That the brain is the boss of the body is nothing new. But how to trick this all powerful boss into making you stronger that is how you neurohack your workout.
A lot of neurohacks can be done without any equipment. But for the sake of simplicity and safety I will suggest that you buy a mouth guard. Why a mouth guard?
Clenching your jaws can increase strength by up to 10%. This can be done without a mouth guard but to protect your teeth a mouth guard is advised. Although, the clenching seems useful in generating a neurological strength response it seems that the position of the jaw itself is more important. Studies have shown performance increases in both strength and endurance. Meaning, by using a mouth guard you can retrain your jaw position which in turn can improve strength and breathing.
Francis, K T, and J Brasher. “Physiological Effects of Wearing Mouthguards.” British Journal of Sports Medicine 25.4 (1991): 227–231. Print. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1479028/
Shea, Sarah Bowen. “Taking a Bite Out of Sports Stress.” The New York Times, The New York Times, 16 Dec. 2009, www.nytimes.com/2009/12/17/health/nutrition/17fitness.html.