Performing physical activity is considered health promoting but may induce a need for subsequent rest periods. This study aimed to determine the within-day interactions between vigorous physical activity (VPA) and sedentary behaviour (SB) in participants with low cardiorespiratory fitness. We tested the hypothesis that VPA is associated with a temporary subsequent increase in SB. One week of accelerometer data containing a minimum of one 10-min bout of VPA from 62 participants with low cardiorespiratory fitness (31-50 years old) were obtained from the MILE study. A comparison of SB was made between days with a bout of VPA and days without (control). Due to a positive association between VPA and number and duration of sedentary bouts, the time accumulated in both uninterrupted and total sedentary bouts were 27 (95% CI, 10-45) min and 29 (95% CI, 9-50) min higher on VPA days compared to control days (P < 0.05). Our results indicate that in participants with low cardiovascular fitness, unprompted VPA is positively associated with an increase in subsequent sedentary time. We propose that such VPA-associated sedentary time may be viewed as part of a healthy activity pattern.