What is interesting is to see effect size. For example, exercise would produce huge effect in blood content that transports oxygen and relatively small effect o

What is interesting is to see effect size. For example, exercise would produce huge effect in blood content that transports oxygen and relatively small effect on brain-derived neurotrophic factor. For humans BDNF measures in 39 nanogramms per millilitre [1] - it is highly dissolved. I seriously doubt that masspectrometry can handle this. [1] https://www.hindawi.com/journals/bmri/2013/901082/ https://www.hindawi.com/journals/bmri/2013/901082/ Also, [2] - the BDNF level for sprint runners is more than 5 (five) times higher than of sedentiary people for Olympic team members. [2] https://www.researchgate.net/publication/51658551_Increased_basal_plasma_brain-derived_neurotrophic_factor_levels_in_sprint_runners https://www.researchgate.net/publication/51658551_Increased_... I guess the ability to run marathon every night can easily put one into Olympic team. ;)