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Background: Clinical gait analysis (CGA) is a systematic approach to comprehensively evaluate gait patterns, quantify impairments, plan targeted interventions, and evaluate the impact of interventions. However, international standards for CGA are currently lacking, resulting in various national initiatives. Standards are important to ensure safe and effective healthcare practices and to enable evidence-based clinical decision-making, facilitating interoperability, and reimbursement under national healthcare policies. Collaborative clinical and research work between European countries would benefit from common standards., Research Objective: This study aimed to review the current laboratory practices for CGA in Europe., Methods: A comprehensive survey was conducted by the European Society for Movement Analysis in Adults and Children (ESMAC), in close collaboration with the European national societies. The survey involved 97 gait laboratories across 16 countries. The survey assessed several aspects related to CGA, including equipment used, data collection, processing, and reporting methods., Results: There was a consensus between laboratories concerning the data collected during CGA. The Conventional Gait Model (CGM) was the most used biomechanical model for calculating kinematics and kinetics. Respondents also reported the use of video recording, 3D motion capture systems, force plates, and surface electromyography. While there was a consensus on the reporting of CGA data, variations were reported in training, documentation, data preprocessing and equipment maintenance practices., Significance: The findings of this study will serve as a foundation for the development of standardized guidelines for CGA in Europe., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Three-dimensional (3D) cameras used for gait assessment obviate the need for bodily markers or sensors, making them particularly interesting for clinical applications. Due to their limited field of view, their application has predominantly focused on evaluating gait patterns within short walking distances. However, assessment of gait consistency requires testing over a longer walking distance. The aim of this study is to validate the accuracy for gait assessment of a previously developed method that determines walking spatiotemporal parameters and kinematics measured with a 3D camera mounted on a mobile robot base (ROBOGait). Walking parameters measured with this system were compared with measurements with Xsens IMUs. The experiments were performed on a non-linear corridor of approximately 50 m, resembling the environment of a conventional rehabilitation facility. Eleven individuals exhibiting normal motor function were recruited to walk and to simulate gait patterns representative of common neurological conditions: Cerebral Palsy, Multiple Sclerosis, and Cerebellar Ataxia. Generalized estimating equations were used to determine statistical differences between the measurement systems and between walking conditions. When comparing walking parameters between paired measures of the systems, significant differences were found for eight out of 18 descriptors: range of motion (ROM) of trunk and pelvis tilt, maximum knee flexion in loading response, knee position at toe-off, stride length, step time, cadence; and stance duration. When analyzing how ROBOGait can distinguish simulated pathological gait from physiological gait, a mean accuracy of 70.4%, a sensitivity of 49.3%, and a specificity of 74.4% were found when compared with the Xsens system. The most important gait abnormalities related to the clinical conditions were successfully detected by ROBOGait. The descriptors that best distinguished simulated pathological walking from normal walking in both systems were step width and stride length. This study underscores the promising potential of 3D cameras and encourages exploring their use in clinical gait analysis.

Aim: To explore whether subgroups of adults with cerebral palsy (CP) with different fatigue diurnal profiles can be discerned, and to explore whether sleep, physical activity, or health-related fitness are associated with these profiles., Method: Thirty-two adults (median age 29 years 8 months; range 20-54 years; 11 males, 21 females) with spastic CP (Gross Motor Function Classification System levels I-III) with physical activity-related fatigue complaints participated. Real-time fatigue and physical activity were assessed for 7 consecutive days by short message service text four times during the day and by wearing an accelerometer respectively. Sleep was assessed by the Pittsburgh Sleep Quality Index, and fitness by assessing body composition and aerobic capacity. Latent class growth modelling was used to classify subgroups according to their diurnal profiles of real-time fatigue. Univariable multinomial logistic regression analysis explored whether participant characteristics, sleep, physical activity, or health-related fitness were associated with diurnal profiles., Results: Three distinct fatigue diurnal profiles were identified: stable low (n = 10), increasing (n = 14), and stable high (n = 8). Only aerobic capacity was associated with fatigue profiles (odds ratio 1.15, 95% confidence interval 1.00-1.34; p = 0.05)., Interpretation: Fatigue in adults with CP may be low or high stable or may increase during the day. These findings indicate the relevance of assessing fatigue variability., What This Paper Adds: We found three patterns of daily fatigue in adults with cerebral palsy (CP). Only aerobic capacity was associated with fatigue profiles in adults with CP. Moment-to-moment variations in fatigue can help with personalized fatigue management., (© 2022 The Authors. Developmental Medicine & Child Neurology published by John Wiley & Sons Ltd on behalf of Mac Keith Press.)

