Walking or balancing on a slackline has gained increasing popularity as a recreational and school sport, and has been found to be suitable for developing neuromuscular control. The metabolic requirements for neuromuscular control on slackline, however, have not been well described. Therefore, the aim of the study was to determine the metabolic demands of slacklining in less and more advanced slackliners. Nineteen slackliners performed several 4 min balance tasks: parallel and one-leg stance on stable platform (2LS and 1LS), 1 leg stance on a slackline (1LSS), walking at a self-selected speed and at a given speed of 15 m min −1 on a slackline (WSS and WGS). Expired gas samples were collected for all participants and activities using a portable metabolic system. During1 LS and 1LSS, there were 140% and 341% increases in oxygen uptake (V ̇O2 ) with respect to V ̇O2 rest, respectively. During slackline walking, V ̇O2 increased by 460% and 444% at self-selected and given speed, respectively. More advanced slackliners required mean metabolic demands 0.377 ± 0.065 and 0.289 ± 0.050 kJ•kg −1 •min −1 (5.7 ± 0.95 and 3.9 ± 0.6 MET) for WGS and 1LSS, respectively, whilst less advanced slackliners, 0.471 ± 0.081 and 0.367 ± 0.086 kJ•kg −1 •min −1 (6.4 ± 1.2 and 5.0 ± 1.1 MET) for WGS and 1LSS, respectively. Our data suggest that balancing tasks on slackline require V ̇O2 corresponding to exercise intensities from light to moderate intensity. More advanced slackliners had a ∼25% reduced energy expenditure when compared with lower ability counterparts during simple balance tasks on the slackline. Highlights. Balancing on a slackline is metabolically demanding and slackline training is suitable not only to develop neuromuscular control but also to meet cardiovascular fitness demands. . Improved postural control demonstrated by skilled slackliners reduces by ∼25% metabolic cost of balancing tasks on a slackline when compared to less skilled counterparts. . Falls during slacklining increase the metabolic demands of the activity. Three falls per minute during walking on a slackline increase the oxygen uptake by ∼50%.