Technological advancements in the analysis of human motion and posture management through digital devices

Table 1 Studies investigating the reliability of inertial measurement unit sensors

Ref.	Sensor/position	Comparison system	Results	Outcomes
Qiu et al[29], 2016	3 magnetic angular rate and gravity/thigh, shank, and foot	Vicon	Position accuracy of 0.3%, the ΔXY radial distance error of 0.82% and the distance error of 0.27%, position error of 0.4%	The combination of distributed wearable sensors with the Denavit–Hartenberg convention resulted in a promising tool for tracking lower limb movements
Sprager et al[30], 2015	1 multi-sensor platform integrated into a smart garment/knee	NP	Good activity discrimination can be achieved based RMSE and SD from flexible sensor, acceleration and gyroscope data	Preliminary results show that walking, running, stairs climbing can be discriminated based on the data collected
Cresswell et al[33], 2017	4 Shimmer3 sensor nodes/all sides of the shank	NP	The results of the fixed effects models highlighted the discrepancies between front–back mounting versus inner–outer mounting	For y-axis gyroscope data, the variation is mostly influenced by mounting location. Mounting location should not vary but if it has to vary, it is better for it to vary between inner and outer leg mounting locations
Fusca et al[35], 2018	1 IMU/posterior CoM	Elite (BTS)	Mean absolute percentage error of: Stride time is 5.7%; Cadence is 4.9%; Step's length is 5.6%; Step's speed is 13.5%	The use of IMU at CoM presents a good reliability for carrying out ambulatory, long-term, and ecologic kinematic of gait analysis
Saggio et al[36], 2020	7 IMU/pelvis, thighs, shanks and feet	Vicon	Joints ROMs RMSE and ICC PCC > 0.75, Reliability all the ICC > 0.975	IMUs sensors showed a high reliability on joints' movement and walking test

IMU: Inertial measurement unit; ICC: Intra-class correlation coefficients; RMSE: Root mean square error.

Table 2 Main features of motion analysis systems

Motion analysis systems	Capture system	Anatomical landmark	Recording system
Optoeletronic measurement system	Stereoscopic 3D	Passive or active markers placed	Multi-IR cameras with stroboscopic LED
Microsoft Kinect	ToF method	Markeless	1 RGB - IR Camera
IMU	9 DOF	Sensor placed with elastic band	Microprocessor processing raw data

LED: Light-emitting diode; DOF: Degree of freedom; ToF: Time of flight; IMU: Inertial measurement unit; RGB: Red, green, blue.

Table 3 Studies investigating the reliability of rasterstereography to evaluate the spine

Ref.	Aim	Coort	Results	Conclusion
Mohokum et al[84], 2010	To determine reproducibility of rasterstereography for kyphotic and lordotic angles, trunk length, and trunk inclination	51 healthy volunteers	Cronbach-α for the intratester-reliability of the kyphotic angle ICT-ITL (max.) between 0.921 and 0.992. The intertester-reliability for the same parameter is 0.979 (95%CI)	The reliability revealed good results, both for intratester and for intertester reliability of rasterstereography in kyphotic and lordotic parameters trunk length and trunk inclination
Guidetti et al[85], 2013	To determine intra- and interday reliability of spine rasterstereographic system Formetric 4D with and without reflective markers.	26 healthy volunteers with markers (M), 26 healthy volunteers without markers (NM)	In M group, for intra- and interday reliability coefficients were 0.971, 0.963, and 0.958 (ICC) and 0.987, 0.983, and 0.985 (Cα) for trunk length, kyphotic angle, and lordotic apex, respectively. In NM group, they were 0.978, 0.982, and 0.972 and 0.989, 0.991, and 0.991 for trunk length	The presence of the markers is not necessary for the intraday evaluations and can play a disturbing role for the interday evaluations, because of the repositioning process
Michalik et al[86], 2020	To study the spinal and pelvic position under dynamic conditions and compare it to static measurements using a rasterstereographic system.	121 healthy volunteers (56 females; 65 males)	Trunk inclination (5.31° vs 6.74°), vertebral kyphotic angle (42.53° vs 39.59°), and surface rotation (3.35° vs 3.81°) increase under dynamic conditions (P < 0.001). Trunk shows significant changes during walking compared to static conditions (P < 0.001)	The spinal posture differs between females and males during standing and during walking. Rasterstereography is a valuable tool for the dynamic evaluation of spinal posture and pelvic position
Albertsen et al[91], 2018	To investigate whether the clinical Matthiass test can be objectified by means ofdynamic rasterstereography in children.	101 healthy children	Cluster analysis identified two groups with different postural performance levels during the modified Matthiass Test. Low performers showed a higher increase in backward lean, kyphosis and lordosis (4°–5°, respectively) compared to high performers	Modified Matthiass Test applied with Rasterstereography can discriminate between low and high posture profile among children

Table 4 Application outline of each mentioned system

		Vicon	Microsoft Kinect	IMU	Electromagnetic	Rasterstereography	Kinovea	PostureScreen	Coach’s Eye
Field of application	Clinical	High	Medium	Low	Medium	High	Low	NA	NA
	Sport	High	High	Medium	Low	NA	High	NA	Medium
	Posture	High	High	Low	Medium	High	High	Medium	Low
	Surgery	High	NA	NA	NA	Medium	NA	NA	NA
System potential	Accuracy	High	High	Medium	High	Medium	Medium	Medium/Low	Medium/Low
	Reliability	High	High/Medium	Medium	High	High	Medium	Medium/Low	Medium/Low
	Validity	High	High/Medium	Medium	Medium	High	Medium	Low	Low
	Reproducibility	Low	High	Low	Medium	High	Medium	Low	Low
Other characteristics	Outdoor	NA	Available	Available	NA	NA	Available	Available	Available
	Markers/Sensors	Required	NR	Required	Required	NR	NR	NR	NR
	Time required	High	Low	Medium	Medium	Low	Low	Low	Low
	Cost	High	Medium	Low	High	Medium	Low	Low	Low

NA: Not available; NR: Not required.