Umeå University's logo

Thigh muscle weakness prevails following anterior cruciate ligament (ACL) injury, as usually evaluated by peak concentric quadriceps strength. Assessment throughout the range of motion (ROM), and for antagonists may provide more comprehensive information. We evaluated angle-specific torque profiles and ratios of isokinetic thigh muscle strength in 70 individuals 23 ± 2 years post-ACL injury (44males, 46.9 ± 5.4 years); 33 treated with ACL-reconstruction (ACL-R), and 37 treated only with physiotherapy (ACL-PT), and 33 controls. Quadriceps and hamstrings torques for concentric/eccentric contractions (90°/s) and ratios between hamstrings/quadriceps strength (HQ) were compared between and within groups using inferential functional data methods. The injured ACL-R leg had lower concentric and eccentric quadriceps strength compared to non-injured leg throughout the ROM, and lower concentric (interval 70–79°) and eccentric (64–67°) quadriceps strength compared to controls. The injured ACL-PT leg showed lower eccentric quadriceps strength (53–77°) than non-injured leg and lower concentric (41–79°) and eccentric (52–81°) quadriceps and eccentric hamstrings (30–77°) strength than controls. There were no group differences for HQ-ratios. The injured ACL-R leg had higher HQ-ratio (34–37°) than non-injured leg. Angle-specific torque profiles revealed strength deficits, masked if using only peak values, and seem valuable for ACL-injury rehabilitation.     

Investigations of kinetic asymmetries during bilateral squats following anterior cruciate ligament reconstruction (ACLR) are limited to mainly cross-sectional studies and discrete value data extracted at specific knee angles. We assessed loading asymmetries during squats longitudinally throughout rehabilitation using curve analysis and compared patient-reported outcome measures (PROMs) between those with and without asymmetry. Bodyweight squats were performed by 24 individuals (13 females) post-ACLR on three occasions: (1) Early 2.9 (1.1) months; (2) Mid 8.8 (3.1) months; (3) at Return to Sport (RTS) 13.1 (3.6) months; and 29 asymptomatic controls (22 females) once. Time-normalized between-leg asymmetry curves of sagittal plane hip, knee, and ankle moments and vertical ground reaction forces were compared using functional data analysis methods. Individual asymmetrical loading for ACLR was classified when exceeding the 95% confidence interval of controls during ≥50% of the squat. At Early, ACLR had greater asymmetry than controls for knee (15%–100% eccentric phase; 0%–100% concentric) and ankle flexion moments (56%–65% concentric). At Mid, ACLR had greater asymmetry for knee (41%–72% eccentric) and ankle flexion moments (56%–69% concentric). No between-group differences were found at RTS. From Early to RTS, ACLR reduced asymmetry for hip (21%–46% eccentric), knee (27%–58% concentric), and ankle flexion moments (21%–57% eccentric). At Early, 11/24 underloaded their ACLR knee and 1 overloaded compared with controls. At RTS, 4 underloaded and 6 overloaded. No differences in PROMs were found based on loading asymmetry. Beyond the early phase of rehabilitation from ACLR, individual-level analyses are required to reveal differing loading strategies during bilateral squats.

This article presents methods to study the causal effect of a binary treatment on a functional outcome with observational data. We define a Functional Average Treatment Effect (FATE) and develop an outcome regression estimator. We show how to obtain valid inference on the FATE using simultaneous confidence bands, which cover the FATE with a given probability over the entire domain. Simulation experiments illustrate how the simultaneous confidence bands take the multiple comparison problem into account. Finally, we use the methods to infer the effect of early adult location on subsequent income development for one Swedish birth cohort.

