you might want to clarify what you mean buy toughest.
Physical endurance its MX and then soccer. Thats what the studies say not just an opinion.
When I was much younger I lived to ride. Did the amatuer thing
here in Tx.
World class Mx (outdoor-not SX) used to be 2 45 minute +2 lap motos No breaks.Go as hard as you can.
Even the peloton crowd go out slow.
The Bullshit stops when the gate drops boys and girls.
Jim knows
Lickmymonster