Were Collected Serum Testosterone, Gh, Igf1, Cortisol, And Insulin Concentrations)
The heavy group not only increased their bench press (13.7% vs. 6.1 %), but they also gained more lean mass in their arms (5.2% vs. 2.2% increase), although both the heavy and high volume squat groups increased their hypertrophy and strength.
This supports the idea that upper body muscles rely on growth for strength, as the group that gained the most size also gained the most strength. This does, however, cast doubt on the assumption that lower body muscles aren’t as reliant on size for strength.
Area under the curve analysis showed larger GH and cortisol responses for HYPERTROPHY-TYPE TRAINING (8-12 REP) at Week 3 and cortisol alone at Week 10 as compared to HEAVY TRAINING (3-5 REP).
The GH and cortisol responses were lower for HYPERTROPHY-TYPE TRAINING (8-12 REP) at Week 10, compared to Week 3, whereas the IGF1 response was lower for HEAVY TRAINING (3-5 REP).
During Week 3,Immediately post exercise, TESTOSTERONE levels in both groups were much higher than baseline, but by 30 minutes post exercise, they had returned to resting levels and by 60 minutes post exercise, they had decreased significantly below baseline.
During Week 10, TESTOSTERONE levels remained similar to baseline at the time of exercise and at 30 minutes post exercise, but dropped considerably below baseline at 60 minutes post exercise.(PMID: 26272733)
NOTE: Keep in mind that strength is a skill, and heavy training is more specialized to a 1RM test, which might influence the findings of this research.
DEBATE
Does increase muscle activation result in increased strength gains?
OR
Does an increase in muscle size result in an increase in strength? Because lifting heavy weights causes more muscle activation, whereas lifting light weights with muscle failure causes similar muscle activation. Can both training techniques lead to similar strength gains?
OR
Is Muscle Hypertrophy a by-product of Heavy Weight Lifting (Strength) and Nutrition?
- According to 1968 research, people with smaller muscle cross-sectional areas had less arm strength than those with bigger muscle cross-sectional areas. (PMID: 5700894)
- The remaining question is whether the increase in muscle size caused by resistance training contributes to increased muscular strength? The current theory for explaining muscular strength gains indicates that brain pathways
- (neural pathways or neuromuscular adaptations) have an early role, followed by greater contributions from muscle hypertrophy.
- Brooks and Fahey proposed in 1985 that “muscles are strengthened by growing their size and by raising the recruitment and firing rates of their motor units.” It appears that both of these mechanisms are engaged in the adaptive response to resistance exercise.
- Ikai and Fukunaga produced early evidence that muscular hypertrophy may be connected to changes in maximal strength. In 1970, people who trained one arm and relaxed the other arm acquired strength in both arms but only size in the training arm. According to the authors, the two key processes contributing to strength training improvements in strength are increases in muscle cross-sectional area and nerve discharge. (PMID: 5425330)
- Moritani and deVries’ 8-week research is the initial work that most textbooks reference as evidence for the time course of increases in muscular strength. Subjects exercised out one arm (Biceps curl) while relaxing the other. The results of focus were changes in EMG amplitude and arm circumference. The authors interpreted a decrease in EMG amplitude compared to absolute force measurements as an indication of growth. It is worth noting that muscular development was not really measured. There was an improvement in strength after 2 weeks of training, but there was no decrease in EMG amplitude relative to absolute force, according to the authors. The scientists came to the conclusion that the lack of shift showed that the instant rise in strength was neurological in nature. Following 8 weeks of training, both arms experienced an improvement in strength which is also called “CROSS-EDUCATION EFFECT” or “CROSS-OVER EFFECT” or “MIRROR TRAINING”,, but only the exercising arm had a decrease in EMG measurement. According to the study’s findings, “after the first 3–5 weeks, muscular growth becomes the main component of strength increase.”(PMID: 453338)
and that high-load training also leads to greater skills training for dynamic strength testing.PMID: 28834797
- Strength is a multidimensional skill (can be measured in multiple ways, e.g., isometric, dynamic, voluntary, involuntary) that can be defined as the ability to generate force against an external resistance.(1,2)
- More sarcomeres in a myofibril through training-induced hypertrophy (e.g., sarcomerogenesis resulting in more sarcomeres in parallel) theoretically increases a myofibril’s force generating capability.PMID: 29978560
- It is unknown why covariance (In probability theory and statistics, covariance is a measure of the joint variability of two random variables. If the greater values of one variable mainly correspond with the greater values of the other variable, and the same holds for the lesser values, the covariance is positive. There exists between strength and hypertrophy measurement/biological variability, and the authors have not provided evidence to support this fundamental notion.
As a result, myofibrillar hypertrophy should increase strength directly.
