What is it?
- Quinine is a bitter alkaloid sourced from the bark of the cinchona tree1 and has a long history of use in traditional medicine such as a treatment for malaria2, where doses of 1 g of quinine sulphate were administered before the acute phase.3
- Quinine carries a strong bitter taste4 and is used in tonic water as a flavouring agent.1 Its concentration in commercial beverages varies greatly and such products typically lack nutritional information detailing the amount of quinine used. The concentration of quinine in tonic water is much lower than that used for medical purposes.
- Quinine is one of the latest emerging acute nutritional strategies that purportedly activate brain areas to reduce perception of effort and subsequent pacing decisions, in both research and practical settings.5
- Ingestion of Quinine activates the bitter taste receptors in the oral cavity and upper gastrointestinal tract to increase corticomotor excitability and stimulate neural excitability.4 Changes in the autonomic nervous system (ANS)6,7 provide a potential mechanism to enhance performance in high effort, short duration activities.
- Unlike the case for carbohydrate mouth rinsing, the quinine solution needs to be swallowed for it to prove effective4 and to ensure that it has contact with specific receptors that are concentrated in the back of the mouth and throat.
- Benefits of quinine ingestion as a sensory-driven tastant include increased 30 second cycling sprint performance by 2.5-4%8 and increased cycling performance (~6%) during initial stages of a 3 to 4-minute cycling effort.9
- Since the effects of quinine ingestion are seen immediately after the ingestion of quinine, the ergogenic effect has been attributed to central activation by afferent taste.
- To date, studies that have reported benefits of quinine ingestion have involved exercise protocols undertaken on cycle ergometers. It is unclear if this translates to real world cycling (e.g. track cycling) and whether other sprint events in running or swimming would benefit from pre-event quinine ingestion.
- It is unclear whether other factors might inhibit or diminish sensory-driven pathways when ingesting quinine. For example, bitter tasting medications are often masked by manipulations involving salt.10 Therefore, it might be possible to counter-act an unpleasant and persistent bitter taste after the event by ingesting a salty snack. However, whether salt intake prior to or around the pre-event quinine ingestion interferes with any ergogenic effect is unknown.
- It is also relevant to explore ways to amplify sensitivity to the bitter taste prior to ingesting quinine to magnify performance benefits without needing to increase the actual dose.