## 2 Materials and Methods
### Experimental Procedures  
#### 2.3.1 Familiarisation Session  
The participants attended a familiarisation session where the study procedures were explained and to screen whether the electrical stimulation of their FHB was tolerated and productive of a cramp. The FHB was selected because low frequency percutaneous stimulation of this muscle induces cramps that have both intra- and inter-sessional reliability [17; 30]. Participants were asked which leg was their dominant kicking leg. The non-dominant leg was screened for cramp induction during familiarisation, whilst the dominant leg was stimulated during testing [17]. This prevented any residual local physiological changes from the familiarisation session from affecting the results during testing, which commonly occurred the following day [17].  
During the familiarisation session, the participant sat upright on a plinth with their legs fully extended and with their ankles placed over the edge. On the non-dominant leg, two Ag/AgCl EMG electrodes were positioned 2 cm apart on the FHB mid-belly [30], and a reference electrode was placed on the ipsilateral lateral mallelous using standard EMG preparatory procedures [31] (see Figure 1). This leg was then prepared for cramp induction using electrical stimulation with a constant current stimulator (model DS7A, Digitmer Ltd., Hertfordshire, UK). The stimulation conductor was positioned inferior to the medial malleolus (Figure 1), and the tibial nerve was stimulated sub-maximally 2-4 times with a 1 ms electrical stimulus at 200 mA. The site that stimulated the greatest hallux flexion was marked for replication during cramp induction. The EMG electrodes were then connected to a computer via a Bortec AMT-8 EMG amplifier (Bortec Biomedical Ltd., Calgary, AB, Canada) and an NI USB-6221 analogue to digital converter (National Instruments, Austin, TX, USA), which began recording the time and EMG from the initiation of the electrical stimulus using the LabView software package (National Instruments, Austin, TX, USA).  
The participant was shown how to perform an isometric contraction of the non-dominant FHB and was allowed time to practice. Once able, they were instructed to repeat and maintain the contraction until signaled to relax, and were told to indicate when they felt the muscle was about to cramp. When the impending cramp was signaled, a train of electrical stimulation via the tibial nerve was delivered at an intensity of 200 mA for 2 s. The volitional contraction was maintained for 10 s from stimulus initiation, and then the participant was instructed to relax. The initial stimulus frequency was 4 Hz, and a total of eight stimuli were delivered during the first trial [30]. If a cramp was not induced,the participant rested for 1 min, and the process was repeated with the train frequency increased by 2 Hz [30]. This process was repeated until either an EIMC of the FHB was produced or until the frequency reached 24 Hz [30]. The frequency at which a cramp was induced was recorded as the participant's cramp threshold frequency (CTF), which is the minimum frequency required to stimulate a cramp [32]. This CTF was used to induce all subsequent cramps.  
The FHB was considered to be cramping if involuntarily contraction immediately succeeded the cessation of volitional contraction, which was verified by the participant's self-report of a cramp, sustained hallux flexion, and an average EMG root mean square amplitude >2 SDs greater than the baseline reading [30]. Upon determining the CTF, the protocols for ingesting and mouth rinsing were practiced with water, thus ensuring protocol familiarity prior to experimental sessions.