For session 1, subjects reported to the testing laboratory to initiate the testing procedure. After signing an informed consent, participants completed a health history questionnaire (HHQ) and physical activity questionnaire (PAQ). Participants who reported cardiometabolic diseases or musculoskeletal diseases were excluded, as well as individuals who reported having any musculoskeletal injury within the 6-month period prior to the study. Additionally, participants who self-reported using ergogenic supplements or prescribed medication impacting cardiometabolic function were also excluded from the study.
Upon completion and review of the HHQ and PAQ, participant’s height, weight, and body composition measurements were obtained via standard techniques. Height was obtained using a stadiometer (SECA model 769, Hamburg, Germany) and weight and body composition were collected via bioelectrical impedance analysis (InBody 720; Seoul, South Korea), according to manufacturer’s directions.
For session 2, 3, and 4, subjects were instructed to report to the testing laboratory for each session. Participants were tested in pairs in order to assist in maintaining the cadence of the exercise routine and to provide an additive motivation(24, 25). Subjects were instructed to arrive in an 8-hour fasted state, and this status was confirmed upon arrival. Testing protocols commenced once both subjects were present in the lab and were verified for participation.
Upon arrival at the lab the participants were asked to complete a State Anxiety Inventory (SAI)(26) and the Profile of Mood States (POMS)(27) questionnaires and were then provided with either the control (flavored water), placebo (CaCO3 and flavoring), or NaHCO3 supplement (and flavoring) beverage. All three beverages consisted of 296 ml of water and 2 ml of a liquid flavoring compound containing water, malic acid, propylene glycol, citric acid, sucralose, acesulfame potassium, potassium citrate, red 40, and potassium sorbate, with the placebo beverage also containing 0.30g•kg− 1 body weight of CaCO3, and the experimental beverage containing 0.15g • kg− 1 body weight NaHCO3.
Testing session 2 (control, flavored water) occurred first for all subjects, with sessions 3 and 4 being randomized for the placebo (CaCO3 and flavoring), or NaHCO3 (and flavoring) supplement beverage amongst participants using double-blinded methods. Participants were allowed five-minutes within which to complete drinking the beverage, and all subjects in the study were able to comply with this requirement.
After ingesting the designated beverage for the test day, participants were asked to sit quietly for 35-minutes before they were escorted to the testing area and reminded of the exercise protocol. Measures of heart rate (HR), BLa, and RPE were collected immediately prior to commencement of the exercise protocol (0 min), and again at 5 min, 10 min, and 15 min during exercise, and immediately upon cessation of exercise (20 min) for a total of 5 measurements during each protocol (see Fig. 1). All measures were collected near simultaneously, with each participant having a researcher dedicated to their respective data collection. Timing was controlled using a Macromedia Authorware (v.5) program written specifically for the protocol.
Once the pre-exercise measurements (HR, BLa, RPE) were obtained for both participants, the subjects were instructed to begin the exercise protocol. The exercise protocol began with step-ups onto a 30.5-cm platform using a metronome setting of 60 beeps per minute (BPM) to maintain the tempo. After two minutes and thirty seconds (2.5 min) subjects switched to jumping jacks in which their hands touched above their heads at one beep, and down to their sides for the next beep, repeating the movements until the 5-min mark. The participants followed this procedure until they were instructed to stop and sit down to obtain HR, BLa, and RPE measurements at the respective data collection time points (5 min, 10 min, and 15 min). The metronome setting increased after each stoppage for measurements to 70 bpm and 80 bpm, respectively. The step-ups and jumping-jack cycle continued until the 15-min measurement. Once the measurements were obtained at the 15-min timepoint, subjects were instructed to perform a modified burpee at a cadence of 90 bpm for the final 5-min. The exercise protocol ended at either at the conclusion of 20-min of cadenced exercise or when the subject could no longer keep pace with the metronome for greater than three repetitions. The final measurements were collected immediately upon the cessation of exercise.
To assess BLa, researchers utilized a single-use lancet device to puncture the skin just off the center of a fingertip pad utilizing aseptic techniques. The first flow of blood was wiped away with a cotton swab, and then approximately 5µL (2mm) of blood was loaded on the lactate strip and immediately analyzed using the Lactate Plus meter (Nova Biomedical, Waltham, MA). HR was collected using Polar heart rate monitor (model FT1, Polar Electro Oy, 2014) and RPE was measured using the 6–20 Borg Rating Scale(28) which was projected onto a wall in front of the participants.
Upon completion of the exercise protocol and collection of BLa, HR, and RPE measures, participants were asked to complete the SAI and POMS once again and were also asked to evaluate the beverage they had ingested for taste and GI distress. After these tasks were completed, participants could depart the lab.
Subjects reported to the testing laboratory a week later to repeat the protocol for testing session 3 which was randomized for the placebo (CaCO3 and flavoring) and NaHCO3 (and flavoring) supplement beverage treatments. Session 4 took place another week later and all exercise protocols and testing protocols remained consistent, the only change between session 3 and 4 was the beverage provided.