Sports Nutrition Pre-Workout Products: what Claude and GPT would buy

Two AI models chose on their own, with no web access. Nobody tested these products: this is what each one says, and how to check it.

They disagree: Claude chooses Legion and GPT chooses Optimum Nutrition

In Health & Household, Claude and GPT choose the same brand in 14 of 26 categories.

Claude Opus 5.5 · October 28, 2026

Legion Pulse (line)

Pulse lists its full formula with no proprietary blend, and its citrulline, beta-alanine and caffeine are dosed near the amounts used in research rather than sprinkled in for the label.

Not for: People who are caffeine-sensitive or take other stimulants (choose a stim-free version), people who dislike the skin tingle from beta-alanine, and anyone pregnant or with heart or blood-pressure conditions.

GPT 6.1 Sol · November 10, 2026

Optimum Nutrition Gold Standard Pre-Workout (line)

A straightforward formula with moderate caffeine, creatine, and beta-alanine from an established sports nutrition brand.

Not for: Minors, pregnant people, or anyone sensitive to caffeine.

Claude also picks Optimum Nutrition for “gentle, widely available starter”.

Which one fits you

stimulant-free or evening training

Transparent Labs Stim-Free Pre-Workout (line)

It keeps a fully disclosed, effectively dosed pump and endurance formula with no caffeine, so it suits late sessions and caffeine-sensitive users.

Not for: Anyone who wants the alertness kick of caffeine before training.

gentle, widely available starter

Optimum Nutrition Gold Standard Pre-Workout (line)

It is a moderate-stimulant formula from a mainstream brand and suits first-time users who want to test their tolerance.

Not for: Experienced users who want full research doses of citrulline in a single scoop.

Check before you buy

Caffeine per serving. Roughly 3 to 6 mg per kg of body weight is the researched range, which is about 150 to 300 mg for most adults; keep total daily caffeine within 400 mg. Caffeine drives most of the performance effect, and above this range you get more jitters and worse sleep with little added benefit.
Citrulline dose. About 6 to 8 g of citrulline malate, or about 6 g of L-citrulline, per serving. Many formulas include citrulline for the label at a fraction of the studied dose.
Beta-alanine dose. About 3.2 g per serving, or 3.2 to 6.4 g per day taken consistently. It works by building up in muscle over weeks, so underdosing it makes it pointless; the tingle it causes is harmless.
Label transparency. Every ingredient should be listed with its own amount, with no proprietary blend. With a blend you cannot tell whether any ingredient is present at a dose that works.
Third-party testing. Tested athletes should require NSF Certified for Sport or Informed Sport certification. Pre-workouts are the supplement class most often found contaminated with banned stimulants.

Where to find Legion Pulse

Legion Athletics
GNC
Vitacost

Shops seen in search results on November 6, 2026. A shop missing here may sell it too. Nothing was checked by a person.

Brands that matter

Legion: Transparent, clinically dosed formulas with both stim and stim-free versions.
Transparent Labs: No proprietary blends; strong stim-free option.
Optimum Nutrition: Mainstream brand with milder, entry-level pre-workouts.
Ghost: Popular flavors and a disclosed label, but check doses against the criteria.

What to avoid

Proprietary blends that hide individual ingredient amounts.
Products with multiple stacked stimulants or unfamiliar stimulant compounds.
Single servings above about 300 mg of caffeine, especially for first-time users.
Formulas built around L-arginine as the pump ingredient instead of citrulline.

Questions

Is the tingling feeling dangerous?

No. It comes from beta-alanine and is harmless; splitting the dose or taking it with food reduces it.

Do I need to cycle off pre-workout?

The main reason to cycle is caffeine tolerance; periodic breaks or lower-caffeine days restore the effect.

Sports Nutrition Pre-Workout Powders

Nearly all pre-workouts are sold as powders, so the parent pick and criteria apply directly: choose a fully disclosed label with researched caffeine, citrulline and beta-alanine doses, or a stim-free version if caffeine is a problem.

All of Sports Nutrition Products