Purpose: To evaluate the effects of a combination of wheelchair mobility skills (WMS) training and exercise training on physical activity (PA), WMS, confidence in wheelchair mobility, and physical fitness., Methods: Y outh using a manual wheelchair ( n  = 60) participated in this practice-based intervention, with a waiting list period (16 weeks), exercise training (8 weeks), WMS training (8 weeks), and follow-up (16 weeks). Repeated measures included: PA (Activ8), WMS (Utrecht Pediatric Wheelchair Mobility Skills Test), confidence in wheelchair mobility (Wheelchair Mobility Confidence Scale), and physical fitness (cardiorespiratory fitness, (an)aerobic performance) and were analysed per outcome parameter using a multilevel model analyses. Differences between the waiting list and training period were determined with an unpaired sample t -test., Results: Multilevel model analysis showed significant positive effects for PA ( p  = 0.01), WMS ( p  < 0.001), confidence in wheelchair mobility ( p  < 0.001), aerobic ( p  < 0.001), and anaerobic performance ( p  < 0.001). Unpaired sample t -tests underscored these effects for PA ( p  < 0.01) and WMS ( p  < 0.001). There were no effects on cardiorespiratory fitness. The order of training (exercise before WMS) had a significant effect on confidence in wheelchair mobility., Conclusions: A combination of exercise and WMS training appears to have significant positive long-term effects on PA, WMS, confidence in wheelchair mobility, and (an)aerobic performance in youth using a manual wheelchair.Implications for rehabilitationExercise training and wheelchair mobility skills (WMS) training can lead to a sustained improvement in physical activity (PA) in youth using a manual wheelchair.These combined trainings can also lead to a sustained increase in WMS, confidence in wheelchair mobility, and (an)aerobic performance.More attention is needed in clinical practice and in research towards improving PA in youth using a manual wheelchair.

Trunk motor control is essential for the proper functioning of the upper extremities and is an important predictor of gait capacity in children with delayed development. Early diagnosis and intervention could increase the trunk motor capabilities in later life, but current tools used to assess the level of trunk motor control are largely subjective and many lack the sensitivity to accurately monitor development and the effects of therapy. Inertial measurement units could yield an objective quantitative assessment that is inexpensive and easy-to-implement. We hypothesized that root mean square of jerk, a proxy for movement smoothness, could be used to distinguish age and thereby presumed motor development. We attached a sensor to the trunks of six young children with no known developmental deficits. Root mean square of jerk decreases with age, up to 24 months, and is correlated to a more established method, i.e., center-of-pressure velocity, as well as other standard inertial measurement unit outputs. This metric therefore shows potential as a method to differentiate trunk motor control levels.

Purpose: The aim of this study was to assess the criterion validity of the Activ8 to detect "active wheelchair use" and to distinguish 6 types of wheelchair activities using video recordings as a gold standard., Methods: Ten participants who use a manual wheelchair were participants in this study. Data of 2 participants were used for adapting the algorithm and data of 7 participants were used for assessing the criterion validity., Results: Criterion validity for detecting "active wheelchair use" had a relative time difference of 7.4%, agreement of 96%, sensitivity of 98.3%, and positive predictive value of 90%. Results for distinguishing 6 types of wheelchair activities had an agreement of 73%, sensitivity of 67.1%, and positive predictive value of 65.5%., Conclusions: The Activ8 is able to detect "active wheelchair use" in youth using a manual wheelchair. Further development of the algorithm is necessary to distinguish between different types of wheelchair activities., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 Academy of Pediatric Physical Therapy of the American Physical Therapy Association.)

