Sit-to-walk strategy classification in healthy adults using hip and knee joint angles at gait initiation

Abstract

Forward continuation, balance, and sit-to-stand-and-walk (STSW) are three common movement strategies during sit-to-walk (STW) executions. Literature identifies these strategies through biomechanical parameters using gold standard laboratory equipment, which is expensive, bulky, and requires significant post-processing. STW strategy becomes apparent at gait-initiation (GI) and the hip/knee are primary contributors in STW, therefore, this study proposes to use the hip/knee joint angles at GI as an alternate method of strategy classification. To achieve this, K-means clustering was implemented using three clusters corresponding to the three STW strategies; and two feature sets corresponding to the hip/knee angles (derived from motion capture data); from an open access online database (age: 21–80 years; n = 10). The results identified forward continuation with the lowest hip/knee extension, followed by balance and then STSW, at GI. Using this classification, strategy biomechanics were investigated by deriving the established biomechanical quantities from literature. The biomechanical parameters that significantly varied between strategies (P < 0.05) were time, horizontal centre of mass (COM) momentum, braking impulse, centre of pressure (COP) range and velocities, COP–COM separation, hip/knee torque and movement fluency. This alternate method of strategy classification forms a generalized framework for describing STW executions and is consistent with literature, thus validating the joint angle classification method.

Hindlimb kinematics, kinetics, and muscle dynamics during sit-to-stand and sit-to-walk transitions in emus (Dromaius novaehollandiae)

“…Emus demonstrated a sequential joint excursion from proximal to distal during the transition like humans do (Pandy, Garner and Anderson, 1995), an observation also seen in greyhounds (Ellis, Rankin and Hutchinson, 2018). Both emu movements involved generating substantial forward momentum, positioning the COM behind the toes at heel-off, resembling the ‘momentum transfer’ or ‘forward momentum’ strategy observed in humans (Hughes, 1996; Norman-Gerum and McPhee, 2020; Perera et al ., 2023). However, it is important to note the differences between emus and humans in performing the two tasks: while human STW demands greater stability, often with a longer flexion (or pitch) momentum period sacrificing speed or efficiency (Kerr, Durward and Kerr, 2004), emus had a relatively small body pitch movement and displayed a faster flexion momentum period in STW than in STS ( Table 1 ).…”

“…However, it is important to note the differences between emus and humans in performing the two tasks: while human STW demands greater stability, often with a longer flexion (or pitch) momentum period sacrificing speed or efficiency (Kerr, Durward and Kerr, 2004), emus had a relatively small body pitch movement and displayed a faster flexion momentum period in STW than in STS ( Table 1 ). Emus also seem to have a relatively smaller braking impulse compared to humans during the transition (e.g., Magnan, McFadyen and St-Vincent, 1996; Perera et al, 2023), especially when performing the STW task (Table 1). The braking impulse reduces forward momentum and presumably allows a focus on stability and postural control when standing up (Perera et al, 2023).…”

“…Emus also seem to have a relatively smaller braking impulse compared to humans during the transition (e.g., Magnan, McFadyen and St-Vincent, 1996; Perera et al, 2023), especially when performing the STW task (Table 1). The braking impulse reduces forward momentum and presumably allows a focus on stability and postural control when standing up (Perera et al, 2023). These differences suggest that emus transition from sitting to walking while maintaining stability, possibly due to their cranially positioned COM and use of passive support mechanisms.…”

“…In all trials, the birds started in a near-symmetrical, crouched position. We classified trials where minimal forward movement occurred upon standing upright as a STS transition according to Riley et al ., (1991), and defined trials that involved at least one complete stride forward during rising as a STW transition per Perera et al ., (2023). We defined the STS transition using three primary phases marked by events based on human STS phase definitions (Kralj et al ., 1990; Schenkman et al ., 1990) ( Figure 1C ): (i) flexion momentum phase: this phase began at movement onset (identified by a 5 % change in the vertical ground reaction force (GRF)) and concluded when the tarsometatarsus lifted off from the ground (marked by a 5 mm change in the ankle marker height); (ii) ascending phase: started at heel-off and continued until minimum variation was observed in the vertical and cranial-caudal GRF (determined via the root mean squared method); (iii) stabilisation phase: started at the end of the ascending phase and ended when the vertical GRF equalled body weight and fluctuations of 0.1 % – characteristic of quiet standing – were detected.…”

“…In humans, both STS and STW require considerable muscle strength and coordination for task execution and balance control (Ellis et al ., 1984; Schultz et al ., 1992; Doorenbosch et al ., 1994; Roebroeck et al ., 1994; Riley et al ., 1997; Dehail et al ., 2007; Yoshioka et al ., 2009), or older adults, these activities even approach the upper limits of muscle capacity (Hughes, 1996; Hortobágyi et al ., 2003). However, despite extensive studies on movement patterns and muscle engagement (Hughes et al ., 1994; Smith et al ., 2020; Perera et al ., 2023), the control strategies used during these movements remain elusive even for humans (e.g., Pandy, Garner and Anderson, 1995; Bobbert et al ., 2016; Actis et al ., 2018; Shia et al ., 2018). Remarkably, research on biomechanics of STS and STW in animals is extremely scarce, with only three studies on dogs as examples (Feeney et al ., 2007; Ellis et al ., 2018; Triviño et al ., 2023),.…”