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Active trunk exercises require more muscle activity in mature than in young adults

Valentin, Stephanie; Licka, Theresia


Theresia Licka


Introduction and Objectives: Reductions in muscle strength [1], changes in motor control patterns [2] and muscle morphology [3] are known to occur with ageing. However, the effect of age on trunk muscle activity during active trunk exercises has not been widely investigated, even though spinal range of motion is known to reduce with age [4]. The aim of this study was to compare the age differences in activity of the rectus abdominis (RA), obliquus internus (OI), obliquus externus (OE), and erector spinae (ES) muscles during flexion and extension exercises performed in upright (U) and 4- point kneeling (4P) postures.
Methods: Twenty-four healthy participants (12 young, aged 18-25 years; 12 mature, aged 45-60 years) were included. Reflective markers were attached over the spinous process of the 11th thoracic vertebra (T11), the head, the left and right styloid processes, and lateral femoral condyles. Three-dimensional kinematic data were collected using 10 high speed cameras (Eagle Digital Real Time System, Motion Analysis Corp., 120Hz). Surface EMG electrodes (Delsys Trigno, 1200Hz) were attached over the left and right ES, RA, OE, and OI after skin preparation. Data were collected during three repetitions of 10s of flexion and extension movements in U and 4P. Participants were instructed to perform each movement to their end range and return to the starting posture in one fluent movement. Raw EMG data were resampled, rectified, zero-mean offset, and a 4th order low pass Butterworth filter applied. Processed EMG data from 0.5s before movement onset and 0.5s after movement cessation (both based on vertical T11 movement) were included for analysis. EMG data were normalised to the maximally observed muscle activity from any trial and movement for each muscle, and the maximum and 1st, 2nd, and 3rd quartiles (Q1, Q2, Q3) calculated for the concentric phase (conc) and eccentric phase (ecc) of muscle activity. Due to non-normally distributed data, each EMG parameter was compared between the young and mature groups using a Mann-Whitney U test.
Results: There were no significant differences in T11 vertical displacement between the age groups. In the young group, median values across all muscles, postures and movements ranged from 6.91 - 33.29% for Q1, 7.17 - 42.05% for Q2, 7.53 - 66.02% for Q3, and 10.96 - 86.78% for the maximum. In the mature group, these values were 9.39 - 36.67%, 11.19 - 53.87%, 12.24 - 74.98%, and 15.33 - 89.08% respectively. In 4P, there were no significant differences between the young and mature group for any movement, muscle, or parameter, except for RA right (flexion Q2 ecc; extension Q1, Q2, Q3 ecc; p<0.05).
Conclusion: Differences in trunk muscle activation were observed between healthy young and mature participants, although this was dependent on movement direction and posture adopted. Interestingly, in each significant finding, the mature group scored higher normalised EMG values compared to the young group, indicating that mature adults require greater muscle activity based on a peak dynamic normalisation method in comparison to young adults to attain similar trunk displacement. In U, differences between the age groups were found in all muscles and across all phases (concentric, maximum, eccentric). However in 4P, which is a posture considered to be relatively novel, fewer significant differences occurred between the age groups, with only RA right in the eccentric phase showing significant differences. This unilateral finding may be related to the establishment of more marked laterality with age in commonly adopted postures.

Presentation Conference Type Conference Paper (unpublished)
Conference Name XXV Congress of the International Society of Biomechanics (ISB 2015 Glasgow)
Start Date Jul 12, 2015
End Date Jul 16, 2015
Deposit Date Feb 8, 2023
Publisher URL