We've discussed this before. It's in the archives.

Simply put:
> Designer molecules using unrecognizable epitopes, fully immunocompatable
> undetectable synthetic hemoglobin analogs
> recombinant 2,3-BPG.
> lactate shuttle vans
> cardiomyocyte gene therapy (adenovirus vector...ever wonder why these guys always have colds?)
> AI-programmed collagen formulation for optimum tendon elastic modulus
> pulmonary "deshunting" to increase alveolar ventilation and gas exchange
> on the fly blood rheology optimization (third spaced component reservoirs with real time thromboelastography and dosage via voltage controlled lymphovenous valves)
> Van Eck phreaking continuous heart rhythm analysis and optimization
> Nanomanufacturing of carbon frames for piezoelectric "nanomotoring"
> Implanted CN9/CN10 neuromodulators for heart rate control and carotid body baroreceptor decoupling
> Allosteric enzymatic "supercharging" of the electron transport chain via synthetic mitochondrial infusion
> genetic enhancement via crispr-cas9
> nanobot blood boosters with erythropoiesis stimulating nanoparticles
> neural interface augmentation through neuro-silicon mesh implants
> hematopoietic stem cell engineering for enhanced oxygen carrying bio-engineered hyper-aerobic alveoli expansion
> quantum neural control for perfect muscle synchronization and individual muscle fiber control
> nano-pharmacological cognitive enhancers for supraliminal reflexes
> telomere extension therapy for enhanced recovery and virtually eternal longevity
> bioluminescent oxygen release for enhanced energy production
> bio-electronic synaptic boosters
> mitochondrial biogenesis optimization for peak endurance coupled with photosynthetic symbiote
> nano-engineered recovery nanites for rapid healing and on-the-fly ketone assembly
> quantum entanglement-powered telepathic implants for instant subvocal communication
> synthetic muscular myofibril doping and microkevlar tendon coating