The Effect of Acute Caffeine and Sodium Bicarbonate Supplementation on Upper and Lower Submaximal Resistance Training Performance

The study will employ a randomized, double-blind, placebo-controlled, cross-over study design that examines the effect of caffeine and sodium bicarbonate on knee extension and bench press performance. Parameters include peak isoinertial force (1 repetition maximum: 1RM), rate of force development, movement velocity, number of repetitions to failure with a 10 repetition maximum (10RM) load, and electromyography (EMG) activity. The participants will complete three separate visits to the laboratory (1. placebo, 2. caffeine, and 3. sodium bicarbonate ingestion). With respect to the first visit, participants will sign a consent form and complete a health history questionnaire. Their respective anthropometric measurements will be taken, including height, weight, body mass index (BMI). Participants will then be introduced to the rate of perceived exertion scale for use during the trials. Blood lactate (Lactate Pro, Arkray, Kyoto, Japan) levels will be collected and analyzed from the index finger of the tested arm. Researchers will establish the 1RM for the bench press (upper-body) and knee extension (lower-body) exercises. The participants will complete a warm-up set of 8-10 repetitions at 50% of their body mass, followed by a 60-second rest period. The participants will then complete a second warm-up set of 3-5 repetitions with a 5-10 kg increase from the initial set, followed by another 60-second rest interval. the participants will then complete 2-3 repetitions with an additional 5-10 kg increase, followed by a rest for an additional 120 seconds. Each subsequent one-repetition attempt increased an additional 5-10 kg, followed by a 120-second rest period. The final attempt will be determined by repeating the steps illustrated above until the participants can no longer complete a single unassisted repetition with additional weight. This value will then be illustrated as the participant's 1RM and will be utilized to calculate exercise intensity for the two subsequent supplementation trials.

All testing will be performed within the laboratory. Participants are instructed to meet the following conditions 24-h before each experimental trial: (i) to avoid vigorous exercise, (ii) to adopt a similar diet and drink intake, (iii) to refrain from the consumption of alcohol, caffeine, and other stimulants.

Measures

For the knee extension measures, EMG activity will be collected from the mid-belly (midway between the anterior superior iliac spine to the superior edge of the patella) of the vastus lateralis and biceps femoris (midway between the gluteal fold and the popliteal space) of the non-dominant leg. Before participants perform the bench press, surface EMG recording electrodes will be placed approximately 3 cm apart over the proximal, lateral segment of the biceps brachii and over the lateral head of the triceps brachii. The distance of the biceps brachii electrodes from the acromion process and the distance of the triceps electrodes from the biceps electrodes will be recorded to ensure accurate replacement for subsequent tests. A thorough skin preparation for all electrodes will include shaving and removal of dead epithelial cells with abrasive pad around the designated areas, followed by cleansing with an isopropyl alcohol swab. EMG will be collected using a Biopac (Biopac Systems Inc.) data acquisition system at a sample rate of 2,000 Hz [impedance = 2 MΩ, common mode rejection ratio >110 dB min (50/60 Hz), noise >5 μV]. A bandpass filter (10-500 Hz) will be applied prior to digital conversion.

The root mean square (RMS) EMG will be monitored throughout the range of movements for both the bench press and knee extension. The mean RMS EMG will be normalized to the highest pre-test value and reported as a percentage.