According to numerous research, the claimed gap between hypertrophy and strength might be related to
1) Hypertrophy is not caused by myofibrils.
2) Myofibrillar development without additional changes to other important tissues or the muscle fibre itself necessary to express the enhanced capacity.
3) Before the contribution of hypertrophy can be indicated, strength must be measured. The link between hypertrophy and strength is clear, but the methods used to identify it have frequently missed the opportunity. Hypertrophy is not caused by myofibrils.PMID: 25309456
A recent meta-analysis discovered that high-load training caused greater improvements in dynamic strength, while finding no significant differences between high-load and low-load training in hypertrophy and isometric strength gains. This indicates that hypertrophy improves the muscle’s overall capacity to create force independent of the loading zone, In a training research, one mechanism might rise while another declines, making it impossible to determine the contribution of a single mechanism. The question may not be solved by a single experiment, but rather by a series of trials combined with theory.
Finally, the influence of non-training stimuli on hypertrophy and strength cannot be underestimated. Without any RT stimulus, Bhasin et al. discovered that supra physiological dosages of testosterone (600 mg/week) promoted both hypertrophy (15.7% increase in thigh muscle volume) and strength improvements (17.7% increase in leg press strength). The lack of a training stimulus and the similarity between hypertrophy and strength improvements imply that muscle hypertrophy was the driving force behind the strength gains. Given these considerations, it becomes clear that hypertrophy may be regarded as a contributing factor of strength gains.PMID: 11701431
- Schneider proposed in 1939 that “casual observation is adequate to indicate that the muscles do not make a similar growth in size.”
- Morehouse and Miller wrote in 1963 and 1976, “It has not been proven that hypertrophy is always a great response.”
- Despite multiple research showing that muscle hypertrophy occurs along with increases in strength(PMID: 5425330)(PMID: 409100)(PMID: 22518835), this alone is insufficient to educate us on the role of muscle growth for increasing strength. When examining the classic studies used to support this “neural first, hypertrophy later” narrative, one thing to explore is what would have happened if both arms were trained, but one was designed to decrease growth?
- (PMID: 27875635)(PMID: 28463902)We’ve been experimenting with a model that allows us to adjust the strength without changing muscle growth. Despite its limitations, this model may provide some insight into how important a change in muscle size is for a change in muscle strength.
Muscle Growth Isn’t Necessary, Sufficient, or Contributory to Muscle Strength Increase?
Exercise-induced muscle hypertrophy may not be enough to explain the increases in strength. Since more researchers have begun to investigate alternatives to high load resistance training for increasing muscle size, studies have supported this theory are beginning to appear in the research. For example, body weight exercise studies have found gains in muscle hypertrophy but not necessarily changes in muscular strength [PMID: 29446524, PMID: 29471132]. This is supported by two further researches using extremely low load resistance exercise, in which muscle hypertrophy appeared to increase similarly but strength in the action under trained did not [PMID: 21385216, PMID: 30386254,PMID: 28834797]. The strength difference may typically be reduced by having the low-load resistance training group perform higher lifts on an occasional basis.PMID: 27174923.
Muscular hypertrophy is not required for muscle strength to increase. For example, if one arm is exercised while the other stays untrained, strength in both arms will grow.(PMID: 17043329) The “CROSS-OVER EFFECT” is assumed to be mostly related to brain adaptations since muscle growth does not occur to a significant extent in the untrained limb(PMID: 8045847). Individuals may also enhance their strength by visualizing(MENTAL (MOTOR) IMAGERY TRAINING) themselves performing the movement, which is thought to be the result of brain adaptations(PMID: 24133427). Together, this provides evidence that muscle hypertrophy is not required for increased strength.
According to the hypothesis, while both muscle growth and strength can improve after exercise, these adaptations are distinct and unrelated. The argument that muscle growth adds to strength appears to be based mostly on two points:
(1) the baseline link between muscle size and strength, and
(2) the addition of contractile protein should result in an increase in strength.
The first statement is valid, but a baseline correlation does not always correlate to what happens in reaction to exercise.
When investigating correlations on change scores, these studies are carried out on groups aimed to enhance both muscle growth and strength, and they also appear to be primarily relating the error/random biological variability,
with the error/random biological variability in muscle strength(linked to measurement inaccuracy and low inter-individual variability), with muscle size.[PMID: 28819744]
The second argument appears straightforward, yet there is a surprising lack of evidence demonstrating that increased muscle size correlates to increased voluntary strength. Currently, the mechanistic impact of muscle growth is mostly decided by whether a change in muscle size was found compared to nothing [PMID: 11454977,PMID: 8800357], a non-exercise control group [PMID: 4091001, PMID: 1435173], or another group that may have also experienced increases in muscle size [PMID: 23278841,PMID: 16871002].
