The Biering-Sorensen test used to assess the endurance of the trunk extensors and demonstrates good validity and his reliability in the evaluation of trunk muscles endurance with an intra rater reliability of 93.2%. 17, 18 Subject is made to lie down prone on the examination table with their upper border of iliac crest in alignment with border of table. The lower part of the body is held constant into the examination table through 3 straps folded across the ankle, knees and pelvis respectively and arms folded across the chest. The subjects maintain horizontal position of the upper body while the time is recorded. Once the subject reaches 240sec, the test is stopped.

The Y-balance test used to evaluate the asymmetrical balance and dynamic limits of stability in three different directions. The YBT is a reliable measure of dynamic balance with intraclass correlation coefficients ranging from 0.85 to 0.91 for intra-rater reliability and from 0.85 to 1.00 for inter-rater reliability.14 For the test, Y-shaped marking was made on the floor using a micropore tape. The posterior direction of the Y shaped marking was positioned each at 135 degrees from the previous and 90 degrees between them. 24 The participants were then instructed to stand on their right limb with the edge of their toes at the marked starting line. With their hands placed on their hips, they had to reach as far as possible with the non-stance limb in the anterior, posteromedial, and posterolateral directions. Three successful repetitions were performed in each direction, and the mean scores for each direction were used for the statistical analysis. To express reach distance as a percentage of limb length, the normalized value was calculated as reach distance divided by limb length then multiplied by 100%. Composite reach distance was the sum of the 3 reach directions divided by 3 times limb length, and then multiplied by 100%.

The BBS scale is highly reliable for measuring balance with an intra-rater reliability of 0.98. 15 The Berg Balance Scale is able to detect many clinically significant changes in balance with 95% confidence. 15 BBS is a combination of 14-item scale with a total score of 56.

Co-relational statistical analysis was done for this study using SPSS version 29 0

Table 2

Sorenson (Seconds)	Mean	S.D
Sorenson test	83.26	17.72

Table 3

Y balance test (cm)	Mean	S.D
Anterior
Right	78.70	11.39
Left	80.04	9.69
Posterolateral
Right	72.54	8.22
Left	71.28	7.39
Posteromedial
Right	78.70	12.61
Left	80.92	11.11
Y balance test total
Right	229.95	21.93
Left	232.24	21.66
Y balance score
Right	88.24	11.73
Left	89.16	12.09

M- Mean, S.D- Standard deviation

Table 5

Berg balance score	M	S.D
Berg balance score	30.13	3.59

M- Mean, S.D- Standard deviation

Table 6

Sorenson Vs. Berg balance score	Pearson’s correlations analysis
	r	p
Correlation analysis	0.035	0.727

r- Correlation coefficient, p- probability

The purpose of the study was to find out a relation between trunk extensor muscle endurance and dynamic stability among nurses. For this study 103 nurses were included of which 42 were male and 62 were female nurses. The mean age of the participants was 29.21 ±3.14 years. The trunk extensor muscle endurance and Dynamic Postural Stability were assessed using Beiring Sorenson’s Test, Y balance test and Berg’s balance scale respectively. The results shows that no significant relation was found between trunk extensor muscle endurance and dynamic postural stability.

A collective contribution of systems is necessary to have a good postural control and for maintaining balance. This is a complex process in which there is involvement of the CNS which comprises the brain and the spinal cord, on the other side peripheral nervous system which comprises of afferent and efferent pathways, sensory system which includes the sensory receptors, vestibular, visual system and lastly the musculoskeletal system. A collective contribution of these system in the controlling postural stability could be a reason for non-significant relation being found between trunk endurance and dynamic postural stability. 26

Our study results have been similar to the findings of Ozmen which suggested that core muscle endurance was not associated with dynamic balance. 27 Another study done by Krishna et al. also found no significant correlation been found to exist between core endurance and dynamic balance suggesting that core has an important and stabilizing part in the movement pattern of the lower extremity however endurance of the core muscle alone may not account much in dynamic balance. 28 Supporting our study findings, a study done by Behennah J et al observed no relation existing between trunk extensor endurance and dynamic balance in both subjects with and without Chronic low back pain. 29

Our study results show no significant relation have found between trunk extensor muscle endurance and dynamic postural stability. However, few of the previous studies contradict our findings. There has been evidence which shows that a decrease in muscular endurance could be a cause, as well as a consequence, of certain musculoskeletal related disorders. Low static tolerance in the extensor muscles of the back is associated with a higher incidence of low back pain (LBP), decreased consciousness of proprioception, poor balance and reduced productivity at work, increased muscle fatigue and overloaded soft tissues and passive structures of the lumbar spine.

The tensile strength or endurance of the torso has a greater effect on functional performance than flexor strength and maximum force. 27 Helbostad et al in their study of the consequences of fatigue of the muscles of the torso and lower extremities for balance and functional tasks confirmed that fatigue of the torso extensor muscles which may relate to poor endurance is associated with a violation of the somatosensory process, which leads to a reduction in stability and coordination. They concluded that static balance was affected by trunk extensor fatigue through an exaggerated postural sway. 30 A study by Anoop Joy et al concluded that a strong correlation existed between trunk extensor endurance and dynamic postural control and that a good amount off muscle endurance is necessary to maintain an erect posture and muscular imbalance can cause postural instability. 31

Our study suggests that trunk muscle endurance may not be a significant related factor impacting dynamic postural stability. Involvement of multiple systems in maintaining balance may be crucial toward attaining dynamic postural stability. Various kinetic and kinematic factors such as range of motion of hip joint strength of lower limb muscles may affect dynamic stability. 27 Control of balance which is a complex mechanism with different systems working together can also be an important factor effecting balance. Thus, focusing on improving the trunk muscle endurance may not be sufficient to enhance balance and reduce the risk of Low back ache in Nurses.

This study concludes that there was no significant relationship between the strength of the trunk muscles and dynamic postural stability among nurses. As a good dynamic stability is dependent on multiple systems working in a collective manner, trunk muscle endurance may not be having a significant contribution towards dynamic postural stability.