Resistance Training Part 8

Hopefully, all of you who have read the last few installments are now practicing what I’ve preached. Simply stated, when you’re in the weight room, you should be training, not lifting, because the effectiveness of your efforts is not dictated by the quantity of weight you can move. Instead, it is the degree of difficulty associated with the lifting that ultimately dictates the gains you will make. Now, lifting heavy weights is certainly challenging, so you might be wondering where the distinction lies. I’m glad you asked!

A number of investigations in recent years have dramatically improved our understanding of what makes muscles respond to resistance training. Findings from the first of these by Shinohara et al. (1998) questioned common beliefs. These researchers recognized that an abundance of empirical evidence supports a relationship between high-resistance training and strength gain. They also acknowledged that high resistance training is characterized by high mechanical stress and then explain how this truth has lead to the assumption that it is high mechanical stress that is the stimulus that causes strength gain. But this had never been proven, so they questioned whether it was really true and to answer that question, had subjects perform resistance training under some very unusual circumstances.

The exercise used by Shinohara et al. was isometric knee extensions, which involve trying to extend your leg against an immovable object. This would be similar to the exercise you perform on a knee extension machine at the gym; however, in this case, the arm of the machine cannot move. Subjects trained both legs this way but, importantly, they did not push as hard as they could in either case. Instead, they only worked at 40 percent of their maximal capacity to extend, which means it was a tame training stimulus to say the least. Nevertheless, one of the legs got stronger and more powerful after four weeks and the intervention that made what should be unproductive strength training effective was something we are all familiar with (or at least should be!). We all know the importance of having our blood pressure checked regularly and to do so, our doctor uses an inflatable cuff that momentarily keeps our blood from following its normal course. Well, in this study, a similar device was used as tourniquet ischemia was applied to one of the legs during the set and that just happened to be the leg that got stronger from the light training.

Sakarada et al. showed that light training was effective for making muscles stronger if blood flow was blocked and in a follow up study by Takarada at al. (2000), researchers tested whether the same would be the case for making muscles bigger. In this investigation, subjects performed dynamic knee extensions (i.e., knee extensions with movement permitted) with 20 percent of the most weight they could perform one strict repetition with. Obviously, this is also a relatively benign training stimulus. They did this once with and once without restricted blood flow and plasma concentrations of growth hormone were measured before and after each workout. The important finding was that 15 minutes post-workout, growth hormone was only elevated when the light training was done with blood flow occluded. And what is more, the increase was larger than what had been reported previously following conventional heavy resistance exercise with short rest intervals between sets (i.e., the type of training that is typically recommended for muscle gain). They also showed that the relative integrated electromyogram was almost twice as large when the knee extensions were performed with restricted flow. This measurement indicates the degree of muscle activation, so this meant that the nervous system had to increase fiber activation to lift a light weight if normal blood flow was not present during the effort.

The conclusion that post-workout growth hormone elevation means a workout is effective for muscle gain must be drawn with caution because it is a hormone’s interaction with receptors and not simply its circulation that is the crucial determinant. However, future studies by Takarada and colleagues would provide confirmation that the expected association with muscle growth was present. Specifically, they measured muscle cross-sectional area by MRI and found that in both healthy, post-menopausal women and elite rugby players, muscles did get bigger from light training if blood flow was restricted while the exercise was being performed. The latter finding was particularly impressive because the athletes had been involved in weight training for five years and, therefore, had a relatively small window for an adaptive response.

Collectively, the results from Shinohara et al. and Takarada et al. indicate that it is not high mechanical stress during resistance training that makes muscles grow bigger and stronger. However, it is interesting to note that when we do lift heavy weights, movement speed is necessarily slow and as each forceful contraction take place, blood vessels are crimped in the surrounding area. This means that blood flow is momentarily blocked during each repetition. Given the findings from these studies, it appears safe to say that this is the critical stimulus that we must achieve when we lift weights. But the next question to answer is why.

This article was originally published in New Living Magazine, which can be accessed on-line at





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