If research shows increased muscle size and strength, the conclusion is usually that muscle growth had a role. When people improve their strength but not their muscle size, the logical conclusion is that the process is not growth but rather neural.
Muscle growth is similar, but strength is not; this might indicate that muscle growth is not a mechanism for strength gain.When all data is examined, there is strong evidence that muscle growth is not required for an increase in strength and some evidence that muscle growth is not sufficient for an increase in strength.
The study is designed in such a way that one group is assigned to improve both muscle size and strength, while the other group is assigned to increase only strength by regular exercise with high loads. The results were successful in producing variations in muscle development (of varying magnitudes), but the strength adaptation was very similar [PMID: 27875635,PMID: 28463902].
There are limitations to these studies.
There was no comparison to a non-exercise control group that was time-matched.
Muscle hypertrophy was mostly estimated from B-mode ultrasound, therefore the results may differ with different examinations. (Changes in B-mode ultrasound and magnetic resonance imaging appear to follow a similar pattern.)
The study lasted 8 weeks.
Because the study was done on untrained people, the findings may differ over time (months/years) and with a larger sample of resistance-trained men and women. However, the time and population employed by the research usually used as evidence for the hypothesis of “neural first, followed by hypertrophy” are the same.
Finally, even though the exercise was done at a high percentage of their maximal strength, the load was not matched between conditions. Literature on detraining
A group of young people was trained for 16 weeks and then detrained for 6 months. It was found that all the muscular hypertrophy that happened during training was lost after detraining, but that the strength obtained during training was mostly maintained [PMID: 21131862] (use it or lose it Principle).
The study does not necessarily support muscle hypertrophy as a mechanism, but it is useful for considering alternative hypotheses for the mechanisms of strength gain (given that a loss of exercise-induced growth did not appear to impact strength),
we hypothesize that changes in muscle size and strength are potentially separate and unrelated phenomena; that is, increasing one does not cause an increase in the other.
What if it isn’t muscle growth?
Strength increases are normally proportional to the specificity of the skill and the specificity of the load. People who train with a heavier load tend to be better at lifting heavier loads than those who exercise with a lighter load.[PMID: 28834797]
Some hypothesize that these variations in strength are the result of
- Nervous system changes in the primary motor cortex[ PMID: 16891123].
- Spinal cord [PMID: 12015341].
- Changes in the alpha motor neuron [rat study, PMID: 28596267].
- Changes in the calcium release pattern [PMID:9716403] .
- The key components of the stimulation contraction coupling process have changed. (PMID:1761971) .
- Changes at the fiber level changes at the fiber level that occur without influencing of changes in muscle size.[PMID: 30357517].
Final Words
There is a causal claim regarding the contribution of one variable to another, that is, a change in one contributes to a change in the other, but it is a contributory-causal link with no experimental proof.
This claim must be tested in trials in which muscle hypertrophy is changed across groups to test the impact of such manipulation on changes in strength.
- Are the following evidence sufficient to demonstrate that hypertrophy is a result of strength training or that hypertrophy is influenced by strength training? Included is research on the baseline link between muscle cross-sectional area/mass and strength, muscle size and strength change scores from trials aimed to increase both, changes in skin fold thickness and muscular strength.
Individuals who followed the traditional training program (8-12RM) improved muscle growth and strength, whereas the group that simply did repeat 1-RM testing increased muscular strength to a similar level despite not growing muscle size.
As a result, the resulting gains in muscular strength cannot be the result of muscle size increases.(PMID:28463902)
Compared to between-subject analysis, analyses explain a substantially higher percentage of variance in strength growth.PMID: 28276188
Methods matter: the relationship between strength and hypertrophy depends on methods of measurement and analysis.PMID: 29967737
Strength increases in the first 4–6 weeks, with little to no noticeable hypertrophy.PMID: 453338 PMID: 17053104
Muscle hypertrophy and strength improvements have minimal relationships, with hypertrophy accounting for as little as 2–28 percent of the variation in strength development.PMID: 26767377 PMID: 30387185 PMID: 24610245
Homogenous groups of trained people (> 1 year RT), showing that hypertrophy accounts for a higher share of the variation in strength development as training status increases.PMID: 30387185 PMID: 8800357
Longer-term research on trained individuals suggests that hypertrophy, as measured by increases in body mass and fibre cross-sectional area, accounts for 65 percent of the variance in strength growth.PMID: 17277594 143729555
Cross-sectional studies involving elite athletes suggest that muscle size accounts for an even bigger amount of variance in strength than trained people. Human Kinetics PMID: 11990746
Short-term studies with untrained people may not completely capture the influence of hypertrophy on strength, although muscle hypertrophy adds to strength in the long term.
This hypothesis walks a fine line between science and open conspiracy theory. We don’t have a lot of direct data to work with, and the remaining is mostly observational and/or anecdotal.