08/29/2023
While the current body of research supports how breathing and various cueing techniques can enhance TVA engagement and strengthening, its applications for improving squat performance is scarce. In the presented study, investigators aimed to determine how different bracing and "active exhalation" breathing techniques impacted lower extremity muscle activities during the squat for the purpose of improving their strength (i.e., strength of the hips, quads, etc., not just the core musculature).
There's actually a lot to unpack in the paper, not necessarily for the best reasons of which we will expanded upon in the KAC Blog article "To Breathe Or Not To Breathe", so here's the Coles notes for some practice in interpreting academic research and critical thinking:
Since normalized EMG levels did not exceed 60% MVIC for any muscle group evaluated, its a big reach to suggest superior strategy for the purpose of lower extremity muscle strengthening and will extend to squatting to greater depths and with external bar loading.
Greater EMG activation levels do not necessarily guarantee greater muscle tensions, just like how a statistically significant difference does not guarantee clinically MEANINGFUL differences. We also cannot extend these results to ALL lower extremity musculature; EMG only collected for bi-articular and antagonist muscles. Unlike the primary agonist glute max, vastii and soleus muscles for the squat, the RF, BF, and GAS help coordinate as synergists, and at the same time, as antagonists that increase joint rigidity like the TA. In fact, the RF has been shown to minimally contribute to knee extensor joint moments during the squat.
THIRD. Although greater co-activity does technically increase stability, let me put it to you this way: mobility impaired geriatric older adults tend to have the highest co-contraction levels of all to compensate for reduced strength, force control and proprioception. Would it not make more sense to prioritize eccentric strengthening of muscles that matter like the vastii to control the knee rather than relying on higher hamstring co-contraction to compensate?
What do you think?