Common estimates of external training intensity for resistance exercise do not incorporate inter-set recovery duration, and might not reflect the overall demands of training. This study aimed to assess novel metrics of exercise density (ED) during resistance exercise, and how these related to a physiological marker of internal training intensity as well as traditional measures of external training intensity and volume. Thirteen males and seven females performed two bouts of resistance exercise focused on developing strength (5 sets of 5 repetitions with 5-repetition maximum; 180 s recovery) and hypertrophy (3 sets of 10 repetitions with 10-repetition maximum; 60 s recovery). Blood lactate concentration was measured to quantify internal training intensity. Specific metrics of external volume (mechanical work, volume load and total repetitions) and intensity (average weight lifted and ED) were calculated. Despite lower average weights and no difference in mechanical work or volume load, blood lactate was greater following hypertrophy compared with the strength condition. This finding was consistent with higher measures of ED in the hypertrophy compared with the strength condition. Greater ED during hypertrophy resistance exercise, along with the significant association with changes in blood lactate, indicates that ED metrics are reflective of the sessional intensity for resistance exercise.