Achieving the highest level of performance in any sport is a gradual and comprehensive endeavor that extends over multiple years (Alejo et al., 2022), requiring continuous improvement of sport-specific characteristics from a junior level, progressing to under 23 (U23), and ultimately getting the professional level. Physiological attributes, anthropometric variables, bio-motor abilities, and body composition parameters affecting sprint kayaking performance have already been well elucidated (Fry and Morton, 1991; Byrnes and Kearney, 1997; Bishop, 2000; van Someren and Palmer, 2003; van Someren and Howatson, 2008; Michael et al., 2009; Buglione et al., 2011; McKean and Burkett, 2014; Borges et al., 2015; Hamano et al., 2015; López-Plaza et al., 2017; Paquette et al., 2018; Pickett et al., 2018; Coleho et al., 2020; Kukic et al., 2022; Gäbler et al., 2023). However, the information regarding the difference between age categories and expertise levels is limited. Understanding the actual physiological and performance disparities among athletes of various age groups and expertise levels could help to identify particular attributes that need to be developed from younger ages to professional levels to enhance the likelihood of achieving high-level performance (Sheykhlouvand et al., 2015; Foster et al., 2022).

Sprint kayak is an Olympic event on a flat-water course with official races in World championships set over four distances of 200-m (∼38 s), 500-m (∼100 s), 1,000-m (∼220 s), and 5,000-m (∼1,290 s) for men senior category (International Canoe Federation) ¹ . Races are completed individually and in crews of up to four. Kayakers compete in a seated position, propelling themselves forward using a double-blade paddle. Research indicates that sprint kayak performance mainly depends on upper-body anaerobic and aerobic power (Borges et al., 2015; López-Plaza et al., 2017; Barzegar et al., 2021; Sheykhlouvand et al., 2022). For instance, “using the accumulated oxygen deficit method, the contribution of aerobic metabolism to different distances in highly-trained kayakers has been estimated at 37%, 64%–78%, and 85%–87% for 200-m, 500-m, and 1,000-m, respectively (Byrnes and Kearney, 1997; Zamparo et al., 1999; Zouhla et al., 2012)”. Middle-distance events (500-m and 1,000-m) kayak sprint performance is strongly correlated to maximum oxygen uptake (VO_2max) and lactate threshold (Zamparo et al., 1999; Paquette et al., 2018). By contrast, short-distance 200-m performance is not related to VO_2max and lactate threshold but upper-body anaerobic power/capacity, distinguishing international-level kayakers from national-level athletes (van Someren and Palmer, 2003).

Enhanced upper-body strength and muscular endurance also significantly determine sprint performance (Forbes and Sheykhlouvand, 2016; Sheykhlouvand et al., 2022). Enhancing the pulling motion during paddling strokes leads to a steady augmentation of the force during the entire pulling phase, resulting in better speed maintenance (Ualí et al., 2012; McKean and Burkett, 2014). Kayakers must generate considerable average power during each stroke and apply significant forces on the blade of the paddle while propelling forward to achieve the highest average boat velocity (Michael et al., 2009; Kukić et al., 2022). Muscle mass significantly affects force outcomes per paddling stroke (Kukić et al., 2022). Also, higher body fatness increases the drag force and reduces the paddling efficacy (Michael et al., 2009; McDonnell et al., 2012). Hence, when planning long-, medium- and short-term training, it is crucial to consider the body composition of sprint kayakers (Borges et al., 2015).

Although previous studies have identified various contributing attributes to sprint kayak performance, reviewing the literature indicates that no previous study has directly compared these parameters among sprint kayakers of varying age groups and expertise levels. Accordingly, this study aimed to compare cardiorespiratory fitness, bio-motor abilities, and body composition indicators among sprint kayakers of different age groups (junior, U23, professional) and expertise levels (international-level vs. club-level). We hypothesized the presence of a linear progression from junior to professional levels for the specified variables. Additionally, individuals competing at the international level will exhibit superior physiological and performance capabilities compared to sprint kayakers participating at the club level.

Tables 1–6 represent the difference between age groups and expertise levels for aerobic fitness, 500- and 1,000-m paddling performance, strength and power, and body composition indicators.

The most striking findings of this study were that U23 athletes, especially professional sprint kayakers, displayed significant variations in cardiorespiratory fitness indicators (e.g., VO_2max, vVO_2max, VO₂/HR, V_E) and paddling performance, compared to junior athletes. However, no disparities were observed in major indicators like VO_2max when comparing U23 athletes and professional sprint kayakers. There were evident strength and power differences between professionals and the other two categories, consisting of relative and absolute PPO, APO, and 1RM in BP, PBP, and CR. Professional athletes also displayed lower body fat and higher muscle mass than juniors and U23 athletes. Athletes competing at the international level exhibited superior aerobic power, bio-motor abilities, and paddling performance compared to their club-level counterparts. Results revealed a significant contrast in body composition indicators, with international-level athletes displaying lower body fat and higher muscle mass.

