Biomechanical and physiological effects of a passive upper-body exoskeleton during stair ascent and descent.

Heart rate was reduced during both stair ascent and descent when wearing the CarrySuit® exoskeleton while carrying a 12-kg load.

• Fifteen female and fifteen male participants were tested in the study.
• Participants carried a 12-kg load with and without the passive upper-body exoskeleton.
• Heart rate reduction was observed during both ascent and descent conditions.
• The reduction applied to all participants regardless of sex.

Biceps brachii and erector spinae muscle activity were reduced during both stair ascent and descent when wearing the exoskeleton, with the exception of females during descent.

• Muscle activity reductions in biceps brachii and erector spinae were observed in both ascent and descent conditions.
• In females during descent, muscle activity in these muscles remained comparable between exoskeleton and no-exoskeleton conditions.
• The effect was assessed through electromyographic measurements of muscle activity.
• The finding applied to both male and female participants during ascent, but diverged by sex during descent.

An increase in upper-leg muscle activity was observed only in males during stair ascent when wearing the exoskeleton.

• This increase was sex-specific, occurring only in male participants.
• The effect was limited to the stair ascent condition.
• No corresponding increase in upper-leg muscle activity was observed in female participants.
• This suggests a compensatory loading pattern in the lower extremities in males during ascent.

Lower-leg muscle activity was reduced during stair descent for all participants when using the exoskeleton.

• This reduction was observed across all participants, regardless of sex.
• The effect was specific to the stair descent condition.
• Lower-leg muscle activity was measured as part of the overall muscle activity assessment.

Some side-based asymmetries in lower-limb muscle activation were observed but were generally modest when using the exoskeleton.

• Asymmetries were detected in lower-limb activation between left and right sides.
• The asymmetries were described as 'generally modest' when the exoskeleton was worn.
• This finding relates to the bilateral distribution of muscular effort during stair negotiation.

Use of the CarrySuit® was associated with reduced joint range of motion, with the effect being broader in males than females.

• In males, reductions in range of motion were observed in the shoulders, elbows, pelvis, hips, and thorax.
• In females, reductions in range of motion were limited to the neck and thorax.
• Joint range of motion was assessed across multiple body segments during stair negotiation.
• The more widespread reductions in males suggest greater postural constraint imposed by the exoskeleton in that group.

Increases in joint range of motion were observed in specific lower-extremity and upper-extremity joints when using the exoskeleton.

• In females, increases in range of motion were observed in the ankles, knees, hips, and shoulders.
• In males, increases in range of motion were observed in the ankles and knees.
• These increases suggest compensatory or facilitated movement in lower-limb joints concurrent with upper-body support.

All participants reported lower perceived discomfort when using the exoskeleton, with broader relief observed among male users.

• Perceived discomfort was assessed as a perceptual outcome alongside physiological and biomechanical measures.
• The reduction in perceived discomfort was observed across all 30 participants.
• Male participants experienced broader discomfort relief compared to female participants.
• This perceptual improvement was consistent with the physiological and biomechanical findings.