Purpose: Existing physical activity interventions do not reach a considerable proportion of physically disabled people. This study assessed feasibility and short-term effects of Activity Coach+, a community-based intervention especially targeting this hard-to-reach population., Methods: Feasibility was determined by reach, dropouts, and compliance with the protocol. Physical activity was measured with the Activ8 accelerometer and the adapted SQUASH questionnaire. Health outcomes were assessed by body composition, blood pressure, hand grip force, 10-metre walk test, 6-minute walk test, and the Berg Balance Scale. The RAND-36, Exercise Self-Efficacy Scale, Fatigue Severity Scale, and IMPACT-S were administered. Measurements were performed at baseline and after 2 and 4 months. Changes over time were analysed by Friedman tests., Results: Twenty-nine participants enrolled during the first 4 months, of whom two dropped out. Intervention components were employed in 86-100% of the participants. Physical activity did not change after the implementation of Activity Coach+. Body mass index ( p  = 0.006), diastolic blood pressure ( p  = 0.032), walking ability ( p  = 0.002), exercise capacity ( p  = 0.013), balance ( p  = 0.014), and vitality ( p  = 0.049) changed over time., Conclusions: Activity Coach + is feasible in a community setting. Indications for effectivity of Activity Coach + in hard-to-reach people with a physical disability were found.Implications for rehabilitationActivity Coach + was able to reach physically disabled people living in community, a population that is assumed hard-to-reach.Activity Coach + was feasible in a population of persons with a physical disability that was heterogeneous with respect to age and (severity of) disability.The current study provides the first indications for the beneficial health effects of Activity Coach + in hard-to-reach people with a physical disability.

Objectives: Physical activity is promoted in patients with hip or knee osteoarthritis (OA), yet little is known about its relationship with symptoms, functional limitations and Quality of Life (QoL). We investigated if OA-associated pain, functional limitations and QoL are associated with objectively measured physical activity in patients with end-stage hip/knee OA., Methods: Cross-sectional study including patients scheduled for primary total hip/knee arthroplasty. Patients wore an accelerometer (Activ8) with physical activity assessed over waking hours, and expressed as number of activity daily counts (ADC) per hour, %time spent on physical activity i.e. walking, cycling or running (%PA), and %time spent sedentary (%SB). Pain, functional limitations and joint-specific and general QoL were assessed with the Hip disability/Knee Injury and Osteoarthritis Outcome Score (HOOS/KOOS) and the Short Form (SF)-12. Multivariate linear regression models with the three to Z-scores transformed parameters of physical activity as dependent variables and adjusted for confounding, were conducted., Results: 49 hip and 48 knee OA patients were included. In hip and knee OA patients the mean number of ADC, %PA and %SB were 18.79 ± 7.25 and 21.19 ± 6.16, 14 ± 6.4 and 15 ± 5.0, and 66 ± 10.5 and 68 ± 8.7, respectively. In hip OA, better joint-specific and general QoL were associated with more ADC, (β 0.028; 95%CI:0.007-0.048, β0.041; 95%CI:0.010-0.071). Also, better general QoL was associated with the %PA (β 0.040, 95%CI:0.007-0.073). No other associations were found., Conclusion: Whereas QoL was associated with physical activity in hip OA, pain and functional limitations were not related to objectively measured physical activity in patients with end-stage hip or knee OA., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Introduction: To set up and guide interventions with the aim to increase physical activity and lower sedentary behavior valid monitoring of physical behavior is essential. The aim of this study was to evaluate the validity of the single-unit Activ8 activity monitor to classify several body postures and movements., Methods: Twelve healthy adults performed a series of activities, representative for everyday life, according to a standard protocol. Activ8 was both worn in the trouser pocket (prescribed location) and fixated to the front of the thigh. Activities were video recorded and analyzed thereafter. Postures and movements that were analyzed were lying/sitting, standing, walking, cycling, and running., Results: The agreement between Activ8 output and video analysis was 89.7% (inter-subject range: 66.0 to 96.6%) for the pocket location and 91.9% (range 85.5 to 95.1%) for the thigh location. Sensitivity and positive predictive value scores for both locations were all above 80%, except for standing (69% or higher). Differences in classified duration of separate postures and movements were within 20% for walking, sitting and running., Conclusion: The Activ8 is a valid instrument to quantify a defined set of body postures and movements. Because of the smaller time difference, the thigh location is preferred for research purposes., (© The Author(s) 2020.)

