Scientific Reports: Comparison of Plug-in Gait and CGM2.3 models reveals systematic differences in joint kinematics and kineticsThe study led by Tom Thiel compared the traditional Plug-in Gait (PiG) model with its updated version, CGM2. The models exhibit key differences in how segments are defined — direct kinematics in PiG vs. inverse kinematics in CGM2. This largely influenced calculated joint angles and moments: 31% and 104% greater knee extensor moments were observed during walking and one-leg squat, respectively, when using CGM2 vs. PiG. This difference can be largely explained by differences in the knee joint center location. Journal of Biomechanics: Influence of low-pass filtering strategies on lower limb joint moments during walkingThe study led by Valtteri Huttunen examined how low-pass filtering of kinematics and ground reaction forces affects joint moments calculated by the PiG model during walking. Clinical gait labs and many studies frequently use the PiG model with mismatched cutoff frequencies (e.g., 6 Hz for kinematics and 50 Hz for force plate data). Mismatched filtering caused non-physiological impact artifacts — especially sharp, artificial peaks in early-stance hip moments. In addition, the 15–15 Hz matched filter combination resulted in a 2× greater hip extensor moment compared with 6–6 Hz. Because joint moments are used to interpret muscle force production, such a difference may lead to misinterpretation of the true muscle mechanical output. 𝗞𝗲𝘆 𝗧𝗮𝗸𝗲𝗮𝘄𝗮𝘆:- Model and filtering choices matter even during low-impact activities such as walking. - Small methodological choices can have a large impact on biomechanical interpretation.

This time, ISEK was held in Jyväskylä, Finland. We organized a symposium entitled "Exoskeletons in gait assistance: opportunities, challenges & future directions" together with the Bionic and Rehabilitation Engineering group from Aalto University.In addition, Sara Ylijärvi gave a presentation entitled "Paraspinal muscle activation asymmetry during walking and running in adolescents with idiopathic scoliosis," and Valtteri Huttunen presented a poster entitled "Influence of low-pass filtering strategies on lower limb joint moments during walking."

Helsinki Gait and Motion Group was represented at the Nordic Movement Analysis Congress in Stockholm. Mika Peltoniemi gave a presentation titled "Acute effects of an ankle exoskeleton on the biomechanics and oxygen consumption of walking in typically developing children and children with cerebral palsy."In addition, Tom Thiel from our collaboration project with Metropolia University of Applied Sciences presented "Comparison of CGM2.3 and Theia3D kinematics and kinetics."

Max Thurston’s second PhD article examined the acute effects of a robotic exosuit on walking in children with cerebral palsy (CP). The study demonstrates that the exosuit can immediately improve ankle movement, increasing dorsiflexion during the swing phase and effectively alleviating drop-foot on the more-affected side. It also enabled more natural plantarflexion during push-off, compared to orthoses that typically restrict this motion. Although peak ankle moment was enhanced, this did not lead to increased positive power from the more-affected ankle. No significant changes were observed in muscle activity or energy cost, suggesting that the exosuit does not acutely influence these parameters upon initial use. These findings highlight the exosuit’s potential to support more typical gait patterns in children with CP. Read the full article here.

Isokinetic dynamometry (IKD) and inverse dynamics (ID) — two widely used methods to estimate joint moments — were found not to agree when applied to measure force outputs from ankle plantarflexors and knee extensors. Understanding these differences helps resolve contradictions in the literature and enable more accurate assessments of muscle and tendon function. Read the full article here.

Our presentations: Comparison of maximal joint moments measured by isokinetic dynamometer versus inverse dynamics method The choice of lowpass filter cutoff frequency affects the interpretation of joint moments in gait Comparing three coordinate systems in conventional gait model 2.3: knee moment insights from walking, single-leg squats and drop jumps Performance-injury conflict in lower extremity biomechanics during jumping and cutting movements

This time, we had only one presentation on the differences in joint moments measured by an isokinetic dynamometer versus the inverse dynamics method. See you next year at the Karolinska Institute!

Di Wang’s meta-analysis study examined whether different injury prevention interventions can change knee motion in a way that could reduce the risk of ACL injury (i.e., more knee flexion and less valgus motion during movement tasks). The results show that changes in knee motion were achieved only through external focus instructions and internal focus of attention in jumping tests, while no interventions could change knee motion in cutting movements. This movement specificity in the effectiveness of altering knee motion provides insight into efforts to reduce ACL injury risk. Find the article from here.

Maxwell Thurston’s first PhD article found a more uniform spatial-EMG amplitude distribution across the Gastrocnemius medialis muscle in adolescents with cerebral palsy (CP), compared to the distal emphasis observed in typically developing (TD) adolescents (see video below). Furthermore, this more uniform spatial-EMG distribution was associated with stronger ankle co-contraction and increased spasticity in the cerebral palsy group. Read the full article from here.

YLE science podcast about brain, body and assistive exoskeletons. Listen from here.

Our presentations: Insights from high-density EMG analysis during exoskeleton-augmented walking in patients with Cerebral Palsy A 30 minutes of walking reduces ankle joint stiffness in children with CP Are clinical measurements related to spasticity appearance in dynamic movement in CP?

Our presentation in ISEK: Towards understanding muscle activation asymmetry in idiopathic scoliosis – A pilot study

Our group has the following presentations in the ESMAC conference: Metabolic Cost Reductions Are Associated with Reduced Muscle Activity When Walking with a Robotic Exosuit in Patients with Cerebral Palsy Relationship between spastic catch measurements and ankle joint movement in walking and hopping in children with cerebral palsy Antigravity muscle efforts during walking determined in an inverse dynamics approach Patients with scoliosis have dysfunctional spinal muscles - a preliminary study

Helsingin Sanomat wanted to examine the effects of shoe cushioning on the biomechanics of running. Our analysis revealed that that leg stiffness is adjusted to accommodate different shoe cushioning properties. Read more.

Helsinki GMG is founded and growing. The purpose of this webpage is to inform about the research work of our group.