I've long been leery of forced inhalations for breathing development. Stems from singing insights as well as teachers of the Ilsa Gindler school of movement and breathing, as the German-American physical therapy of Caroloa Speads and Elsa Middendorf and Qi Gong (Chi Kung) .
Basically I see them as tightening the chest, reinforcing unhealthy mouth breathing/snoring/apnea, and reducing subtle internal sensing and the longevity that increased FEV1 and Optimal Breathing Work has to offer. Athletes by their competitive nature often suppress many healthy breathing feedback signals. Long after the competition is over these signals stay suppressed and this is one key reason that athletes do not have the extra long lives. that superior conditioning should suggest. Maximum FEV1 gets lost and stays lost.
People with hidden breathing pattern issues many times will not know that the forced inhale is actually tightening their chest and shutting down internal prioceptiveness. They can feel better because of strengthened endogenous breathing and improved gas exchange but the exogenous aspect and its relationship to internal chemistry of easier breathing becomes compromised and invites future problems such as lessened deep relaxation, sub optimal parasympathetic balance and or loss of sense of self.
We strongly advise anyone using a breathing resistance trainer of ANY kind to also use our breathing development techniques and exercises in our Optimal Breathing Kit to offset the chest tensions and breathing restrictions they so often leave in their wake.