"Although vertebral problems are regularly reported on riding horses, these problems are not always identified nor noticed enough to prevent these horses being used for work," the authors noted.
Nineteen horses from two riding centres were submitted to chiropractic examinations performed by an experienced chiropractor.
Beforehand, both horses' and riders' postures were observed during a riding lesson.
"The results show that 74 per cent of horses were severely affected by vertebral problems, while only 26 per cent were mildly or not affected," the authors found.
The researchers, Clémence Lesimple, Carole Fureix, Hervé Menguy and Martine Hausberger, found a correlation between the horses' neck height and curvature and the riders' position in the saddle.
"These findings are to our knowledge the first to underline the impact of riding on horses' back problems and the importance of teaching proper balance to beginner riders in order to increase animals' welfare."
They also noted: "Clear differences appeared between schools concerning both riders' and horses' postures, and the analysis of the teachers' speech content and duration highlighted differences in the attention devoted to the riders' position.
"It is interesting to note," they continued, "that riding teachers can greatly differ in the attention they devote to their riders' postures."
The authors, whose findings were published in the open access journal, PLoS ONE, pointed to earlier research indicating that improper riding techniques have been identified as a potential source of back problems.
Improper techniques needed to be addressed or treatment may well be in vain, they noted.
"Apart from cases with overt associated lameness, horses mainly express these problems through progressive or sudden changes in temperament, leading to increased aggressiveness towards humans or signs of escape attempts."
The authors said they focused their study on riding-centre horses ridden by unskilled riders. They hypothesised that undesirable hand or leg actions by the riders may impact on the horse.
Their findings revealed a correlation between poor posture by the horse during work and vertebral problems evaluated at rest.
They concluded: "Improper riding postures may have a strong effect on horses' postures at work that may also lead to chronic vertebral problems."
The authors pointed to a recent study that found that show horses, and especially dressage horses, exhibited higher emotional levels than unbroken or leisure horses.
"More recently, it was shown that the type and prevalence of abnormal behaviours performed in the box differed according to the type of work: dressage horses, in particular, exhibited more headshaking.
"Horses with mouth pain tend to avoid it by raising the head, which causes extension of the back.
"High neck posture associated with a raised head has been shown to be the most uncomfortable posture for horses, affecting motion.
"If riding techniques affect neck and head position, they may therefore repeatedly affect the thoracolumbar system and lead to potential chronic back problems."
They noted that their finding that 74 per cent of the horses in the study were severely affected by back problems was in agreement with another study which found 78 per cent of 443 horses investigated had potential back pain (vertebral lesions and/or soft tissue injury).