Three teenagers have been arrested on suspicion of assault after a series of attacks on canal towpaths in Wolverhampton.
In nine separate attacks, dating back to 12 September, victims suffered injuries including cuts, broken ribs and a shattered kneecap.
The victims, aged 33 to 72, were assaulted as they walked near Wolverhampton Racecourse.
Police said three boys aged 13, 14 and 15 had been bailed pending inquiries.
The arrests followed work with local schools, West Midlands Police said.
They added that strict bail conditions prevented the teenagers from going near the canal network.
PC Joe Trusselle said the attacks had been carried out "for seemingly no other reason than getting a sickening personal kick".
In one of the attacks, a 51-year-old cyclist was pushed off his bike into the water and required surgery for a shattered kneecap.
PC Trusselle said he hoped the arrests would reassure the local community that the areas canals were safe places to walk.
West Midlands Police said patrols had been increased in the area.