Objective: Botulinum toxin (BoNT-A) is widely used in combined treatment for spastic cerebral palsy, but its added value preceding comprehensive rehabilitation for motor impairments, gait, and goal attainment has not been studied., Design: A comparative multi-centre trial, in which two groups underwent comprehensive rehabilitation (i.e. high-intensive functional physiotherapy, and indicated casting/orthoses). One group received intramuscular BoNT-A prior to rehabilitation, and the other group did not receive BoNT-A., Subjects/patients: Children with spastic cerebral palsy, Gross Motor Function Classification System (GMFCS) levels I-III, age range 4-12 years, indicated for BoNT-A treatment regarding mobility problems., Methods: Sixty-five children participated (37 boys), mean age 7.3 years (standard deviation (SD) 2.3, range 4-12 years), equally distributed across GMFCS levels. Forty-one children received BoNT-A+ comprehensive rehabilitation and 24 received comprehensive rehabilitation only. Functional leg muscle strength, passive range of motion, angle of catch, cerebral palsy-related pain, walking speed, kinematic gait parameters, goal attainment, and proxy-reported general functioning were assessed at baseline, primary end-point (12 weeks) and 24-week follow-up. Statistical analyses were performed with linear mixed models., Results: At the primary end-point there were no statistically significant differences in treatment effects between the groups, except for the angle-of-catch of the rectus femoris, which was in favour of comprehensive rehabilitation without BoNT-A (12° difference, 95% confidence interval (95% CI) 2:23, p = 0.025). Results at follow-up were similar., Conclusion: At the group level, treating with BoNT-A prior to comprehensive rehabilitation did not add to the clinical effectiveness of rehabilitation. Thus, BoNT-A prescription and use should be critically reconsidered in this cerebral palsy age- and GMFCS-subgroup.

Background and Purpose: To support clinical decision-making in central neurological disorders, a physical examination is used to assess responses to passive muscle stretch. However, what exactly is being assessed is expressed and interpreted in different ways. A clear diagnostic framework is lacking. Therefore, the aim was to arrive at unambiguous terminology about the concepts and measurement around pathophysiological neuromuscular response to passive muscle stretch., Methods: During two consensus meetings, 37 experts from 12 European countries filled online questionnaires based on a Delphi approach, followed by plenary discussion after rounds. Consensus was reached for agreement ≥75%., Results: The term hyper-resistance should be used to describe the phenomenon of impaired neuromuscular response during passive stretch, instead of for example 'spasticity' or 'hypertonia'. From there, it is essential to distinguish non-neural (tissue-related) from neural (central nervous system related) contributions to hyper-resistance. Tissue contributions are elasticity, viscosity and muscle shortening. Neural contributions are velocity dependent stretch hyperreflexia and non-velocity dependent involuntary background activation. The term 'spasticity' should only be used next to stretch hyperreflexia, and 'stiffness' next to passive tissue contributions. When joint angle, moment and electromyography are recorded, components of hyper-resistance within the framework can be quantitatively assessed., Conclusions: A conceptual framework of pathophysiological responses to passive muscle stretch is defined. This framework can be used in clinical assessment of hyper-resistance and will improve communication between clinicians. Components within the framework are defined by objective parameters from instrumented assessment. These parameters need experimental validation in order to develop treatment algorithms based on the aetiology of the clinical phenomena., (© 2017 EAN.)

Objectives: Anterior Cruciate Ligament (ACL) deficiency may result in abnormal lower limb loading with increased foot pronation. This study evaluated spatiotemporal parameters and plantar pressure distribution during walking in participants with and without an ACL rupture., Design: Cross-sectional., Methods: Plantar pressure was measured in 42 unilateral ACL deficient (ACLD) participants and 32 healthy controls while walking barefoot. Spatiotemporal parameters, pressure distribution and center of pressure (CoP) during foot roll off were determined. Differences in spatiotemporal parameters and pressure distribution were analyzed using a Linear Mixed Model. CoP position was analyzed with one-way ANOVA., Results: ACLD participants had a longer contact time and earlier forefoot contact compared to controls. The ACLD side showed a shorter contact time and a faster roll off toward the forefoot compared to the ACL intact side. Compared to controls, ACLD participants had increased pressure under the medioproximal side of the midfoot. Within ACLD participants, the ACLD side had decreased pressure under the heel and increased pressure under the forefoot. Foot pronation was not different between groups or within ACLD participants. CoP of the ACLD participants was significantly more toward the toes during initial contact and toward the heel during foot flat., Conclusions: Changes in lower limb loading during barefoot walking in ACLD participants are due to changes in roll off pattern, most likely in order to reduce anterior shear forces on the knee. Dynamic plantar pressure measurements may assist in evaluating and guiding interventions aimed at normalizing lower limb and knee biomechanics in ACL deficiency., (Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Objectives: To describe the course of walking behaviour over a period of 1 year after stroke, using accelerometry, and to compare 1-year data with those from a healthy group., Design: One-year follow-up cohort study., Subjects: Twenty-three stroke patients and 20 age-matched healthy subjects., Methods: Accelerometer assessments were made in the participants' daily environment for 8 h/day during the 1st (T1), 12th (T2) and 48th (T3) weeks after stroke, and at one time-point in healthy subjects. Primary outcomes were: percentage of time walking and upright (amount); mean duration and number of walking periods (distribution); step regularity and gait symmetry (quality); and walking speed., Results: Time walking, time upright, and number of walking bouts increased during T1 and T2 (p < 0.01) and then levelled off (p > 0.30). Mean duration of walking periods showed no significant improvements (p > 0.30) during all phases. Step regularity, gait symmetry and gait speed showed a tendency to increase consistently from T1 to T3. At T3, amount and distribution variables reached the level of the healthy group, but significant differences remained (p < 0.02) in step regularity and gait speed., Conclusion: In this cohort, different outcomes of walking behaviour showed different patterns and levels of recovery, which supports the multi-dimensional character of gait.

