A recent article (published ahead of print) set out to observe the different “effects of high frequency (6x/week) resistance training versus a traditional resistance training frequency (3x/week) on maximal strength and body composition changes in resistance-trained males.”
- The 28 college-aged male subjects underwent 1RM testing of the backsquat, bench press, and deadlift and measured body composition via ultrasound. Trained, as it pertained to this study, required a minimum of 6 months (3days/week) training and minimum existing relative strength of squat 125% body mass, a bench press of 100% body mass, and a deadlift of 150% of their body mass.
- The programs followed a supervised daily-undulating periodization scheme with specificity towards the three main lifts. The 6x/week group completed the same weekly volume by completing half the volume daily and doubling the frequency.
- Both 3x/week and 6x/week significantly increased their squat, bench, deadlift, total, and fat-free mass, neither group edged out in front. Despite this, there were no significant differences between groups.
- “Furthermore, these results indicate that volume appears to be a more important contributor than resistance training frequency to the strength and hypertrophic adaptations observed in response to resistance training.”
- There had previously been some ideas that a higher frequency would attenuate more rapid neural adaptations. Although this study doesn’t support such a theory, hard to dismiss this idea.
- McLester and Guilliams (2000) contradicted these findings by reporting that a 1x/week group only achieved 62% of the strength achieved in the 3x/week group. The current study found only a modest 0.5% increase in powerlifting total, far from significant. 1x/week is certainly too infrequent and the daily volume would most likely be too high for most to handle with strong effort throughout.
- Interestingly enough, “…previous work by Robbins and co-workers (26) reported that while 8 sets of resistance training lead to significantly greater increases in maximal strength than 1 set, there was no statistical difference between a 4 set and an 8 set group.” So we wonder where may the threshold be?
In summary, the biggest take-home point may be that strength is driven by intensity, especially when specific to only three movements. A good start may be training a particular movement about of 3x/week hitting roughly 3-5 sets/movement each day in an undulated fashion. Optimal ranges may differ based on a number of factors such as training age, movement complexity/technicalities, agonists of a movement, and individual anthropometry.
In class we had just began to discuss the stretch-shortening cycle. Unfortunately, we cannot spend as much time on the topic as I would like, since the course objective is to merely introduce students of varying backgrounds to multiple scientific perspectives of kinesiology. Science for Sport put together a nice article summarizing the SSC phenomenon, citing over 40 different papers over the last 30+ years.
- “The action of the SSC is perhaps best described as a spring-like mechanism, whereby compressing the coil causes it to rebound and therefore jump off a surface or in a different direction (Figure 2). Increasing the speed at which the coil is compressed or how hard it is pressed down (amount of force applied) will result in the spring jumping higher or farther. This is known as the ‘rate of loading’ and increasing this will often mean the spring will jump higher or farther. Therefore, a jump which incorporates a ‘run-up’ will often allow an athlete to jump higher or farther than a jump from a static position because of an increase in the rate of loading (6, 7, 8).”
Here are three models of the SSC further defined. In class, I stuck primarily to the first.
Storage of elastic(strain/potential) energy follows a similar mechanism to a rubber band being stretched and snapping back to original shape. Since tendons do not have active sarcomeres that shorten, it is agreed that they are the principal site of elastic energy storage. With this elastic energy, in addition to the concentric propulsion of the muscle leaving the amortization phase, we have large amounts of force being absorbed and even greater magnitudes being concentrically generated.
- “Failing to stiffen during the eccentric and amortization phases, means the performance enhancing effect of the SSC will be lost and the joint would likely collapse. This demonstrates the importance of muscle stiffness during the SSC and its ability to improve performance. It also suggests that athletes’ with higher levels of muscular strength can absorb more force (i.e. higher rate of loading), and therefore have a better ability to use the SSC.”
- “An abundance of research has demonstrated that stronger athletes have a better ability to store elastic energy over weaker individuals (31, 32, 33).”
