Monthly Archives: October 2015

Core Muscle Activity, Exercise Preference, and Perceived Exertion during Core Exercise with Elastic Resistance versus Machine

Probably one of the best research articles I´ve read in while.
Granted, such exercise-specificity is probably rarely needed, but it´s nice to know which muscles an exercise is actually targeting.

Generally, complex exercises such as the squat and deadlift will activate the core musculature to a similar degree as core-specific exercises. However, many prefer to finish their workout-session with a bit of disco/beach-specific work, which is where the exercise-evaluation studies can help guide towards the most efficient exercises and/or training modalities.

Full text is available.

Abstract:

Objectives. To investigate core muscle activity, exercise preferences, and perceived exertion during two selected core exercises performed with elastic resistance versus a conventional training machine.

Methods. 17 untrained men aged 26–67 years participated in surface electromyography (EMG) measurements of five core muscles during torso-twists performed from left to right with elastic resistance and in the machine, respectively. The order of the exercises was randomized and each exercise consisted of 3 repetitions performed at a 10 RM load. EMG amplitude was normalized (nEMG) to maximum voluntary isometric contraction (MVC).

Results. A higher right erector spinae activity in the elastic exercise compared with the machine exercise (50% [95% CI 36–64] versus 32% [95% CI 18–46] nEMG) was found. By contrast, the machine exercise, compared with the elastic exercise, showed higher left external oblique activity (77% [95% CI 64–90] versus 54% [95% CI 40–67] nEMG). For the rectus abdominis, right external oblique, and left erector spinae muscles there were no significant differences. Furthermore, 76% preferred the torso-twist with elastic resistance over the machine exercise. Perceived exertion (Borg CR10) was not significantly different between machine (5.8 [95% CI 4.88–6.72]) and elastic exercise (5.7 [95% CI 4.81–6.59]).

Conclusion. Torso-twists using elastic resistance showed higher activity of the erector spinae, whereas torso-twist in the machine resulted in higher activity of the external oblique. For the remaining core muscles the two training modalities induced similar muscular activation. In spite of similar perceived exertion the majority of the participants preferred the exercise using elastic resistance.

 

 

Electronic devices before sleep?

Bad idea!

Unless you are taking the cave/paleo thingy way to seriously, you´ll have heard that it´s a good idea to limit exposure to light (especially blue light) before going to bed. Then again, it is estimated that 90% of the (American) population use some type of electronics before bedtime, so it might just (once again!) come down to plain old stupidity and/or a disinterest in ones own health.

People tend to focus loads on nutrition and exercise, but fail to recognise that poor sleep may severely diminish the positive effects of doing right in these two arenas.

 

The short abstract below is indeed worth reading, as it sums up a very interesting study examining the effects of looking at your electronic devices before bedtime.

 

The use of light-emitting electronic devices for reading, communication, and entertainment has greatly increased recently. We found that the use of these devices before bedtime prolongs the time it takes to fall asleep, delays the circadian clock, suppresses levels of the sleep-promoting hormone melatonin, reduces the amount and delays the timing of REM sleep, and reduces alertness the following morning. Use of light-emitting devices immediately before bedtime also increases alertness at that time, which may lead users to delay bedtime at home. Overall, we found that the use of portable light-emitting devices immediately before bedtime has biological effects that may perpetuate sleep deficiency and disrupt circadian rhythms, both of which can have adverse impacts on performance, health, and safety.

Chang et al., 2015