r/exercisescience

My knee joints making sounds when I do squats, this means am I doing the squats wrong or it is normal to hear those sounds?

I really enjoy running and golf during the activity, but after I feel like a gazelle and too calm.

But gym, even though it may not be as fun (although I love the pump), I feel like a LION afterwards and want to conquer the world.

Anyone else have this conflicting thing and feel this way? This is why I am sticking to gym.

Simple Summary

A meta-analysis of 49 studies with 1,863 participants shows 1.6 g/kg/day (0.73 g/lb/day) is the point of diminishing returns for muscle gain. For a 180 lb (82 kg) person, that is about 130 grams per day. Beyond this, additional protein has not been shown to increase muscle mass.

Per meal, roughly 0.4 g/kg (0.18 g/lb), about 30-40 grams for most people, across 4 meals gets you to 1.6 g/kg/day. The idea that the body cannot use more than 30 grams of protein per meal is incorrect. It originated from studies using fast-digesting whey in isolation; whole food protein digests over several hours and larger per-meal doses are not wasted.

Protein timing around training has no detectable effect on muscle growth when total daily intake is adequate. Two meta-analyses and a direct trial support this.

Plant protein produces equivalent results to animal protein when total intake is matched.

During a caloric deficit, evidence is weaker but suggests 2.0-2.5 g/kg/day (0.91-1.14 g/lb/day) may help preserve lean mass.

Things the evidence does not support: BCAA or leucine supplementation beyond what adequate total protein provides, precise peri-workout timing windows, or any hard cap on protein utilization per meal from whole foods.

A Deep Dive into the Data (The summary above explains everything below)

1: THE GOLD STANDARD

Morton et al 2018 (PMID 28698222): Published in British Journal of Sports Medicine. Systematic review, meta-analysis, and meta-regression of 49 RCTs, n = 1,863. The definitive paper on this question.

Key finding: Protein supplementation significantly increased fat-free mass by 0.30 kg (0.66 lb; 95% CI 0.09 to 0.52 kg, p < 0.05). The meta-regression showed a ceiling: FFM gains increased with protein intake up to approximately 1.62 g/kg/day (0.73 g/lb/day), after which no further benefit was observed. The slope flattened to near zero. Additional findings: benefit of supplementation on FFM declined with age (-0.01 kg/yr [-0.022 lb/yr], p = 0.002) and was larger in trained individuals (0.75 kg [1.65 lb], p = 0.03).

What this means: At 1.6 g/kg/day you capture essentially all the muscle-building benefit protein can provide. The 0.30 kg average effect includes studies where baseline protein was already adequate; effects were larger when baseline intake was low.

Study design: Tier 5 (meta-analysis with meta-regression). Allows seeing the dose-response shape rather than just a binary yes/no. Limitations: dietary intake was self-reported in most trials; most studies were 6-12 weeks. Author SMP has received funding from the US National Dairy Council.

Jäger et al, ISSN Position Stand 2017 (PMID 28642676): Published in JISSN. Official ISSN position after comprehensive review. Recommendations: 1.4-2.0 g/kg/day (0.64-0.91 g/lb/day) for building muscle; 2.3-3.1 g/kg/day (1.04-1.41 g/lb/day) during hypocaloric periods. Per-meal: 0.25-0.40 g/kg (0.11-0.18 g/lb), or 20-40g absolute. Total daily intake dominates over timing. The ISSN range brackets Morton's 1.6 g/kg almost perfectly, giving us two independent sources converging on the same number.

Study design: Tier 9 (expert position stand). Industry-adjacent (supplement companies sponsor ISSN conferences), but recommendations are conservative and align with the independent Morton MA.

2: PER-MEAL DOSING

Schoenfeld and Aragon 2018 (PMID 29497353): Published in JISSN. Narrative review that directly addressed the "you can only absorb 20-30g per meal" claim. MPS is maximized at roughly 0.24-0.40 g/kg/meal (0.11-0.18 g/lb), or 20-35g for an 80 kg (176 lb) person. But whole-food protein digests over 3-6 hours, not 90 minutes like isolated whey. A 50g protein meal from steak is not wasted. Recommendation: 0.4 g/kg/meal across 4 meals to reach 1.6 g/kg/day. For 80 kg (176 lb): 32g x 4 meals.

