Smart pulse

Percutaneous oxygen saturation (Spo₂) was measured using a finger pulse oximeter (Smart Pulse; Fukuda Denshi, Tokyo, Japan) placed on the tip of the right forefinger. During the interval training session, the average values of the final 1 min of the last set (10 set) were calculated. During the 30-min continuous exercise session, the average values of the final 1 min of 30 min were determined. Heart rate was recorded at the same time points as the Spo₂ measurements. The subjects reported rating of perceived exertion (RPE)–respiratory strain (RPE-R) and RPE–leg strain (RPE-L) at the end of the interval training session and continuous exercise session (Wilson and Jones, 1991 (link)). Blood lactate concentrations were evaluated immediately after the interval exercise session using a lactate analyzer (Lactate Pro; Arkray Co., Kyoto, Japan). The physiological variables and the RPE during 3 consecutive days of interval and continuous exercise sessions were averaged to compare between the two trials.

Following an overnight fast, the subjects visited the laboratory in the morning and rested before the first blood collection. After a 30 min rest, a polyethylene catheter was inserted into an antecubital vein and a baseline blood sample was collected. Subsequently, respiratory gas, heart rate (HR) (Accurex Plus; Polar Electro Oy, Kempele, Finland), and percutaneous oxygen saturation (SpO₂) (Smart Pulse; Fukuda Denshi, Tokyo, Japan) were recorded. During experimental trials, blood samples were collected at baseline and at 1 h (immediately before first meal), 1.25 h, 1.5 h, 1.75 h, 2 h, 3 h, 4 h (immediately before the second meal), 4.25 h, 4.5 h, 4.75 h, 5 h, 6 h, and 7 h (14 points in total, Figure 
1). Respiratory gases were collected and analyzed using an automatic gas analyzer (AE300S, Minato Medical Science Co., Ltd, Osaka, Japan) at every hour (7 points in total). Appropriate calibrations of the O₂ and CO₂ sensors and the volume transducer were performed using calibration gases and 2 L syringe immediately before baseline measurement. From respiratory gas samples, oxygen consumption (
), carbon dioxide production (
), and ventilatory volume (
) were determined. All respiratory variables were averaged in each 3-min period. The respiratory exchange ratio (RER) was determined from the
and
measurements. HR and SpO₂ were recorded every 30 min (14 points in total).