Evaluating the Effect of Hydrogel Encapsulated Sodium Bicarbonate on Exercise Tolerance in Healthy Adults

INTERVENTION: The research comprises a randomised double‐blind placebo‐controlled trial to evaluate the safety, tolerability, and physiological effects of a hydrogel‐encapsulated sodium bicarbonate formulation co‐delivered with caffeine and carbohydrates. The study seeks to establish whether this intervention improves exercise tolerance and mitigates symptoms of fatigue. Phase 1 will involve 16 healthy adults (8 per intervention and control group). Participants will complete two test visits at the laboratory in the Flinders University Health and Medicine Research building. During the first visit participants will undertake a cycling based exercise test (INSCYD lactate test) to define baseline exercise tolerance. During the second visit, 96 hours later, they will orally ingest either an active hydrogel formulation containing 0.25 g/kg of body mass of sodium bicarbonate (90 min pre‐exercise), as well as 100 mg caffeine and 25 g of carbohydrate (45 min pre‐exercise) before undertaking the same INSCYD lactate test. To ensure adherence, treatment ingestion will occur under researcher supervision. Physiological responses will be assessed using capillary lactate sampling, venous blood gas analysis, and subjective effort ratings. Tolerability will be evaluated using gastrointestinal distress symptom questionnaires, palatability scores, and protocol adherence. CONDITION: Musculoskeletal ‐ Normal musculoskeletal and cartilage development and function Physical fatigue; ; Physical fatigue PRIMARY OUTCOME: Exercise tolerance[Capillary blood lactate concentration during the INSCYD cycling lactate test; ; Maximal 4‐minute mean power output (W) during the final maximal effort; ; Rating of Perceived exertion Baseline (pre‐intervention), each stage of the INSCYD protocol and post‐exercise.; ; Post‐intervention (single acute dose; assessed during the exercise test conducted 90 minutes after hydrogel ingestion); ; Following each stage of the INSCYD lactate protocol.] Supplement safety[‐ Gastrointestinal symptoms: Participants will rate the severity (0–10 numeric rating scale) and duration of common gastrointestinal symptoms (nausea, bloating, cramping, flatulence, reflux/heartburn) using a study‐specific questionnaire administered immediately post‐exercise and at 72 hours post‐trial.; ; Adverse event monitoring: All adverse events (AEs) will be monitored from supplement ingestion until 72 hours post‐trial. During laboratory visits, participants will be directly supervised by study investigators, and any signs or symptoms observed by research staff will be documented contemporaneously. Participants will also be specifically asked about any new or worsening symptoms at predefined timepoints (immediately post‐exercise and 72 hours post‐trial). Following discharge from the laboratory, participants will self‐monitor and report any AEs via structured follow‐up questionnaires and direct email/telephone contact with the research team. ; An adverse event will be defined as any unfavourable or unintended sign or symptom temporally associated with study participation, whether or not considered related to the intervention. ; Serious adverse events (SAEs) will be defined according to ICH‐GCP criteria and will be reported to the relevant ethics committee in accordance with institutional guidelines. Immediately post‐exercise and 72 h post session.] SECONDARY OUTCOME: Acid–base balance and buffering capacity (assessed as a composite outcome).[Venous blood gas (VBG) analysis ; ‐ pH ; ‐ Bicarbonate ; ‐ Base excess (BE) ; ‐ pCO2, ; ‐ Electrolytes (Na+, Ca++, K+, Cl‐) Baseline (pre‐ingestion) ; ; Pre‐exercise ; ; Immediately post‐exercise] Lactate kinetics and metabolic profile (assessed as a composite outcome)[Capillary blood lactate sampling ; ; INSCYD metabolic modelling outputs, including: ; ; Lactate thresholds (LT1, LT2) ; ; Maximal lactate steady state (MLSS) ; ; VLaMa X; ; Modelled VO2ma X; ; Substrate utilisation During exercise testing (submaximal stages and maximal effort) ; ; Recovery period post‐exercise] Perceived exertion during exercise[Borg Rating of Perceived Exertion (RPE) At the end of each exercise stage ; ; At exercise termination] Supplement tolerability[Gastrointestinal symptom questionnaire (Likert‐scale severity ratings) and palatability visual analogue scale (VAS) assessed as a composite outcome. Post‐exercise (same visit) ; ; 72‐hour follow‐up] INCLUSION CRITERIA: Participants must meet all of the following criteria: 1. Aged over 18 to under 65 years. 2. Body mass inde X(BMI) between 18–30 kg/m². 3. Recreationally active, defined as participating in structured physical activity at least twice per week. 4. Able and willing to provide written informed consent. 5. Able to attend all scheduled study visits and comply with study procedures.