Evaluating test–retest reliability is crucial in biomechanical research, as it validates experimental results. While methods for reliability of scalar outcome variables are well-established, methods to assess reliability of continuous curve data (such as joint angle trajectories during gait) remain less explored. This study investigates methods for constructing confidence sets for curve-level intraclass correlation coefficients (ICC), which can be expressed as either an ICC curve or an integrated ICC. Currently, no standardised guidelines exist in biomechanics for reporting curve-level ICC uncertainty. Nonparametric bootstrapping techniques are proposed for both the ICC curve's confidence bands and the integrated ICC's confidence intervals, and these methods are validated through Monte Carlo simulations, covering various effect sizes and curve characteristics. Additionally, these methods are applied to assess the test–retest reliability of knee kinematics in three different planes during landing of one-leg hops, where less uncertainty is observed for the ICC curve and integrated ICC in the frontal plane compared to other planes. When the entire time domain is of primary empirical interest, we recommend using a rank-based bootstrap confidence band to express ICC uncertainty, as it yields increasingly precise and valid results as the number of individuals increases, with the coverage rate approaching the correct level of 95%. When a single summary metric is of primary interest, we recommend using the integrated ICC along with a typical bootstrap confidence interval based on the normal distribution, as the coverage rate remains adequately accurate and stable at around the correct level of 95% across varying number of individuals.

Inom de flesta utbildningar förväntas studenter lära sig behärska såväl akademiskt som yrkesmässigt skrivande, så även inom Programmet i statistik och data science, 180 hp. Som lärare på detta program har vi upplevt att många studenter har svårt med alla former av skrivande. Vår egen kunskap om skrivande baseras enbart på erfarenheter från vårt eget skrivande i ämnet, både inom utbildning och forskning. Vi har därför i vissa avseenden känt oss begränsade i vårt arbete kopplat till studenters skrivande. Under våren 2023 deltog vi därför i projektet SKRIVUM vid Umeå universitet. SKRIVUM har som syfte att stärka universitetslärares skrivdidaktiska ämneskompetens genom att utforska och utveckla det ämnesintegrerade skrivandet inom programmen, med akademisk litteracitet (Wingate, 2018) som teoretisk utgångspunkt.  

Under åtta verkstäder arbetade vi kollegialt med kartläggning av akademiskt och yrkesmässigt skrivande inom Programmet i statistik och data science. Vi fokuserade på kursernas förväntade studieresultat (lärandemål), examinationsuppgifter samt stöd och stöttning kopplade till skrivande. Med kartläggningen som utgångspunkt identifierade vi två mål för vårt fortsatta arbete. Det primära målet är att utveckla och implementera konkreta ”verktyg” som stödjer studenternas akademiska och yrkesmässiga skrivande. Det sekundära målet är att öka samsynen inom kollegiet kring hur vi kan och bör arbeta med detta. De förändringar vi föreslår ska i huvudsak rymmas inom ramen för verksamhetens befintliga resurstilldelning. 

Ett första konkret ”verktyg” för att stödja studenterna har redan utvecklats och implementerats. Verktyget är en modelltext för dataanalysrapporter. Modelltexten användes av studenter för första gången höstterminen 2023 som en förebild för deras rapportskrivande. Modelltexten introducerades till studenterna genom en verkstad där vi tillsammans identifierade modelltextens struktur, stil, innehåll samt dess ämnesspecifika kännetecken. En reviderad modelltext baserad på både lärarnas och studenternas utvärdering av modelltexten planeras att användas under vårterminen 2024.  

För att uppnå samsyn inom kollegiet planeras en studiecirkel kring boken Communicating with data: The art of writing for data science (Nolan och Stoudt, 2021) under vårterminen 2024. Dessutom presenteras och tillgängliggörs de ”verktyg” som utarbetas, så att de kan användas av hela kollegiet.  

Vi kommer att delge våra erfarenheter från tiden efter SKRIVUM, med huvudfokus på det kollegiala arbetet med modelltexten samt hur den har implementerats och använts för att stödja studenternas akademiska och yrkesmässiga skrivande.  

Referenser: 

Nolan, D., & Stoudt, S. (2021). Communicating with data: The art of writing for data science. Oxford University Press.  

Wingate, U. (2018). Academic literacy across the curriculum: Towards a collaborative instructional approach. Language Teaching, 51(3), 349-364.  

Background: Kinematic studies suggest that injury of the anterior cruciate ligament (ACL) leads to long-lasting movement deficits or compensations to unload the injured knee. This study evaluated lower body kinematics during squats in individuals who suffered unilateral ACL-injury more than 20 years ago.

