## 1 Introduction  
Lack of sufficient time is one of the main explanations for lack of regular physical activity [1]. This problem can be solved by trying to find a relevant interval strategy that requires less time, giving many potential health benefits [2, 3, 4]. The adequate matching of an interval session is a complicated process and requires the consideration of several variables, including the intensity of the interval repetitions, their time duration, the type and duration of the interval, the number of repetitions, the number of repetitions, the number of series, and the time and intensity of the interval between series, among others [5]. Many published studies on the efficacy of interval training consist of several 30 s efforts, with the protocol based on the classic Wingate test [2, 3, 5, 6, 7, 8]. However, some find a protocol based on 30 s efforts very demanding/heavy to perform [9]. Therefore, shorter duration repetitions are suggested to reduce negative affective reactions while effectively developing both aerobic and anaerobic capacity [10, 11, 12, 13, 14, 15, 16, 17]. In order to gain an understanding of the physiological and perceptual responses to different interval programs as crucial aspects of the training cycle, studies verifying the previously mentioned modifications in a single interval session were conducted [12, 18]. [PERSON] et al. [12] verified the physiological, mechanical, and emotional effects of using the interval session of SIT\({}_{5}\) (16 \(\times\) 5 s repetitions with a 24 s interval) and SIT\({}_{20}\) (4 \(\times\) 20 s repetitions with a 120 s interval), performed in a random order on a cycloergometer, and showed that shorter efforts and shorter breaks led to a greater amplitude of changes in cardiovascular function, provoked higher exercise oxygen uptake, and the achieved higher peak power and total work performed. In contrast, respiratory exchange ratio (RER), percentage change in blood lactate concentration (diff La\({}^{-}\)), and fatigue index (FI) were higher in SIT\({}_{20}\), indicating that the SIT sessions with shorter efforts were associated with higher aerobic and anaerobic activity. [PERSON] et al. (2019) compared two interval session protocols with the same volume of work and breaks separated by a 15 min activity interval as follows: (1) 3 \(\times\) 10 s repetitions with a 30 s activity break; (2) 6 \(\times\) 10 s repetitions with a 4 min activity break. They showed higher oxygen uptake and heart rate (HR) with a lower rating of perceived exertion (RPE). SIT has been shown to be a time-efficient strategy for promoting metabolic adaptations in skeletal muscle ([PERSON] et al., 2019) while improving maximal oxygen uptake (VO\({}_{2}\)max) and peak power output ([PERSON] et al., 2019) with relatively low training effort. The selection of an appropriate load, which determines exercise intensity, is one of nine variables that modifies an interval strategy ([PERSON] et al., 2018). [PERSON] et al. (2018) used the classic SIT protocol modified load selection and applied a progression over a 6-week training process from 7.5% to 9.5% of body mass. The main goal of exercising with higher resistance is to create additional load in the involved muscles, as this additional load is considered to induce neuronal activation and greater recruitment of fast motor units ([PERSON] et al., 2019). However, to date, the optimal load in sprint interval training has not yet been established, despite hypotheses of changes in movement mechanics affecting, among other things, the time to peak power output (PPO) and the higher rotation rate of the cycloergometer flywheel. Considering these observations, the main purpose of this study was to verify changes in PPO, pH, blood lactate concentration, and oxygen uptake whilst applying a load of 7.5% and 10% of the participant's body mass in a single interval session (two series of 3 \(\times\) 10 s maximal exercise repetitions, separated by a 30 s activity break).