Category Archives: Research

Importance of mind-muscle connection during progressive resistance training

… is the head-turning title of yet another really nice article in a series that seems never-ending. – I am sure Jimmy agrees.

Basically, the study by Calatayud et al. 2015 sought to evaluate wether focusing on specific muscles during the bench press exercise can selectively activate these. As the abstract below shows, the results are quite interesting.

In short, it seems that focusing on a specific muscle will increase the activity of this muscle, without decreasing the activity of other prime-movers. In contrast, when specifically focusing on the triceps muscle during benchpress and hereby increasing the activity, the activity of the pectoralis muscles were also increased at loads corresponding to 50% and 60% of 1RM.

Note that this effect seems to “wear off” when playing around with higher loads (80% of 1RM), so it´s something that could, and should, be used for your training sessions focusing on power.

 

METHODS:

Altogether 18 resistance-trained men participated. Subjects were familiarized with the procedure and performed one-maximum repetition (1RM) test during the first session. In the second session, 3 different bench press conditions were performed with intensities of 20, 40, 50, 60 and 80 % of the pre-determined 1RM: regular bench press, and bench press focusing on selectively using the pectoralis major and triceps brachii, respectively. Surface electromyography (EMG) signals were recorded for the triceps brachii and pectoralis major muscles. Subsequently, peak EMG of the filtered signals were normalized to maximum maximorum EMG of each muscle.

RESULTS:

In both muscles, focusing on using the respective muscles increased muscle activity at relative loads between 20 and 60 %, but not at 80 % of 1RM. Overall, a threshold between 60 and 80 % rather than a linear decrease in selective activation with increasing intensity appeared to exist. The increased activity did not occur at the expense of decreased activity of the other muscle, e.g. when focusing on activating the triceps muscle the activity of the pectoralis muscle did not decrease. On the contrary, focusing on using the triceps muscle also increased pectoralis EMG at 50 and 60 % of 1RM.

CONCLUSION:

Resistance-trained individuals can increase triceps brachii or pectarilis major muscle activity during the bench press when focusing on using the specific muscle at intensities up to 60 % of 1RM. A threshold between 60 and 80 % appeared to exist.

 

 

 

 

 

Electromyographic comparison of elastic resistance versus machine exercise for high-intensity strength training in chronic stroke patients

 

Another really nice study was just published in “Archives of Physical Medicine and Rehabilitation”. The study from Vinstrup et al. 2015 examines differences in muscle activation during knee flexion- and extension with two different training modalities; conventional machine training and Theraband elastic tubing.

Physiotherapists working with chronic stroke patients should use this knowledge to apply best practices of rehabilitation following stroke. More on this topic will follow.

 

Abstract:

Objective

To investigate whether elastic resistance training can induce comparable levels of muscle activity as conventional machine training in chronic stroke patients.

Design

Comparative study

Setting

Outpatient rehabilitation facility

Participants

18 stroke patients with hemiparesis (mean age 57 (SD: 8) years).

Interventions

Patients performed 3 consecutive reps at 10 repetition maximum (RM) of unilateral knee extension- and flexion, using elastic resistance and conventional training machines.

Main outcome measure

Surface electromyography (EMG) was measured in vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF) and semitendinosus (ST), and normalized to the maximal EMG (nEMG) of the non-paretic leg.

Results

In the paretic leg, agonist muscle activity ranged from 18-24% nEMG during knee flexion and 32-40% nEMG during knee extension. For the latter, VL nEMG was higher during machine exercise compared with elastic resistance (40% [95% CI 33 – 47] vs 32% [95% CI 25 – 39], P=0.003). In the non-paretic leg, agonist muscle activity ranged from 54-61% during knee flexion and 52-68% during knee extension (n.s.). For knee flexion, ST nEMG was higher (61% [95% CI 50 – 71] vs 54% [95% CI 44 – 64], P=0.016), and for knee extension VM nEMG was higher (68% [95% CI 60 – 76] vs 56% [95% CI 48 – 64], P<0.001) during machine exercise compared with elastic resistance. By contrast, antagonist co-activation was significantly higher during knee flexion with elastic resistance compared with the machine. Lastly, there were no differences in perceived exertion between exercise modalities.

Conclusion

Machine training appears to induce slightly higher levels of muscle activity in some of the investigated muscles compared to elastic resistance during lower-limb strength training in chronic stroke patients. The higher level of co-activation during knee flexions with elastic tubing suggests that elastic resistance exercises are more difficult to perform. This is likely due to a higher level of movement instability.

 

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.