Method: Using motion capture, we compared maximum squat depth, time to complete the squat task, detailed kinematics, estimated kinetic-chain joint moments 0- 80° knee flexion, and weight distribution between legs across three groups with (ACL_R, n = 27) and without ACL-reconstructive surgery (ACL_PT, physiotherapy only, n = 28), and age-matched non-injured asymptomatic Controls (n = 31, average age across groups 47 years).

Results: ACL_PT demonstrated significantly reduced squat depth compared to Controls (p = 0.004), whereas ACL_R performed similarly to Controls (p = 1.000). Other outcome variables were comparable between groups. All participants nevertheless demonstrated asymmetric weight distribution between legs but without systematic unloading of the injured side in the ACLgroups.

Conclusion: Expected compensatory strategies were not found in the ACL-groups, while poorer squat performance in the ACL-deficient group may depend on pure knee-joint mechanics, or lifestyle factors attributed to a less stable knee decades after ACL-injury.

Functional data are smooth, often continuous, random curves, which can be seen as an extreme case of multivariate data with infinite dimensionality. Just as component-wise inference for multivariate data naturally performs feature selection, subset-wise inference for functional data performs domain selection. In this paper, we present a unified testing framework for domain selection on populations of functional data. In detail, p-values of hypothesis tests performed on point-wise evaluations of functional data are suitably adjusted for providing a control of the family-wise error rate (FWER) over a family of subsets of the domain. We show that several state-of-the-art domain selection methods fit within this framework and differ from each other by the choice of the family over which the control of the FWER is provided. In the existing literature, these families are always defined a priori. In this work, we also propose a novel approach, coined threshold-wise testing, in which the family of subsets is instead built in a data-driven fashion. The method seamlessly generalizes to multidimensional domains in contrast to methods based on a-priori defined families. We provide theoretical results with respect to consistency and control of the FWER for the methods within the unified framework. We illustrate the performance of the methods within the unified framework on simulated and real data examples, and compare their performance with other existing methods.

The recent sports science literature conveys a growing interest in robust statistical methods to analyze smooth, regularly-sampled functional data. This paper focuses on the inferential problem of identifying the parts of a functional domain where two population means differ. We considered four approaches recently used in sports science: interval-wise testing (IWT), statistical parametric mapping (SPM), statistical nonparametric mapping (SnPM) and the Benjamini-Hochberg (BH) procedure for false discovery control. We applied these procedures to both six representative sports science datasets, and also to systematically varied simulated datasets which replicated ten signal- and/or noise-relevant parameters that were identified in the experimental datasets. We observed generally higher IWT and BH sensitivity for five of the six experimental datasets. BH was the most sensitive procedure in simulation, but also had relatively high false positive rates (generally > 0.1) which increased sharply (> 0.3) in certain extreme simulation scenarios including highly rough data. SPM and SnPM were more sensitive than IWT in simulation except for (1) high roughness, (2) high nonstationarity, and (3) highly nonuniform smoothness. These results suggest that the optimum procedure is both signal and noise-dependent. We conclude that: (1) BH is most sensitive but also susceptible to high false positive rates, (2) IWT, SPM and SnPM appear to have relatively inconsequential differences in terms of domain identification sensitivity, except in cases of extreme signal/noise characteristics, where IWT appears to be superior at identifying a greater portion of the true signal.

INTRODUCTION: Kinetic loading asymmetries during bilateral squats have been reported following anterior cruciate ligament reconstruction (ACLR). Evidence is however limited to discrete value data extracted at specific knee angles from cross-sectional studies where side-toside strategies are presented only at group level. It is therefore unclear whether loading asymmetries occur throughout the entire squat, whether they change during rehabilitation and how they are distributed between sides.

