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Creatine Monohydrate – LO6a Structure & Synthesis
Creatine is a nitrogen‑containing compound synthesized from glycine, arginine and methionine in the liver, kidneys and pancreas; in muscle it is phosphorylated to phosphocreatine (PCr), a high‑energy phosphate store.
Creatine Monohydrate – LO6b Sources & Normal Function
Dietary sources include meat and fish; vegetarians have lower muscle creatine stores. In skeletal muscle, creatine and phosphocreatine buffer ATP during short, intense efforts by donating phosphate to ADP via creatine kinase.
Creatine Monohydrate – LO6c ‘Safe’ Intake (non‑sport)
Typical supplemental protocol is a 5–7 day loading phase of ~0.3 g/kg/day (about 20 g/day), followed by 3–5 g/day maintenance; long‑term use at these doses appears safe in healthy individuals with normal kidney function.
Creatine Monohydrate – LO6d Drug Test Value in Sport
Creatine is a legal nutritional supplement and is not on the WADA Prohibited List or monitored by the Athlete Biological Passport.
Creatine Monohydrate – LO6e EA Intake & Risks in Sport Settings
Loading 20 g/day for 5–7 days then 3–5 g/day maintenance is common. Side‑effects can include weight gain from water retention, GI upset and, rarely, muscle cramping; no strong evidence of kidney damage in healthy users at recommended doses.
Creatine Monohydrate – LO6f Rationale & Purported Mechanism in Sport
By increasing intramuscular creatine and PCr stores, supplementation enhances rapid ATP resynthesis during repeated maximal efforts (≤30 s), improving power output, strength and the ability to perform repeated sprints; most relevant for resistance/power and whole‑body sprint activities.
Creatine Monohydrate – LO6g Research Evidence
Hundreds of studies show that creatine reliably increases total and phosphocreatine in muscle and improves maximal strength, repeated sprint performance and lean mass gains when combined with resistance training; effects on pure endurance events are minimal.
Caffeine – LO6a Structure & Synthesis
Caffeine is a methylxanthine alkaloid (1,3,7‑trimethylxanthine) occurring naturally in coffee beans, tea leaves, cacao and some other plants; it can also be synthesized industrially.
Caffeine – LO6b Sources & Normal Function
Common sources are coffee, tea, cola beverages, energy drinks, chocolate and medications. It acts as a central nervous system stimulant by antagonizing adenosine receptors, increasing alertness and reducing perceived fatigue; it also influences catecholamines and calcium handling in muscle.
Caffeine – LO6c ‘Safe’ Intake (non‑sport)
For most healthy adults, up to about 400 mg/day (≈3–5 mg/kg) is considered a safe chronic intake; higher doses increase side‑effects such as jitteriness, insomnia and palpitations.
Caffeine – LO6d Drug Test Value in Sport
Caffeine was removed from the WADA Prohibited List but is on the Monitoring Program; high urinary concentrations may be flagged, but its use is currently permitted in competition.
Caffeine – LO6e EA Intake & Risks in Sport Settings
Ergogenic doses are typically 3–6 mg/kg body mass taken ~30–60 min before exercise. Side‑effects include increased heart rate and blood pressure, anxiety, tremor, GI upset, sleep disturbance and, at very high doses, arrhythmias.
Caffeine – LO6f Rationale & Purported Mechanism in Sport
Caffeine blocks adenosine receptors, reducing perception of effort and pain, increases central drive, and may enhance Ca2+ release and Na+/K+ ATPase activity in muscle; at moderate doses it can also increase fat oxidation and spare glycogen. It is ergogenic for endurance, high‑intensity intermittent and even some strength/power tasks.
Caffeine – LO6g Research Evidence
Numerous meta‑analyses show that 3–6 mg/kg caffeine improves time‑trial performance by a few percent, increases time‑to‑exhaustion in endurance tests, and can enhance repeated sprint performance; responses are individually variable and influenced by habitual use and genetics.
L‑Carnitine – LO6a Structure & Synthesis
L‑Carnitine is a quaternary ammonium compound synthesized from lysine and methionine, mainly in liver and kidney, and stored in skeletal and cardiac muscle.
L‑Carnitine – LO6b Sources & Normal Function
Rich in red meat and dairy; small amounts come from other foods and supplements. Carnitine shuttles long‑chain fatty acids into mitochondria via the carnitine palmitoyltransferase system for β‑oxidation, and also participates in removal of acyl groups from mitochondria.
L‑Carnitine – LO6c ‘Safe’ Intake (non‑sport)
Typical supplemental intakes are 1–3 g/day; these appear safe for most healthy adults, though very high doses can cause GI upset and fishy body odor from trimethylamine production.
L‑Carnitine – LO6d Drug Test Value in Sport
L‑Carnitine is not prohibited by WADA. However, some methods of intravenous administration at high volumes can violate anti‑doping rules related to IV infusions.
L‑Carnitine – LO6e EA Intake & Risks in Sport Settings
EA protocols often use 2–3 g/day orally for weeks to months. Oral bioavailability is limited, and excess can cause nausea, vomiting, cramps and diarrhea, plus potential fishy odor from gut microbial metabolism.
L‑Carnitine – LO6f Rationale & Purported Mechanism in Sport
Carnitine is marketed to enhance fat oxidation, spare glycogen and improve endurance by increasing muscle carnitine content and facilitating fatty‑acid transport into mitochondria; some claims also suggest reduced lactate accumulation and better recovery.
L‑Carnitine – LO6g Research Evidence
Most studies show little or no change in muscle carnitine content or endurance performance with standard oral doses; a few long‑term, high‑carbohydrate co‑ingestion studies report modest benefits, but overall the evidence for robust ergogenic effects is weak.
Ketone Supplements – LO6a Structure & Synthesis
Nutritional ketone products typically contain β‑hydroxybutyrate (BHB) as ketone salts or esters; endogenously, BHB and acetoacetate are produced in the liver from fatty acids during low‑carbohydrate intake or prolonged exercise.
Ketone Supplements – LO6b Sources & Normal Function
Normally, ketone bodies are synthesized in the liver and used by the brain, heart and skeletal muscle as alternative fuels when carbohydrate availability is low. Supplements provide exogenous ketones without the need for prolonged fasting or ketogenic diets.