- “Furthermore, efficient utilisation of the SSC during sprinting has shown to recover approximately 60% of total mechanical energy, suggesting the other 40% is recovered by metabolic processes (34, 35). In aerobic long-distance running, higher SSC abilities have also been shown to enhance running economy – suggesting that athletes with a better SSC capacity can conserve more energy whilst running (33, 36, 37).”
The neurophysiological model focuses on the proprioceptors in musculotendinous units, which are muscle spindles and Golgi tendon organs. Recall, muscle spindles inhibit rapid lengthening in muscle belly intrafusal fibers with a rapid concentric contraction. GTO’s are located within the musculotendinous junction where their “…role is to inhibit (i.e. prevent) the excitation of the muscle spindles during forceful over-lengthening to prevent the possibility of injury (5).”
- Seemingly contradictory, we believe that muscle spindles do not enhance the concentric phase of the SSC, as “many studies have reported no increase in muscle activation after a pre-stretch activity (e.g. CMJ) when compared to non-pre-stretch activity (e.g. SJ) (26, 42, 43). This suggests that muscle spindle reflex activity does not have any impact on the increased force by the SSC (1).”
- Rather, we are training to reduce to the affect of GTO’s as “this would mean that the GTO inhibits the high-muscular stiffness needed during the SSC and therefore reduces the concentric force output and subsequent performance (2).”
- “…4-months of plyometric training has been shown to reduce this GTO inhibitory effect (disinhibition) and increase muscular pre-activity and muscle-tendon stiffness (27). As a result, it appears that effective training methods (e.g. plyometrics) can reduce or even eliminate the potential negative effects observed from the GTO inhibitory effect.”
- “The increase in concentric force output would therefore then lead to an enhanced power output during sporting movements (e.g. jump), and thus may improve performance.”
- To put this simply- the SSC trains to diminish the activity of the GTO, which would otherwise interfere with muscle stiffness and therefore greater force development.
Active state refers to the eccentric phase and amortization phase, think of this as the build-up prior to the explosive concentric contraction.
- “The unpinning belief is that exercises which possess longer eccentric and amortization phases of the SSC will allow more time for the formation of cross-bridges, therefore enhancing joint moments, and thus improving concentric force output.”
- This likely true due to in the increase in joint impulse (force x time).
- Let’s take the high road and say there is certainly an optimal loading time for this phenomenon(maybe even joint/muscle specific), rather than longer eccentric/amortization unconditionally leading to greater force production.
What’s the deal with fiber? With numerous diet trends circulating, it becomes increasing difficult to differentiate which nutritional strategies are ideal, and why they are good in the first place. This article by Carl Zimmer of the New York Times highlights why fiber is linked to lowering rates of diabetes, heart disease, and mortality rates.
- Fiber appears to enhance gut bacteria function, improving the ability of enzymes to breakdown other foodstuffs, therefore improving absorption rates.
- One experiment switched mice from a fiber-rich diet to a low-fiber diet, after a few days “…mouse intestines developed chronic inflammation. After a few weeks, Dr. Gewirtz’s team observed that the mice began to change in other ways, putting on fat, for example, and developing higher blood sugar levels.”
- Another group of rodents were fed a “high-fat menu, along with a modest dose of insulin. The mucus layer in their guts was healthier than in mice that didn’t get fiber, the scientists found, and the intestinal bacteria were kept a safer distance from their intestinal wall.”
- “Once bacteria are done harvesting the energy in dietary fiber, they cast off the fragments as waste. That waste – in the form of short-chain fatty acids – is absorbed by intestinal cells, which use it as fuel.” These short-chain fatty acids also act as signaling agents to regulate immune function.
- In summary, by consuming insufficient fiber, the relationship between gut bacteria, the intestinal wall, and the immune system may be largely disrupted. This may lead to chronic systemic inflammation, insulin resistance, and weight gain.
If there are any particular topics you may be interested in, or believe are worth sharing, related to sport science, exercise physiology, or another sub-discipline of kinesiology, please reach out.