nothing will prepare your muscle for the cascade of activation and motor neuron depletion like the event you're running
cross-train>>
bulk up to put some extra mass on before the competition. this will boost your retention and give you better endurance. heavy lifts to top set. medium and light weight with ballistic reps to high volume will max out muscle building (red and white fibers).
mind your macros and micros>>
stay on top of your nutrition. get ample amounts of your fats, carbs, and protein. take multi's and spread them out through the day. stay on top of your b vitamins throughout the day. top off your protein stores with EAA amino supps. don't drink alcohol. it will deplete your protein severely
My longest tri distance was Olympic and I have done half marathons. Individually, I knew I could do a good time so I just went for the best time in each transitional individual event. Carbo load and hydrate.
Get good at swimming if your aren’t, I did one once and was getting whacked left right and center when I was swimming but if you’re fast you can stay in front of the pack I would think and not get hit by other swimmers
Swimming definitely is the make or break of triathlon. Based on what I have learned, you should focus on swimming. I have heard stories that sound something like "I was dead last when leaving the water, but I overtook about 30 guys on my bike and 10 more on my feet".
edit: I haven't participated in one yet - too bad at swimming
Merida Scultura 5000 (2015)
Merida Big Nine 400 (2019)
Participate in rehearsals or training events. In addition to the main three events, add some cross-training to enhance muscle balance and reduce the risk of injury. I also wear my BP Doctor so that it can monitor my physical condition and exercise status.