Physiology

1. Physiologypreliminary · human dataAdded 6 August 2026

   Lifting raises IGF-1 after 60, lowers it before

   Pooling 22 studies with 680 participants, resistance training was associated with higher serum insulin-like growth factor 1 in people older than 60, in both men and women, while participants younger than 60 showed lower IGF-1. The effect appeared at training durations both under and over 16 weeks.

   ⚠What it shows: Meta-analysis of 22 mostly small studies totalling 680 participants, searched to May 2020. It pooled a continuous blood marker using odds ratios, an unusual approach, and IGF-1 is a circulating marker rather than a measure of strength, muscle mass or health outcomes. The reversal in under-60s was unexpected and is not explained.Meta-analysis · Aging Male

   Full breakdown →Resistance training effect on serum insulin-like growth factor 1 in the serum: a meta-analysis. Aging Male 2020
2. Physiologypreliminary · human dataAdded 29 July 2026

   Lactate dwarfs other markers of exercise stress

   Pooling 110 studies and 1,826 participants, blood lactate showed by far the largest acute post-exercise response (response ratio 4.43), ahead of IL-6, creatine kinase and LDH, but the authors stress none of these has been shown to be specific to fatigue.

   ⚠What it shows: Systematic review and random-effects meta-analysis of 110 articles, 129 experiments, 1,826 healthy participants, with very high heterogeneity (I² 87-98%); the attached LC-MS pilot involved only seven healthy young men and was exploratory.Review · Metabolites

   Full breakdown →Lactate threshold explained →Recovery Readiness Index →Candidate Metabolic Biomarkers for Physical Fatigue Assessment: An Integrative Meta-Analysis and Exploratory Liquid Chromatography-Mass Spectrometry Pilot Study of Acute Exercise Responses. Metabolites 2026
3. Physiologypreliminary · human dataAdded 29 July 2026

   Ageing muscle loses strength partly via the nerves

   Pooling 48 studies, a meta-analysis found older adults had markedly lower maximal strength than younger adults (SMD -1.01) alongside lower motor unit discharge rates, especially at high forces, plus greater discharge variability and lower relative recruitment thresholds. The authors suggest altered motor unit behaviour contributes at least partly to age-related strength loss.

   ⚠What it shows: Systematic review and meta-analysis of 48 cross-sectional studies comparing older with younger adults, so it shows age-group differences rather than tracking individuals over time, and cannot establish that motor unit changes cause the strength loss.Review · Neurobiol Aging

   Full breakdown →Sarcopenia explained →Strength Standards →Age-related differences in motor unit behaviours and maximal strength: A systematic review and meta-analysis. Neurobiol Aging 2026
4. Physiologypreliminary · human dataAdded 29 July 2026

   Exercise blurs the line on cardiac blood tests

   A clinical review argues that exercise-induced rises in troponin and natriuretic peptides in asymptomatic athletes should be treated as mostly benign and temporary, noting that 74-96% of marathon runners exceed standard high-sensitivity troponin thresholds. The authors say sustained elevations beyond 72 hours or symptoms deserve further investigation.

   ⚠What it shows: Narrative clinical review, not a meta-analysis; the underlying literature it summarises is mostly small studies (most n<100) with short follow-up and inconsistent exercise protocols, and athlete-specific reference ranges do not yet exist.Review · Front Physiol

   Full breakdown →Left ventricular hypertrophy explained →Cardiac biomarkers in athletes and active individuals: a clinical review of exercise-induced elevations and diagnostic interpretation. Front Physiol 2026
5. Physiologypreliminary · human dataAdded 27 July 2026

   Exercise biomarker claim rests on just 10 people

   Machine-learning models classified whether serum miR-210 was raised after exercise training with 90% accuracy, but the entire study was 10 young adults, five per outcome group. Correlations between miR-210 and training frequency or age were weak and non-significant.

   ⚠What it shows: Exploratory study in just 10 young adults with five people per group, using leave-one-out cross-validation on a tiny sample: accuracy figures from samples this small are highly unstable, and the authors call the work hypothesis-generating.Study · Comb Chem High Throughput Screen

   Full breakdown →Machine Learning Classification of Serum miR-210 as a Biomarker of Exercise Training Response. Comb Chem High Throughput Screen 2026
6. Physiologypreliminary · human dataAdded 26 July 2026

   Six proteins may link BCAAs to heart disease risk

   A proteome-wide Mendelian randomisation study reports that genetically predicted branched-chain amino acid levels track with 40 circulating proteins, six of which, including PCSK9, SHBG and coagulation factor II, appear to partly mediate the link between BCAAs and ischaemic heart disease, accounting for 6.5% to 32.1% of the association. The pathways implicated involve inflammation, coagulation, lipid metabolism and cellular stress.

   ⚠What it shows: Genetic (Mendelian randomisation) analysis of existing large datasets, not a feeding trial: it uses genetic proxies for BCAA levels, not measured dietary BCAA or supplement intake, and mediation estimates rest on modelling assumptions. Findings are mechanistic hypotheses needing experimental confirmation.Study · J Nutr

   Full breakdown →Essential amino acids explained →Heart Age Calculator →Biological mechanisms underlying the cardiovascular effects of branched-chain amino acids: A proteome-wide Mendelian Randomization Study. J Nutr 2026

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