The effect of age, prolonged seated work and sex on posture and perceived effort during a lifting task

Highlights

• Lumbar spine range of motion in flexion lower in older compared to younger adults.

• No change in lumbar angles during lifts in young adults following seated work.

• Reduced lumbar flexion during lifts among older adults following seated work.

• There was no effect of age on perceived effort during lifting tasks.

• Completion time of lifts was longer in older compared to younger adults.

Abstract

The purpose of this investigation was to determine the effect of prolonged seated work, lift task, age and sex on normalized lumbar angles, thoracic angles, perceived effort and duration of lifts. A total of 17 young and 17 mature participants were recruited with an average (standard deviation) age of 23.8 (5.0) years and 63.7 (3.9) years, respectively. Participants completed 3 different floor to knuckle lifts before and following 90 min of seated work. The lifts included; (i) 7 kg symmetrical, (ii) 4.5 kg symmetrical and (iii) 4.5 kg asymmetrical. Prolonged seated work and age interacted to affect normalized peak lumbar angles (p = 0.0469) where older adults adopted 56(15)% flexion after seated work compared to 67(16)% among younger adults. Older adults took significantly longer to complete the lifting tasks compared to younger adults while age did not affect perceived effort across lifting tasks. Older workers may require age specific interventions given age specific responses.

Introduction

The working population is aging (Carrière and Galarneau, 2011; Toossi, 2012) in many industrialized countries and has implications for workplace musculoskeletal injury prevention. Workers over 40 are represented in occupations with heavy physical demands including construction (Arndt et al., 1996; Petersen and Zwerling, 1998) and general labour/repair (Zwerling et al., 1996). Epidemiological evidence indicates low back pain increases in severity with increasing age (Dionne et al., 2006; Macfarlane et al., 2012) and the frequency of low back pain reporting peaks in middle age (Cassidy et al., 2005; Macfarlane et al., 2012; Parsons et al., 2007; Papageorgiou et al., 1995). Given that middle aged and older workers tend to sustain more severe musculoskeletal injuries at work compared to younger workers (Breslin et al., 2003; Smith et al., 2014; King et al., 2009; Peek-Asa et al., 2004; Smith and Berecki-Gisolf, 2014), an understanding of how musculoskeletal changes across the life course affect the performance of occupationally relevant materials handling tasks is of importance to determine if age dependent injury prevention strategies are necessary.

Occupational lifting has been investigated previously for links to injury risk and task performance differences across age. In fact, among workers aged between 51 and 61 years, self-reported exposure to heavy lifting was the factor most strongly associated with occupational injury (Zwerling et al., 1996). Comparisons of lifting technique between older and younger novice (Song and Qu, 2014a, 2014b; Boocock et al., 2015) and experienced (Chen et al., 2017) lifters have recently been completed in a laboratory environment. Novice older lifters have lower peak trunk flexion during lifting compared to younger novice lifters in symmetric (Song and Qu, 2014a; Boocock et al., 2015) and asymmetric lifting (Song and Qu, 2014b). After 20 min of continuous lifting, younger participants (20–31 years) increased peak lumbar flexion by an average of 18% over the course of a 20 min lifting protocol reaching almost maximal values of lumbar range of motion whereas older participants (43–54 years) increased peak lumbar flexion by an average of 4%, reaching 82% of maximum flexion range of motion (Boocock et al., 2015). Furthermore, older novice lifters (aged either 43–54 years or over 55 years) have been shown to have slower trunk angular velocity in extension compared to younger novice lifters (aged 20–31 years or 20–30 years) (Boocock et al., 2015; Song and Qu, 2014a, respectively).

The performance of lifting tasks may be impacted by prolonged sitting exposures and age-related functional changes in spine tissues with implications for injury. Previous work has demonstrated that prolonged sitting has an effect on passive properties of spine tissue and spine angles during a lifting task in young adults. Specifically, peak lumbar spine flexion angles were reduced during both lifting and lowering phases of a floor to waist height lift following 60 min of continuous sitting in young adults (Howarth et al., 2009). A potential mechanism of this change may be due to an increase in passive spine stiffness in response to prolonged sitting in young adults (Beach et al., 2005). High flexion tasks load the passive tissues of the spine including, inactive muscles, ligaments or the intervertebral discs given the flexion-relaxation of the low back musculature (Dolan et al., 1994). Alterations in passive tissue properties during high flexion tasks may alter injury risk, and this risk may be higher in older adults. In general, back extensor strength decreases with increasing age (Sinaki et al., 2001; Champagne et al., 2009; Yassierli et al., 2007; Singh et al., 2011, 2013) and low back range of motion decreases with increasing age (Dvorak et al., 1995; McGill et al., 1999; Taylor and Twomey, 1980; Sullivan et al., 1994). Increased age has been shown to increase baseline passive spine stiffness in flexion (Shojaei et al., 2016; Gruevski and Callaghan, 2019). Given these age-related functional changes, it is unclear how prolonged seated work and age will affect the performance of a variety of different lifting tasks. The primary purpose of this study was to determine the effect of prolonged seated work, age, sex and lift type on peak thoracic flexion angles and peak normalized lumbar flexion angles, duration of lift and ratings of perceived effort. A secondary purpose was to determine baseline differences in lumbar range of motion across age and sex.