Layman et al 2015 (PMID 25926513): Published in American Journal of Clinical Nutrition. Established the metabolic framework: the per-meal anabolic threshold is roughly 30g of high-quality protein containing 2.5-3g of leucine, the primary mTORC1 trigger. Animal proteins hit this threshold at lower total grams than most plant proteins, which is why protein quality matters, not a reason to supplement free leucine.

Wilkinson et al 2023 (PMID 37537134): Published in Physiological Reports. Systematic review. No significant association between leucine dose and post-exercise MPS rates when total protein was 20g or more. Once you eat enough total protein, leucine takes care of itself. Free leucine or BCAA supplementation on top of adequate protein provides no additional benefit.

3: DOES TIMING MATTER?

Schoenfeld, Aragon, and Krieger 2013 (PMID 24299050): Published in JISSN. Meta-analysis: 478 subjects and 96 effect sizes (strength), 525 subjects and 132 effect sizes (hypertrophy). When controlling for total protein intake, no significant effect of timing on strength or hypertrophy. Total protein intake was the strongest predictor of effect size. The "anabolic window" is a marketing invention. Having protein within 2-3 hours post-exercise is reasonable; urgency is not.

Schoenfeld et al 2017 (PMID 28070459): Published in PeerJ. RCT, n = 21 trained men, 10 weeks. 25g protein immediately pre vs post exercise. No significant differences in any measure of strength, hypertrophy (ultrasound), or body composition. The exact minute does not matter. Study design: small RCT, underpowered, but null result is consistent with the meta-analysis.

4: PRE-SLEEP PROTEIN

Kouw et al 2017 (PMID 28855419): Published in Journal of Nutrition. Double-blind RCT, n = 48 healthy older men (mean age ~72). 40g casein before sleep increased overnight MPS versus placebo. Protein is effectively digested and used during sleep. Most relevant for older adults with anabolic resistance.

Trommelen et al 2023 (PMID 36857005): Published in Sports Medicine. RCT, n = 36 young men. Pre-sleep casein increased both myofibrillar and mitochondrial protein synthesis during overnight recovery. Confirms the strategy works in young populations too.

What this means: Pre-sleep protein works mechanistically, but no long-term training study has shown it adds hypertrophy beyond an already-adequate 1.6 g/kg/day total intake. It is a tool for those struggling to hit their daily target, not a requirement.

5: HOW HIGH IS TOO HIGH?

Antonio et al 2015 (PMID 26500462): Published in JISSN. RCT, n = 48 trained men and women. Compared 3.4 g/kg/day (1.54 g/lb/day) vs 2.3 g/kg/day (1.04 g/lb/day) with heavy resistance training.

Key finding: Both groups gained identical FFM: +1.5 kg (+3.3 lb) in both groups (mean ± SD: +1.5 ± 1.8 kg NP, +1.5 ± 2.2 kg HP; non-significant group difference). The HP group lost more fat (-1.7 kg [-3.7 lb] vs -0.3 kg [-0.66 lb]) and body fat percentage (-2.4% vs -0.7%). Strength gains were equal. Eating 1.1 g/kg/day more protein added zero additional muscle. Both intakes are above Morton's plateau, confirming the ceiling is real.

Bagheri et al 2024 (PMID 39206316): Published in Frontiers in Nutrition. RCT, n = 48 trained young men, 16 weeks. 1.6 vs 3.2 g/kg/day (0.73 vs 1.45 g/lb/day). No significant additional benefit of doubling the dose for lean mass, strength, endurance, or power. Replicated Antonio and Morton with longer duration and direct dose comparison.

Limitations for both: n = 48 underpowered for small effects. A 0.1 kg (0.22 lb) benefit over 16 weeks would be undetectable, but an effect that small is practically irrelevant.