Cardiorespiratory fitness indicators have been widely used as determinants of sprint kayak performance (Borges et al., 2015; Paquette et al., 2018; Sheykhlouvand et al., 2022; Du and Tao, 2023). In addition to 500 and 1,000-m TT, most of the assessed cardiorespiratory fitness parameters had different values between junior kayakers and the other age groups. Still, only some variables, such as VT₁ (but not VO_2max), varied between U23 and professional sprint kayakers. Research has indicated that, by accounting for ∼79% variance in 500-m paddling time, anaerobic threshold is considered an effective factor on 500-m TT (Bishop, 2000). The significance of the lactate threshold (Winchcombe et al., 2019) and ventilatory threshold (Michael et al., 2009) in paddling performance has been emphasized by additional research, with the proportion of anaerobic energy metabolism contribution changing based on the distance. However, no linear continuity (i.e., elevation from junior to professional levels) was found for %VO_2max at which VT₁ and VT₂ occurred. A proportion of VO_2max that an athlete can maintain for a specified time has traditionally been considered a measure of endurance (Billat, 1996; Joyner and Coyle, 2008). Research controversially indicates that trained athletes may exhibit a ventilatory threshold (overall equivalent to lactate thresholds) at a higher percentage of VO_2max compared to untrained individuals (Alejo et al., 2022). In the present study, we found no difference for VT₂ between age categories, but professionals attained a higher percentage of VO_2max at VT₁ than junior and U23 kayakers. However, when assessing endurance performance, it is recommended not to rely solely on this parameter to predict endurance performance accurately. Instead, it should be used with other factors, like vVO_2max or peak power output (Støa et al., 2020).

In longer distances (i.e., 1,000-m) also, aerobic power (indicated by VO_2max) plays a vital role in successful performance (Michael et al., 2009; Zouhla et al., 2012). Regardless of the distance covered (500 or 1,000-m), the anaerobic pathway is the primary energy source at the start of the race, but it decreases and becomes almost exclusively aerobic toward the end (Zouhla et al., 2012). However, the contribution of aerobic metabolism during 1,000-m races is significantly greater than that of 500-m kayaking events (Fry and Morton, 1991; Zouhla et al., 2012; Paquette et al., 2018). Beyond the magnitude of aerobic and anaerobic contribution, the capacity of muscle to extract O₂, which is independent of VO_2max, is considered a more vital determinant of performance (Paquette et al., 2018). It is generally accepted that VO_2max is determined by O₂ delivery (i.e., central component) and O₂ extraction by the active muscles (i.e., central component) (Sheykhlouvand et al., 2022; Paquette et al., 2018 indicated that muscle capacity to extract O₂ strongly influences paddling performance and could be considered better predictor of performance than VO_2max in sprint kayakers. In this study, we have not evaluated muscle oxygenation, and we cannot speculate in this regard, but O₂ extraction, could be considered an effective part of the peripheral component of aerobic fitness, affecting sprint kayak performance (Paquette et al., 2018).

Contrary to aerobic fitness, strength and power showed a remarkable difference between U23 and professionals, making them a more sensitive performance marker than VO_2max. The importance of muscular strength and power production in kayaking performance has already been well-established (Michael et al., 2009; McKean and Burkett, 2014; Pickett et al., 2018). To optimize the average velocity of the boat and sprint performance, the athlete needs to generate considerable average power during each stroke and apply substantial average forces to the paddle blade while propelling forward (Messias et al., 2018; Kukic et al., 2022). Improved sprint kayak performance could be facilitated through an increase in the power-to-weight ratio of the athlete and a decrease in opposing drag forces imposed by air and water (Michael et al., 2009; McKean and Burkett, 2014). Standard and well-designed boats also can decrease both aerodynamic and hydrodynamic forces on the kayak and facilitate the movement of the kayak through the water (McKenzie and Berglund, 2019).

In line with the mentioned findings, we found a significantly different power-to-weight ratio between professionals and other age groups and U23 and junior kayakers, indicating a linear increase from the junior category to professional levels. Higher relative power could be partly attributed to greater strength and muscle mass observed in professionals compared to U23 and juniors (Michael et al., 2009). Despite a similar body mass observed between age groups, professional sprint kayakers had a greater muscle mass compared to U23 and junior athletes. The positive association between higher muscle mass and better force and power outputs of kayak stroke has already been well elucidated (Hamano et al., 2015; Kukic et al., 2022). Hence, body composition could be considered a main differentiating parameter between sprint kayakers of different age groups.

In accordance with our hypothesis, international-level sprint kayakers exhibited better VO_2max, ventilatory threshold, muscular strength and power, body composition, and paddling performance. Provided such a vast difference, it could be recommended that to improve paddling performance, club-level athletes should focus on enhancing cardiorespiratory fitness, bio-motor abilities, and body composition to optimize their paddling performance.

Some limitations of the present study should be noted. Due to the limited presence of dedicated athletes competing across various distances, the arrangement of paddlers was not structured according to their specific racing distances. Moreover, the study’s cross-sectional nature prevents making conclusions about performance prediction, even though distinctions among groups were noted. As a result, longitudinal research is necessary to ascertain the precise utility of these variables in accurately predicting performance among young kayakers.

In conclusion, speed and endurance indicators of sprint kayaking (VO_2max, VT₁ and VT₂, PPO, APO, strength, and muscle mass) appear to be the primary distinguishing factor between junior sprint kayakers and the higher age categories. Significant differences in cardiorespiratory fitness indicators were also observed between U23 and professional kayak sprinters, with the latter indicating better 500 and 1,000-m TT performance, muscular strength and power, VT₁, but without differences in VO_2max, and VT₂. International-level athletes also showed superior cardiorespiratory fitness, bio-motor abilities, and body composition indicators than club-level sprint kayakers. While further longitudinal studies are required to validate these results, the current findings could aid coaches in prescribing training programs focusing on improving determining factors in paddling performance, as well as in predicting performance and identifying talent.