Work

Single-session estimation of cardiorespiratory fitness, lower-limb strength, and core strength using a wearable hip-joint exoskeleton

Year: 2026

Type: article

Abstract: Laboratory criterion tests for cardiorespiratory fitness and muscular strength are valid but require specialised equipment and trained personnel, limiting scalability in real-world settings. Wearable hip exoskeletons already deployed for exercise and rehabilitation can standardise short bouts while capturing kinetic and physiological signals, enabling compact “smart tests” for multi-domain fitness estimation without additional laboratory infrastructure. In healthy adults ( $n = 42$ ), a single-session knee-up protocol with a hip-joint exoskeleton yielded heart-rate–derived and kinetic features to estimate (i) cardiorespiratory endurance (estimated VO $_{2}$ max), (ii) lower-limb strength, and (iii) core strength. We prioritised simple multivariable linear regression and used polynomial+LASSO only as a comparator. Targets were validated by (i) benchmarking treadmill-estimated VO 2 max against directly measured VO 2 max in a feasibility subset ( $n = 30$ ) and (ii) correlating isometric abdominal crunch with plank hold time. Agreement was examined via Bland–Altman analysis. We also introduced absolute percentile-weighted and relative Pareto-based composite scores. Linear models explained 62–88% of the variance across the three fitness targets within the development sample (VO 2 max $R^2$ up to ${\sim }0.88$ ), with in-sample Bland–Altman analyses showing negligible mean biases (VO 2 max: 0.00 ml $\cdot$ kg -1 $\cdot$ min -1 ; lower-limb: 0.00 Load/BW; core: 0.00 Load/BW). Polynomial+LASSO did not provide consistent improvements over linear regression. Target-level checks supported convergent validity (treadmill-estimated VO 2 max vs. directly measured VO 2 max: $r = 0.92$ –0.94) and core capacity (crunch vs. plank: $r \approx 0.80$ , $\rho \approx 0.78$ ). Pairwise correlations among the three targets were strong ( $r = 0.78$ –0.82). Bootstrap resampling ( $B = 1000$ ) and Gaussian noise perturbation provided supplementary evidence regarding model stability within the development sample. The absolute composite summarised standing within sex–age peers, while the Pareto-based ranking highlighted balanced profiles. These proof-of-concept findings show that a brief, exoskeleton-guided single-session protocol can provide promising, internally consistent estimates of multi-domain fitness using simple linear regression, supporting interpretable, low-overhead deployment as a structured monitoring tool within existing exoskeleton-assisted sessions pending independent external validation.

Source: Scientific Reports

DOI: 10.1038/s41598-026-69403-8

Authors: Byungmun Kang, Hwang-Jae Lee, Dokwan Lee, YoonMyung Kim, DaeEun Kim

Institutions: Yonsei University, Samsung (South Korea), Samsung Electronics (South Korea)

Language: English

Topic: Cardiovascular and exercise physiology

Subfield: Complementary and alternative medicine

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $2,690