Anyone claiming 1g per pound (2.2 g/kg/day) is already above the evidence-based ceiling. 1.5g per pound (3.3 g/kg/day) is bro-science.

6: DISTRIBUTION AND PROTEIN SOURCE

Tavares et al 2025 (PMID 40673785): Published in Journal of Sports Medicine and Physical Fitness. RCT, 8 weeks. Protein distribution pattern did not significantly affect lean mass or strength gains when total intake was adequate. You do not need exactly 4, 5, or 6 meals; 3-4 protein-containing meals across the day is sensible, but total daily dose dominates.

Hindermann Santini et al 2025 (PMID 41059835): Published in JISSN. RCT. Animal vs plant protein blends produced similar effects on strength and hypertrophy when total protein was matched. Plant protein is not inferior for muscle building with adequate total intake. Also supported by Goldman et al 2024 (PMID 38674813), a modeling study in Nutrients showing plant-based diets meeting energy requirements can supply enough protein and leucine for maximizing hypertrophy.

7: THE RDA IS TOO LOW

Tagawa et al 2025 (PMID 40914512): Published in Journal of Nutrition. Umbrella review: 43 NB articles (777 participants) vs 17 IAAO articles (186 participants). Pre-registered PROSPERO CRD42025636735.

Key finding: IAAO mean was 0.88 g/kg/day (0.40 g/lb/day; 95% CI 0.85 to 0.90) vs NB mean 0.64 g/kg/day (0.29 g/lb/day; 95% CI 0.61 to 0.68) for nonathletes, 36% higher. For athletes: IAAO 1.61 (0.73 g/lb/day; 95% CI 1.44 to 1.78) vs NB 1.27 (0.58 g/lb/day; 95% CI 1.06 to 1.47), 27% higher. Overall ~30% higher by IAAO.

The RDA of 0.8 g/kg/day (0.36 g/lb/day) was built on nitrogen balance, which this review shows systematically underestimates requirements. Applying the RDA safety margin (97.5th percentile) to the IAAO mean produces roughly 1.0-1.1 g/kg/day (0.45-0.50 g/lb/day) for the general population. Even sedentary adults likely need more than the current RDA. Athletes need substantially more, consistent with ISSN and Morton. Tier 2 evidence. Limitation: IAAO literature is small (186 participants vs 777 for NB); co-authors from Meiji Co Ltd (dairy company) disclose employment.

8: EVIDENCE GAPS

Caloric deficit data is thin. The ISSN's 2.3-3.1 g/kg/day cutting recommendation derives from a handful of small studies. Optimum intake during a cut is less certain than for maintenance or surplus.

Older adults may need more per meal (0.4-0.6 g/kg [0.18-0.27 g/lb] vs 0.25-0.4 [0.11-0.18] for young adults) due to anabolic resistance, but long-term hypertrophy trials in older populations are lacking.

Women are underrepresented. Most dosing studies used male participants; direct dose-response data in women is scarce.

No data beyond 16 weeks exists. A small benefit of very high protein compounding over years is theoretically possible but unsupported and the burden of proof is on that claim.

Individual variability is real and poorly quantified. 1.6 g/kg/day (0.73 g/lb/day) is a population plateau, not a personalized prescription. If you are gaining at 1.4 g/kg (0.64 g/lb), fine. If plateaued at 1.6, pushing higher is unlikely to fix it.

9: THE BOTTOM LINE

Total daily: 1.6 g/kg/day (0.73 g/lb/day). 2.0 g/kg/day adds negligible benefit. Above 2.3 g/kg/day adds zero benefit in every study that tested it.

Per meal: ~0.4 g/kg (0.18 g/lb) across 3-4 meals. For 80 kg (176 lb): ~32g x 4 meals = 128g total.

Protein quality: any complete source works. Plant protein achieves equivalent results when intake is matched; complementary combinations (pea + rice, soy) compensate for lower per-gram quality.

Timing: secondary. Consume within a few hours of training as habit; do not stress about windows. Pre-sleep protein is a useful tool for those struggling to hit total intake.

Cutting: aim 2.0-2.5 g/kg/day (0.91-1.14 g/lb/day). Evidence is weaker here.

