“…This process results in an elevation of serum urea nitrogen levels [ 32 ], which can further promote muscular fatigue and reduce exercise endurance [ 33 ]. Lack of sleep also has a deleterious effect on metabolic function, leading to an increase in serum urea nitrogen content [ 34 ]. Furthermore, both high-intensity exercise and insomnia can trigger oxidative stress, damaging organs, cells and macromolecular substances [ [35] , [36] , [37] ].…”