Sarcoplasmic Hypertrophy Is Real, But Is It Relevant?
After years of people claiming that it was bro science, a recent study provides further evidence that sarcoplasmic hypertrophy is a real phenomenon. The details, however, are still murky. for sale drostanolone propionate
This article is a review and breakdown of a recent study. Haun et al. (2019)
Key points
In a reanalysis of data from a previous study, it was found that subjects who had significant increases in muscle fiber cross-sectional area also tended to have decreases in actin and myosin (contractile protein) concentrations, and therefore a relative increase the proportion of the muscle fiber composed of sarcoplasm.
In other words, this study provides solid evidence of sarcoplasmic hypertrophy.
What are the causes of sarcoplasmic hypertrophy? How could we train to achieve it (or avoid it)? These are still open questions, but we are at the point where we can make some plausible assumptions.
Sarcoplasmic hypertrophy has been a bugbear of the evidence-based fitness world for years. Considered the stuff of muscle magazine legend, it has long been ignored with little more than mockery. However, a recent study (1) has provided further convincing evidence of the phenomenon's existence. I say "further" evidence, because the first study demonstrating sarcoplasmic hypertrophy is 50 years old, but the good references were so few and far between that it was not taken seriously.
Just to make a backup, what does "sarcoplasmic hypertrophy" mean? To keep things simple, muscle fibers have a lot of structures called myofibrils, which are mainly composed of the contractile proteins actin and myosin. The rest of the substance within the muscle fiber is called sarcoplasm, which is made up of organelles, proteins, glycogen, water, and a bunch of other various non-contractile elements. As a fiber grows, it is generally assumed that the proportion of the fiber composed of myofibrils remains the same or increases; which would be called "myofibrillar hypertrophy". If, on the other hand, the fiber grows, but the proportion of the fiber composed of myofibrils decreases, this means that the sarcoplasm has expanded at a faster rate than the myofibril pool; this is sarcoplasmic hypertrophy.
In the study currently reviewed (1), 15 men were analyzed who had large increases in the cross-sectional area of muscle fibers after a six-week high-volume training program. The density of contractile proteins (actin and myosin) in their muscle fibers decreased, indicating that sarcoplasmic hypertrophy had occurred. So why did this happen? What implications does this have for the design of training programs? There are many open questions, but I think we can make some plausible assumptions. Read on to learn more.
Purpose and hypothesis
Scope
The aim of this study was to study the changes in mitochondrial volume and contractile, sarcoplasmic and glycogen protein concentrations that occur with hypertrophy.
Hypothesis
The authors hypothesized that subjects would experience a decrease in muscle actin and myosin concentrations, a decrease in citrate synthase activity (suggesting a decrease in mitochondrial density), and no change or increase in glycogen and sarcoplasmic protein concentrations. .
Subjects and methods
Subjects
This study is a continuation of the work done in a previous study (2), which was extensively explained here by the study's lead author. The subjects in that previous study were 31 young men with at least one year of training experience and a minimum squat of 1.5 times body mass. In the current study, the subjects were the 15 people in the previous study who had noticeable increases (> 320μm2) in the cross-sectional area of the muscle fibers.
Study design
In the initial study (2), the training program consisted of three training sessions per week for six weeks, consisting of five different exercises. This study was primarily based on data collected from vastus lateral (quadrilateral) biopsies, so for our purposes here, we will focus only on the squat training of the study. Throughout the study, squat training consisted of sets of 10 with 60% 1RM. In week 1, subjects performed 10 total sets of squats (4 on day 1, 2 on day 2, and 4 on day 3). The volume was increasing every week, so by week 6 they were doing 32 sets of squats (12 on day 1, 8 on day 2, and 12 on day 3).
Researchers performed vastus lateralis biopsies and blood draws before the start of the training protocol, after three weeks of training, and after six weeks of training. Biopsies were performed 24 hours after the last training session in weeks 3 and 6, then to examine the effects of recovery after the training program.
