Fid Phil Castro defeated Anthony Gachau via a devastating Technical Knockout (TKO) in the 6th round of their main event heavyweight match at the Vurugu 2 boxing.

Many people were surprised by how quickly Gachau appeared to gas out despite carrying an impressive amount of muscle mass. Being strong and being able to sustain a high pace are two very different things.

Steroids are extremely effective at building muscle size, strength, and explosive power, but they can come at the expense of cardiovascular endurance.

The very physiological changes that help someone become bigger and stronger can also make it harder to maintain performance during prolonged, high-intensity activities such as boxing.

Steroids can cause cardiac hypertrophy. The left ventricle becomes less efficient at relaxing and filling with blood between beats, reducing the amount of oxygen-rich blood that can be delivered throughout the body during intense exercise. In a sport like boxing, where the heart is under constant demand, this can lead to rapid fatigue.

Steroids can dramatically increase muscle size in a relatively short period of time, but the network of tiny blood vessels responsible for delivering oxygen to those muscles does not expand at the same rate. The result is a larger engine demanding more fuel while the fuel delivery system struggles to keep up.

Third, steroid use can increase red blood cell production. While this may initially improve oxygen transport, excessive red blood cell counts can make the blood thicker and more viscous.

Thicker blood is harder for the heart to pump efficiently, especially during intense physical activity, reducing overall endurance and increasing cardiovascular strain.

Steroids are also associated with elevated blood pressure due to increased sodium and water retention. This forces the heart to work harder with every beat. During a boxing match, where heart rates remain elevated for extended periods, that extra strain can accelerate exhaustion.

Another overlooked factor is energy system adaptation. Many steroid users train primarily for maximum strength, power, and muscle growth. Their bodies become highly adapted to short bursts of explosive effort powered largely by glycogen.

Boxing, however, is not a powerlifting competition. It requires sustained aerobic conditioning, efficient oxygen utilization, and the ability to recover repeatedly between exchanges. When an athlete relies heavily on anaerobic energy systems, lactic acid accumulates rapidly, causing the burning sensation and fatigue commonly associated with “gassing out.”

This is why having massive muscles does not automatically translate into superior fight performance. Boxing rewards cardiovascular efficiency, pacing, endurance, and conditioning just as much as it rewards power. A fighter can look physically dominant but still struggle if their cardiovascular system cannot support the demands of the sport.

Of course, only Gachau and his medical team know the exact reasons behind his fatigue on that particular night. Factors such as pacing, preparation, hydration, fight experience, and conditioning also play important roles.