Why isn't your training working to its full potential? According to Arnold, you're underestimating the very basics!

Nowadays, the market is flooded with "pre-workout" supplements that promise to get you pumped, energized and laser-focused. But Arnold, who even in his 70s supplies his fans with tips through his newsletter Arnold's Pump Club, points out a hidden mistake that up to half of us make.

A mistake you don't know about: Dehydration

Shockingly, according to Arnold and the studies he cites, up to 50% of people start their workouts in a state of dehydration.

We're so obsessed with getting caffeine or a "kicker" that we forget about the most important fluid - water. And the impact on performance is overwhelming. Research suggests that with every percentage of water lost, your performance decreases. So if you arrive at the gym "drained," you start the race with the handbrake on, which no amount of caffeine will release.

"While most pre-workout drinks focus on stimulants to give you an extra boost, how hydrated you are before you start exercising matters a lot more than most people realize," explains Schwarzenegger.

How to fix it? (Arnold's Simple Test)

You don't need any expensive gadgets or complicated protocols. Arnold offers an old but golden rule to make sure you're ready to lift iron: Watch the color of your urine.

Arnold's plan for optimal hydration:

1. The 2-Hour Rule: In the last two hours before your workout, drink fluids as needed.
2. Visual check: Your urine should be a light yellow color. If it's dark, drink more. If it's clear as water, you may be overdoing it, but it's a better option than the opposite.
3. Electrolytes: If you train hard, long (over an hour) or sweat extremely, plain water may not be enough. In this case, Arnold recommends adding electrolytes (sodium, potassium, magnesium) to replenish what you sweat out and prevent cramping or fatigue.

Before you reach for an expensive kicker next time, ask yourself a simple question: Did I drink enough water today? It's the cheapest and most effective "supplementation" you can give your body. As Arnold says, the basics win. And hydration is the foundation of everything.