The results of this study support the recommendation
to use strength-endurance and the cranio-cervical flexion
(CCF) exercises for the cervical muscles as treatment interventions
for patients with chronic neck pain19, 20)
. The
results were also in agreement with previous studies that demonstrated that pain can be reduced by strength training19–22)
and endurance training21, 22)
. Moreover, general
exercises like strength and endurance training, as well as
specific exercises such as cranio-cervical flexion of deep
cervical flexor muscles have been shown to decrease neck
symptoms18)
.
In the present study, the neck pain and disability index
significantly improved after 12 weeks of exercise intervention
in all the exercise groups. This indicates that exercise
caused the changes in VAS and NDI score of females who
had chronic neck pain. This result was in agreement with
previous studies29, 30)
which showed the same trend of decrease
in NDI score and VAS after exercise interventions.
The improvement in pain and disability in the three exercise
groups were not only statistically, but also clinically
significant. The decrease in VAS was 16.32 mm in the
strength-endurance exercise group, 13 mm in the CCF exercise
group and 44.6 mm in the combined exercise group.
The decreases in NDI score were 13.51 in the strength-endurance
exercise group, 15.55 in the CCF exercise group
and 13.52 in the combined exercise group. The reductions in
pain and neck disability were significantly different among
the control and all three exercise groups. There was a tendency
of greater reduction in neck pain in the combined exercise
group compared to the strength-endurance exercise
and CCF exercise groups.
The muscle activities during the typing task showed differences
between before and after in all the exercise groups,
but there was no significant difference between before and
after the intervention in the control group in both the right
and left cervical erector spinae, sternocleidomastoid, and
anterior scalenes. This result indicates that the exercise interventions
caused changes in muscle recruitment during
the typing task. The upper trapezius muscle on both the
right and left sides showed a significant reduction in muscle
activity after the interventions in all the exercise groups.
There was a trend of increased in RMS in the control group,
which performed no exercise intervention, and there were
no significant differences among the RMS values of the
three exercise groups. The subjects in the control group had
RMS values that were greater than those of the other groups.
This indicates that the exercise interventions of groups 1, 2
and 3 had the effect of decreasing the RMS value, whereas,
the control group showed no change in RMS values during
the typing task.