The aim of this study was to compare the exercise demands between two intermittent small-sided games (SSGs) and their temporal changes throughout SSGs repetitions, while controlling for total exercise duration. Exercise demands were recorded using wearable 10-Hz global positioning system technology with a 100-Hz accelerometer embedded and heart rate (HR) monitors in eight U17 male professional football players (age = 16.3 ± 0.5 years old) during two 18-min 4v4 plus goalkeepers SSGs based on long bouts (LB; 3 × 6 min) and short bouts (SB; 6 × 3 min) separated for 2-min rest. Total duration was 18 min, pitch dimensions were (length × width) 24 × 17 m and relative space per players was 51 m 2 . During LB, higher total distance, accelerations > 2 m s −2 , decelerations < − 2 m s −2 (Dec2), peak HR (HR peak ) and mean HR (HR mean ) were observed (ES = 0.5-7.4). During LB, explosive distance (> 1.2 m s −2 ) and Dec2 decreased from the 1st toward 3rd bout (ES = 0.6-1.5). During SB, HR peak and HR mean increased in the 2nd and 3rd (ES = 1.7-3.2) and then decreased in the 4th, 5th and 6th bout (ES = 0.7-3.5). The LB-based SSGs seem to produce greater physical and physiological demands than SB. However, SB induced greater fluctuations in HR while ensuring work rate maintenance across bouts.