METHODS: Bilateral bodyweight squats were performed by 24 individuals (13 females) post-ACLR on three occasions: 1) Early rehab - 2.9(1.1) months; 2) Mid-rehab - 8.8 (3.1) months; 3) Return to sport (RTS) - 13.1 (3.6) months; and 29 asymptomatic controls (22 females) on one occasion. Motion capture and two force plates were used to calculate time-normalized curves of vertical ground reaction forces andhip, knee, and ankle moments. Outcomes were compared between sides and groups, and over time, using functional t-tests with p-values adjusted by the interval-wise testing procedure. Individual knee loading strategies, i.e., under-/overloading of the ACLR side, were classified when asymmetry in favour of the respective side exceeded the 95% pointwise confidence interval of controls during at least 50% of the squat.

RESULTS: At Early rehab, ACLR had significantly greater (adjusted P < .05) asymmetry in knee flexion moment than controls during thetime-normalized interval of 15-100% of the eccentric phase and the entire concentric phase, as well as ankle flexion moment during 56-65% of the concentric phase. At Mid-rehab, ACLR had significantly greater asymmetry than controls for knee flexion moment during 41-72% of the eccentric phase and for ankle flexion moment during 56-69% of the concentric phase. No significant between-group differences were found at RTS. At RTS compared with Early rehab, ACLR significantly reduced asymmetry for hip (21-46%, eccentric phase), knee (27-58%, concentric phase), and ankle flexion moment (21-57%, eccentric phase). Individual asymmetry strategies for knee flexion moment atEarly rehab were mainly due to individuals underloading the ACLR side (46%) rather than overloading (4%). At RTS, however, more individuals overloaded (25%) than underloaded (17%) the ACLR side.

CONCLUSION: Curve analyses revealed significant kinetic loading asymmetries throughout bilateral bodyweight squats for our ACLR group compared with controls at Early rehab and Mid-rehab, but not at RTS. Significant reductions in hip, knee and ankle flexion moment asymmetry from Early rehab to RTS showed modifications during rehabilitation. An expected underloading strategy was evident for almost half of the ACLR participants at Early rehab, but an overloading strategy was the main reason for knee flexion moment asymmetry at RTS.Loading asymmetries during bilateral tasks should thus not be assumed due to underloading of the ACLR side, but may depend on anoverloading strategy, particularly late in rehabilitation.

Background: An anterior cruciate ligament (ACL) rupture may result in poor sensorimotor knee control and, consequentially, adapted movement strategies to help maintain knee stability. Whether patients display atypical lower limb mechanics during weight acceptance of stair descent at different time frames after ACL reconstruction (ACLR) is unknown.

Purpose:To compare the presence of atypical lower limb mechanics during the weight acceptance phase of stair descent among athletes at early, middle, and late time frames after unilateral ACLR.

Study Design:Controlled laboratory study.

Methods:A total of 49 athletes with ACLR were classified into 3 groups according to time after ACLR—early (<6 months; n = 17), middle (6-18 months; n = 16), and late (>18 months; n = 16)—and compared with asymptomatic athletes (control; n = 18). Sagittal plane hip, knee, and ankle angles; angular velocities; moments; and powers were compared between the ACLR groups’ injured and noninjured legs and the control group as well as between legs within groups using functional data analysis methods.

Results:All 3 ACLR groups showed greater knee flexion angles and moments than the control group for injured and noninjured legs. For the other outcomes, the early group had, compared with the control group, less hip power absorption, more knee power absorption, lower ankle plantarflexion angle, lower ankle dorsiflexion moment, and less ankle power absorption for the injured leg and more knee power absorption and higher vertical ground reaction force for the noninjured leg. In addition, the late group showed differences from the control group for the injured leg revealing more knee power absorption and lower ankle plantarflexion angle. Only the early group took a longer time than the control group to complete weight acceptance and demonstrated asymmetry for multiple outcomes.

Conclusion:Athletes with different time frames after ACLR revealed atypically large knee angles and moments during weight acceptance of stair descent for both the injured and the noninjured legs. These findings may express a chronically adapted strategy to increase knee control. In contrast, atypical hip and ankle mechanics seem restricted to an early time frame after ACLR.

Clinical Relevance:Rehabilitation after ACLR should include early training in controlling weight acceptance. Including a control group is essential when evaluating movement patterns after ACLR because both legs may be affected.