This study assessed whether self-propelled wheelchair driving can be validly detected by a new method using a set of two commonly used accelerometers.In a rehabilitation centre, 10 wheelchair-bound persons with spinal cord injury (SCI) (aged 29-63 years) performed a series of representative daily activities according to a protocol including self-propelled wheelchair driving and other activities. Two ActiGraph GT3X+ accelerometers were used; one was attached at the wrist, the other to the spokes of the wheelchair wheel. Based on the movement intensity of the two accelerometers, a custom-made algorithm in MatLab differentiated between self-propelled wheelchair driving and other activities (e.g. being pushed or arm movements not related to wheelchair driving). Video recordings were used for reference. Validity scores between the accelerometer output and the video analyses were expressed in terms of agreement, sensitivity and specificity scores.Overall agreement for the detection of self-propelled wheelchair driving was 85%; sensitivity was 88% and specificity 83%. Disagreement between accelerometer output and video analysis was largest for wheelchair driving at very low speed on a treadmill, wheelchair driving on a slope on a treadmill, and being pushed in the wheelchair whilst making excessive arm movements.Valid detection of self-propelled wheelchair driving is provided by two accelerometers and a simple algorithm. Disagreement with the video analysis was largest during three atypical daily activities.

Physical whole-body vibration (WBV) exercises become available at various levels of intensity. In a first series of measurements, we investigated 3-dimensional platform accelerations of three different WBV devices without and with three volunteers of different weight (62, 81 and 100 kg) in squat position (150 degrees knee flexion). The devices tested were two professional devices, the PowerPlate and the Galileo-Fitness, and one home-use device, the PowerMaxx. In a second series of measurements, the transmission of vertical platform accelerations of each device to the lower limbs was tested in eight healthy volunteers in squat position (100 degrees knee flexion). The first series showed that the platforms of two professional devices vibrated in an almost perfect vertical sine wave at frequencies between 25-50 and 5-40 Hz, respectively. The platform accelerations were slightly influenced by body weight. The PowerMaxx platform mainly vibrated in the horizontal plane at frequencies between 22 and 32 Hz, with minimal accelerations in the vertical direction. The weight of the volunteers reduced the platform accelerations in the horizontal plane but amplified those in the vertical direction about eight times. The vertical accelerations were highest in the Galileo (approximately 15 units of g) and the PowerPlate (approximately 8 units of g) and lowest in the PowerMaxx (approximately 2 units of g). The second series showed that the transmission of vertical accelerations at a common preset vibration frequency of 25 Hz were largest in the ankle and that transmission of acceleration reduced approximately 10 times at the knee and hip. We conclude that large variation in 3-dimensional accelerations exist in commercially available devices. The results suggest that these differences in mechanical behaviour induce variations in transmissibility of vertical vibrations to the (lower) body.

Objective measurement of weight bearing during a long-term period can give insight into the postoperative loading of the lower extremity of orthopedic patients to avoid complications. This study investigated the validity of vertical ground reaction force measurements during a long-term period using the Pedar Mobile insole pressure system, by comparing it with a Kistler force platform. In addition, the validity of a new sensor drift correction algorithm to correct for offset drift in the Pedar signal was evaluated. Ground reaction force data were collected during dynamic and static conditions from five healthy subjects every hour for 7 h. A mean offset drift of 14.6% was found after 7 h. After applying the drift correction algorithm the Pedar system showed a high accuracy for the second peak in the ground reaction force-time curve (1.1 to 3.4% difference, p>0.05) and step duration (-2.0 to 4.4% difference, p>0.05). Less accuracy was found for the first peak in the ground reaction force-time curve (5.2 to 12.0% difference; p<0.05 for the first 3 h, p>0.05 for the last 4 h) and, consequently, in the vertical force impulse (5.5 to 11.0% difference, p>0.05). The Pedar Mobile system appeared to be a valid instrument to measure the vertical force during a long-term period when using the drift correction program described in this study.