Does not matter: BCAAs, leucine pills, precise 30-60 minute windows, fear of wasting protein above 30g per meal from whole foods, fear that plant protein is inferior when intake is matched.

If someone is selling a supplement, a timing protocol, or a fear of wasted protein, the evidence does not support their product.

10: STATISTICS NOTE

Numbers verified directly against PubMed abstracts:
- Morton 2018: n = 1,863 (49 studies), FFM 0.30 kg (95% CI 0.09 to 0.52), p < 0.05, plateau at ~1.6 g/kg/day, age effect -0.01 kg/yr (p = 0.002), trained benefit 0.75 kg (p = 0.03). Exact CI for plateau point and individual FFM p-value require full-text.
- Schoenfeld 2013: 478 subjects / 96 ESs (strength), 525 / 132 ESs (hypertrophy), null finding when controlling for total protein. Exact ES and p-values require full-text.
- Antonio 2015: n = 48, NP 2.3 vs HP 3.4 g/kg/d, FFM +1.5 kg both groups (non-significant), HP lost more fat (-1.7 vs -0.3 kg) and body fat % (-2.4% vs -0.7%). Duration and kcal difference require full-text.
- Tagawa 2025: 43 NB (777 participants) vs 17 IAAO (186 participants). IAAO nonathlete mean: 0.88 g/kg/d (95% CI 0.85 to 0.90) vs NB 0.64 (95% CI 0.61 to 0.68). Athletes: IAAO 1.61 (1.44 to 1.78) vs NB 1.27 (1.06 to 1.47). ~30% higher overall. PROSPERO CRD42025636735.

Qualitative findings from abstracts (exact statistics require full-text):
- Schoenfeld 2017 (n = 21), Bagheri 2024 (n = 48), Hindermann Santini 2025, Tavares 2025: all reported null results for primary comparisons.
- Wilkinson 2023: null finding on leucine dose-MPS association above 20g protein (no pooled estimate).
- Kouw 2017 (n = 48), Trommelen 2023 (n = 36): positive pre-sleep MPS findings.
- Schoenfeld & Aragon 2018, Layman 2015, Reidy & Rasmussen 2016: narrative reviews, no pooled statistics.

No numbers were fabricated or estimated. All 18 PMIDs verified against PubMed, May 14 2026. Every PMID resolves to correct paper with matching authors, journals, and years.

Hello everybody. We know from researchers that a multi frequency approach is optimal to achieve hypertrophy, like training muscles twice per week. I tried this for years and always ended up feeling more tired and never progressing. Since few months I started listening more to my body and ended up training each muscle group once per week. I would rotate push ( pectoral and shoulders), leg (squat pattern), pull (back and biceps), leg (hinge pattern), training three per week. I improved all the lifts and gained more muscle. What's your experience or preferences about training frequency?

Hi,

Are there any good sources on muscles per limb/ section of the body and how they work together in relation to workouts?

There is a lot of content online like: “you’ll only ever need these x exercises for your *legs/back/arms/chest/whatever*

And then there seem to be a million different exercises for each individual muscle that “needs to be worked” one even better (S tier) over the ones you never should do.

I don’t want to become a physical therapist, but I would like to know more about muscles, how they work together, so I know better what I’m doing.

Hello everyone, relatively new to the chat, idk if I would call my self an advanced runner but im attempting.

That being said, I have been having an issue for the past few months and in really not sure what it could be or not, I've had a few at look at the issue and all
Come up with different ideas but no success so far.

My current issue is that when I run it feels as if my adductor becomes an over rigged guitar string being plucked as I run eventually leading to my gait being super short or not allowing me to open up in stride at all with out it feeling like its locking my knee up. I don't really notice it when sprinting as u play university soccer but any long distance work has become little by little less enjoyable due to the fact each day is different with it, I've tried taking weeks, months off, stretching and a bit or massages and nothing so far. Im running outta ideas and love for running.

If anyone one has any idea of any solution please feel free to chime in, or ask for further information.

Thank You guys

:)