Measurement of pain sensations
The test subjects were between 15 and 55 years old, mostly men, and included both experienced gym-goers and people who had only been exercising for a few weeks. The workouts reflected the range of equipment available in gyms, like weight training equipment with free weights and machines for different muscle groups, but also open space mobility training such as aerobics and cross fit.
Participants were asked daily for a week if they experienced muscle pain. If the answer was "yes", they were asked to define in which of eight different body zones they felt pain (neck, shoulder, elbow, wrist/hand, back, hip/thigh, knee, and/or ankle/foot).
“A limitation of the study is that we captured pain sensations that in many cases were caused by minor muscle injuries, but which did not necessarily involve an injury. Pain sensation was the key”, says Mamunur Rashid.
Participants from 74 gyms
In the group with a trainer with less than one year's experience, muscle pain was more than twice as common, compared to those whose trainer had more than five years' experience. If the trainer had between one- and five-years’ experience, the risk of pain was also higher, but only about 20% higher than for the group that hired the most experienced trainers.
Participants in the study engaged in either strength training, flexibility training or both at 74 different gyms in Bangladesh, and were coordinated by Sohel Ahmed, a physiotherapist working in a Bangladeshi hospital.
“Training in Bangladeshi gyms is very similar to that in Sweden. One difference is that there are usually small groups sharing a trainer during strength and other types of training, whereas in Sweden you are almost usually alone with the trainer when you do strength training or independent training”, says Manzur Kader, a doctor of physiotherapy.
The researchers also investigated whether the trainer's education had any impact on pain perception and minor injuries but did not get a clear answer.
“Education is clearly important, but we need a larger data set with sufficient spread in terms of coaches' educational qualifications and experience to determine what impact it may have. What we could see clearly was that experience matters a lot. I think one explanation for this is that coaches develop as instructors over time and can more clearly demonstrate how to train to avoid injuries when they are more experienced” says Mamunur Rashid.