Exercise is a metabolic event that creates profound, acute demands on the body's energy substrates, structural proteins, and hormonal regulatory systems. Nutrition — both before and after training — directly shapes the biochemical environment in which exercise occurs and recovery unfolds. Understanding the mechanistic basis of nutrient timing and macronutrient composition around workouts allows athletes and active individuals to strategically support performance and adaptation.
Glycogen: Fuel, Depletion and Resynthesis
Skeletal muscle stores approximately 300–500 g of glycogen (1,200–2,000 kcal), with the liver storing an additional 80–100 g (320–400 kcal). During moderate-to-high-intensity aerobic exercise, muscle glycogen is the predominant fuel — glycolysis converts glucose-1-phosphate (released from glycogen by glycogen phosphorylase) into ATP. Glycogen stores in working muscle are substantially depleted after approximately 60–90 minutes of continuous moderate-to-high-intensity exercise, and progressive glycogen depletion is associated with reduced exercise intensity, increased muscle protein catabolism, and impaired post-exercise recovery.
Pre-workout carbohydrate loading (consuming 1–4 g of carbohydrate per kg body weight 1–4 hours before exercise) ensures that muscle and hepatic glycogen stores are topped up before the metabolic demand begins. High-GI carbohydrates (e.g., white rice, bread, sports drinks) consumed 30–60 minutes before training rapidly elevate blood glucose and insulin, facilitating glycogen synthesis. Lower-GI sources consumed 2–3 hours before exercise provide a more sustained glucose supply without the insulin rebound that can cause transient hypoglycaemia near the start of exercise.
Post-exercise glycogen resynthesis follows a biphasic pattern: an initial rapid phase (0–30 minutes post-exercise) characterised by insulin-independent GLUT4 translocation driven by muscle contraction-mediated signalling (AMPK activation), and a slower insulin-dependent phase lasting several hours. Consuming carbohydrates (0.8–1.2 g/kg) immediately post-exercise maximises the rate of glycogen resynthesis during the rapid phase, with co-ingestion of protein (0.2–0.4 g/kg) further accelerating resynthesis by stimulating insulin secretion.
Muscle Protein Synthesis: The Anabolic Window
Resistance exercise creates microdamage to myofibrils and simultaneously activates the mTORC1 signalling cascade — particularly through the mechanistic target of rapamycin complex 1 (mTORC1), activated by both mechanical loading and amino acid availability (particularly leucine). mTORC1 phosphorylates p70S6K1 and 4E-BP1, downstream targets that promote the initiation of mRNA translation and ribosome biogenesis, increasing the rate of muscle protein synthesis (MPS).
The anabolic window — the period immediately following exercise during which MPS is most responsive to protein ingestion — is most acute in the first 30–60 minutes post-exercise, though the elevated MPS response extends for up to 24–48 hours. Consuming 20–40 g of high-quality protein (rich in leucine, ideally >2.5 g leucine per dose) within this window maximises the MPS response per gram of protein. Distributing protein intake evenly across 3–5 meals throughout the day, rather than concentrating it in one sitting, provides the most consistent MPS stimulation, since the leucine-mediated mTORC1 signal is subject to a refractory period of approximately 3–5 hours between meals.
Electrolyte Physiology During Exercise
Sweat is not pure water — it contains significant concentrations of sodium (20–80 mmol/L), chloride (16–60 mmol/L), potassium (4–8 mmol/L), and small amounts of magnesium and calcium. Sweat rate during exercise varies from 0.5 to 2.5 L/hour depending on exercise intensity, ambient temperature, and individual sweat rate genetics. Sodium loss is the most physiologically significant: hyponatraemia (serum sodium below 135 mmol/L) caused by excess water intake without sodium replacement impairs nerve conduction and muscle function more acutely than dehydration alone.
Potassium plays a critical role in action potential repolarisation in muscle cells: the Na⁺/K⁺-ATPase pump restores the resting membrane potential after each action potential by pumping 3 Na⁺ out and 2 K⁺ in per ATP hydrolysed. High-intensity exercise depletes intracellular K⁺ stores progressively, contributing to muscle fatigue via altered membrane excitability. Post-exercise potassium replacement from dietary sources (bananas, sweet potatoes, legumes) or electrolyte supplements restores membrane potential and accelerates recovery.
Adaptogens and the HPA Axis Under Physical Stress
Intense exercise is a physiological stressor that activates the hypothalamic-pituitary-adrenal (HPA) axis: the hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the anterior pituitary to secrete ACTH, which in turn triggers the adrenal cortex to release cortisol. Cortisol mobilises energy substrates (stimulates gluconeogenesis, inhibits protein synthesis, promotes lipolysis) and has anti-inflammatory effects that are appropriate in the acute post-exercise context. However, chronically elevated cortisol — caused by overtraining without adequate recovery — suppresses mTORC1 signalling via REDD1 upregulation, impairing the anabolic response to training.
Ashwagandha (Withania somnifera) root extract contains withanolides — steroidal lactones including withaferin A and withanolide D — that modulate HPA axis activity. The proposed mechanism involves withanolide binding to glucocorticoid receptors and nuclear factor kappa B (NF-κB), modulating the sensitivity of the hypothalamic stress response. Our Ashwagandha supplement provides a standardised withanolide extract (KSM-66 or equivalent), the form used in clinical trials examining its effects on exercise recovery and HPA axis markers.
Omega-3 EPA and DHA are incorporated into the phospholipid bilayer of muscle cell membranes. Higher membrane DHA content increases membrane fluidity and GLUT4 transporter mobility, potentially facilitating post-exercise glucose uptake. EPA is a precursor to anti-inflammatory eicosanoids (PGE₃, LTB₅) that resolve the acute inflammatory phase following muscle damage more efficiently than arachidonic acid-derived prostaglandins. Our Omega-3 Fish Oil supplement supplies pre-formed EPA and DHA for direct incorporation into muscle membranes.
Maca root (Lepidium meyenii) provides a dense matrix of amino acids, glucosinolates (benzylglucosinolate, 4-methoxybenzylglucosinolate), macamides, and adaptogenic alkaloids. Traditionally used at altitude in the Andes for sustained energy and endurance, maca contributes glutamine (important for muscle recovery and intestinal integrity during heavy training) and arginine (a nitric oxide precursor affecting vasodilation and muscle blood flow). Our Maca Root supplement provides a concentrated root powder.
Recent Research
- Ivy (2004) — Journal of Exercise Science & Fitness — Characterised the biphasic muscle glycogen resynthesis response post-exercise; demonstrated that carbohydrate consumption within 30 minutes of exercise cessation restores glycogen at rates 2–3× faster than delaying intake by two hours, due to the transient insulin-independent GLUT4 upregulation driven by AMPK and CaMKII signalling.
- Moore et al. (2009) — American Journal of Clinical Nutrition — Dose-response study of protein ingestion and muscle protein synthesis in young men; determined that 20 g of egg protein maximally stimulated MPS after resistance exercise, with higher doses oxidising excess amino acids rather than incrementally increasing MPS, establishing the protein-per-meal optimum for practical nutrition planning.
- Wankhede et al. (2015) — Journal of the International Society of Sports Nutrition — Randomised, double-blind, placebo-controlled trial of KSM-66 ashwagandha (300 mg twice daily, 8 weeks) in male subjects undergoing resistance training; reported significant improvements in muscle strength (bench press and leg extension), muscle recovery as measured by creatine kinase levels, and testosterone concentrations compared to placebo.
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