Energy & Performance

Frequently asked

Do growth hormone secretagogue peptides like CJC-1295, GHRP-2, GHRP-6, hexarelin, and MK-677 actually build muscle?

Mostly untested for that purpose. Ipamorelin and CJC-1295 have never been tested in a human trial for muscle, strength, or aging outcomes — the only completed trials of these compounds looked at gut motility after surgery or HIV-related fat loss, and the only muscle-relevant evidence is a single mouse study. GHRP-2's only human use is a single diagnostic injection to test pituitary function, and GHRP-6's largest human trials tested it combined with a growth factor for stroke, missing its primary endpoint. MK-677 reliably raises growth hormone and IGF-1 and increased lean mass in a 2-year trial of older adults, but that same trial found no improvement in strength or physical function, plus a rise in blood sugar. Across this whole drug class, researchers found these compounds move hormone levels in blood; what that does for muscle in aging humans specifically is mostly untested or unproven.

Does creatine still work for muscle after age 50?

Yes, but with real limits. A 2025 meta-analysis of 69 trials and 1,937 participants found creatine plus resistance training significantly increased squat strength (+5.64 kg) and bench/chest press strength (+1.43 kg) versus placebo, but when split by age, those gains were significant in younger adults and not in older adults. Separate trials in frail or postmenopausal older women found creatine added nothing measurable on top of resistance training alone, and two years of daily creatine did not improve bone density in 200 postmenopausal women. Researchers describe the effect after 50 as smaller, less consistent, and more dependent on simultaneous resistance training than in younger adults.

Does protein timing matter, or is total daily intake what counts?

Controlled trials that held total protein fixed and only changed how it was spread across the day found no muscle or strength benefit to spreading it out — an 8-week resistance-training trial found no significant difference between eating high-protein meals 3 versus 5 times a day, and a 9-day feeding trial found no difference in muscle protein synthesis across four meal-distribution patterns. A separate trial that instead varied the total daily amount, while holding meal pattern fixed, found a higher total dose (1.5 g/kg/day) produced significantly better whole-body protein balance than a lower one (0.8 g/kg/day). Large observational studies are more mixed on this question, with some tying meal-by-meal frequency to muscle and strength.

What is blood flow restriction (BFR) training, and does it actually work?

BFR training uses an inflatable cuff on a limb to partially restrict blood flow during low-load exercise, typically at 20-40% of a person's one-repetition maximum, to try to trigger the metabolic stress normally associated with heavy loads. A meta-analysis of 10 randomized trials in athletes found BFR combined with resistance training produced meaningful gains in lower-limb strength and muscle size compared with conventional training, and head-to-head trials found low-load BFR can match or nearly match heavy-load training for muscle growth and some performance measures. It has not been shown to improve sport-specific performance beyond conventional training, and one trial found inflating BFR cuffs on older adults' legs acutely worsened their walking balance, with worse effects at higher cuff pressure.

Does caffeine actually improve cognitive performance?

Under genuine sleep deprivation and stress, yes: in 68 Navy SEAL trainees after 72 hours without sleep, 200-300 mg of caffeine significantly improved vigilance, choice reaction time, and learning, in a dose-dependent way. But in everyday, non-extreme settings, much of caffeine's apparent 'boost' may be withdrawal reversal rather than true enhancement — one trial found caffeine improved mood and performance only in habitual coffee drinkers who'd gone without it overnight, not in non-consumers, while a separate similarly designed trial found benefits in both groups, so the two controlled studies disagree. A 2010 Cochrane review of 13 trials found caffeine improved memory, attention, and perception scores but had no effect on verbal functioning and language skills.

Does resistance training still work for building strength after 60, or even in your 90s?

Yes. In one of the earliest controlled trials, ten nursing-home residents averaging 90 years old gained 174% in knee-extensor strength after just 8 weeks of high-intensity training, though muscle size grew far less than strength did. Later meta-analyses of dozens of trials confirm resistance training reliably improves strength and muscle mass in older adults, including those with sarcopenia. But training after 60 isn't identical to training at 25 — a lab study found the cellular signaling that converts a workout into new muscle protein activated in younger muscle after exercise and failed to activate, on the same tests, in older muscle, and not every physical-function outcome, like gait speed, improves as reliably as strength does.

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Start here for plain-English explanations of clinical trials, evidence levels, and how to read a study.