Piezoresistive accelerometer signals are frequently used in movement analysis. However, their use and interpretation are complicated by the fact that the signal is composed of different acceleration components. The aim of the study was to obtain insight into the components of accelerometer signals from the trunk and thigh segments during four different sit-to-stand (STS) movements (self-selected, slow, fast and fullflexion). Nine subjects performed at least six trials of each type of STS movement. Accelerometer signals from the trunk and thigh in the sagittal direction were decomposed using kinematic data obtained from an opto-electronic device. Each acceleration signal was decomposed into gravitational and inertial components, and the inertial component of the trunk was subsequently decomposed into rotational and translational components. The accelerometer signals could be reliably reconstructed: mean normalised root mean square (RMS) trunk: 6.5% (range 3-12%), mean RMS thigh: 3% (range 2-5%). The accelerometric signals were highly characteristic and repeatable. The influence of the inertial component was significant, especially on the timing of the specific event of maximum trunk flexion in the accelerometer signal. The effect of inertia was larger in the trunk signal than in the thigh signal and increased with higher speeds. The study provides insight into the acceleration signal, its components and the influence of the type of STS movement and supports its use in STS movement analysis.

Objectives: To investigate the effect of pyridostigmine on fatigue, physical performance, and muscle function in subjects with postpoliomyelitis syndrome., Methods: 67 subjects with increased fatigue and new weakness in one quadriceps muscle showing neuromuscular transmission defects, were included in a randomised, double blind, placebo controlled trial of 60 mg pyridostigmine four times a day for 14 weeks. Primary outcome was fatigue (on the "energy" category of the Nottingham health profile). Secondary outcomes included two minute walking distance and quadriceps strength and jitter. Motor unit size of the quadriceps was studied as a potential effect modifier. The primary data analysis compared the changes from baseline in the outcomes in the last week of treatment between groups., Results: 31 subjects treated with pyridostigmine and 31 subjects treated with placebo completed the trial. No significant effect of pyridostigmine was found on fatigue. The walking distance improved more in the pyridostigmine group than in the placebo group (by 7.2 m (6.0%); p<0.01). Subgroup analysis showed that a significant improvement in walking performance was only found in subjects with normal sized motor units. Quadriceps strength improved more in the pyridostigmine group than in the placebo group (by 6.7 Nm (7.2%); p = 0.15). No effect of pyridostigmine was found on jitter., Conclusions: Pyridostigmine in the prescribed dose did not reduce fatigue in subjects with postpoliomyelitis syndrome. However, it may have a limited beneficial effect on physical performance, especially in subjects with neuromuscular transmission defects in normal sized motor units.

In lifting, the abdominal muscles are thought to be activated to stabilize the spine. As a detrimental effect, they contribute to spinal compression. The existing literature is not conclusive about the biological relevance of this effect. From biological, mechanical and anatomical considerations it was hypothesised that the relative abdominal contribution to compression would be minor in the beginning of the lift, that the relative and absolute abdominal contribution to compression would rise throughout the lift, and that the obliques would contribute to a larger extent than the rectus abdominis. To investigate these hypotheses, 10 subjects lifted 0.5, 10.5 and 22.5 kg. EMG levels obtained from the rectus abdominis and the obliques were converted into force using normalized EMG, muscle potential and area values, and modulating factors for muscle length and contraction velocity. An anatomical model was applied to compute the abdominal effects on spinal compression in three consecutive phases within a lift. If expressed relative to the total spinal compression, the abdominal contribution for the three weight conditions was 7.1% (SD, 1.7), 10.4% (4.7) and 12.5% (4.4) in the begin and 21.0% (5.8), 19.0% (5.3) and 22.2% (6.6) in the end phase. Thus, the relative abdominal contribution to compression was minor in the beginning and increased towards the end. The absolute abdominal contribution was constant throughout the lift. The contributions could be retraced to the obliques rather than the rectus, while during the lift a shift in activation from the obliquus externus to internus was observed.