Search

Background: Aging is associated with slowed gait and old compared with young adults generally walk with greater positive hip work (H1) and reduced positive ankle work (A2). The role of exercise interventions on old adults' gait mechanics that underlie training-induced improvements in gait velocity is unclear. We examined the effects of lower extremity power training and detraining on old adults' gait kinetics.Methods: As part of the Potsdam Gait Study (POGS), healthy old adults completed a no-intervention control period (69.1±4.4yrs, n=14) or a power training program followed by detraining (72.9±5.4yrs, n=15). We measured isokinetic knee extensor and plantarflexor power and measured hip, knee and ankle kinetics at habitual, fast and standardized walking speeds.Results: Power training significantly increased isokinetic knee extensor power (25%), plantarflexor power (43%), and fast gait velocity (5.9%). Gait mechanics underlying the improved fast gait velocity included increases in hip angular impulse (29%) and H1 work (37%) and no changes in positive knee (K2) and A2 work. Detraining further improved fast gait velocity (4.7%) with reductions in H1 (-35%), and increases in K2 (36%) and A2 (7%).Conclusion: Power training increased fast gait velocity in healthy old adults by increasing the reliance on hip muscle function and thus further strengthened the age-related distal-to-proximal shift in muscle function. [ABSTRACT FROM AUTHOR]

Introduction: Slow gait predicts many adverse clinical outcomes in old adults, but the mechanisms of how power training can minimize the age-related loss of gait velocity is unclear. We examined the effects of 10 wk of lower extremity power training and detraining on healthy old adults' lower extremity muscle power and gait kinematics. Methods: As part of the Potsdam Gait Study, participants started with 10 wk of power training followed by 10 wk of detraining (n = 16), and participants started with a 10-wk control period followed by 10 wk of power training (n = 16). We measured gait kinematics (stride characteristic and joint kinematics) and isokinetic power of the ankle plantarflexor (20°⋅s-1, 40°⋅s-1, and 60°⋅s-1) and knee extensor and flexor (60°⋅s-1,120°⋅s-1, and 180°⋅s-1) muscles at weeks 0,10, and 20. Results: Power training improved isokinetic muscle power by ~30% (P < 0.001) and fast (5.9%, P < 0.05) but not habitual gait velocity. Ankle plantarflexor velocity measured during gait at fast pace decreased by 7.9% (P < 0.05). The changes isokinetic muscle power and joint kinematics did not correlate with increases in fast gait velocity. The mechanisms that increased fast gait velocity involved higher cadence (r = 0.86, P < 0.001) rather than longer strides (r = 0.49, P = 0.066). Detraining did not reverse the training-induced increases in muscle power and fast gait velocity. Conclusion: Because increases in muscle power and modifications in joint kinematics did not correlate with increases in fast gait velocity, kinematic mechanisms seem to play a minor role in improving healthy old adults' fast gait velocity after power training. [ABSTRACT FROM AUTHOR]

Purpose: Old compared with young adults walk with reduced ankle and increased hip mechanical output. We examined the idea that age, leg strength, or both are related to the age-related changes in mechanical output during gait.Methods: Healthy young (n = 32, age 21.5 years) and old adults (n = 32, age 76.8 years) participated in biomechanical gait analyses at 1.5 m/s and were also measured for maximal leg strength.Results: Analysis 1 confirmed previous data as old compared with young adults walked with 50 % more hip positive work and 18 % less ankle positive work. Analysis 2 showed that leg strength did not affect gait kinetics in groups of subjects with similar ages. In a weak young and a strong old group, Analysis 3 showed that old adults still walked with 23 % greater hip positive work. The group by joint interaction in Analysis 4 was suggestive of an even greater reliance on hip and less reliance on ankle work in weak compared with strong old adults.Conclusions: Age and leg strength both contribute to the age-related changes in mechanical output during gait. Exercise prescription, normally targeting the knee extensors, should also involve ankle and hip muscles. [ABSTRACT FROM AUTHOR]

Magnetic resonance and ultrasound imaging have shown hamstring strain injuries occur most often in the biceps femoris long head (BFLH), and particularly in the proximal vs. distal region of this muscle. Animal research and musculoskeletal modeling (MSK) have detected heterogeneous fascicle behavior within muscle regions, and within fascicles. Understanding architectural behavior differences during muscle contractions may help to discern possible mechanisms behind proximal BFLH injuries. The purpose of our study was to assess the magnitude of shortening of the proximal and distal fascicles of the BFLH under a range of muscle activation levels under isometric conditions using ultrasound imaging (US). Thirteen healthy adults performed targeted sustained isometric contractions while US were taken of the entire BFLH. Measurements of fascicle lengths in both muscle regions were compared at 20%, 30%, 50%, and 67% MVIC. The results showed that while both regions shortened significantly with activation, the proximal fascicles were significantly longer, regardless of activation level (∼38%), and shortened significantly more than the distal fascicles overall (∼40%), and cumulatively at higher activation levels (30% and above). No significant strain differences were found between the two regions. These data suggest heterogeneous fascicle behavior exists in an absolute sense; however, differences in behavior are eliminated when normalized (strain). Coupled with MSK literature, the absence of regional fascicle strain differences in this study may indicate strain heterogeneity is not detectable at the whole fascicle level. Further knowledge of this commonly strained muscle's regional behavior during dynamic movements could provide evidence of proximal hamstring strain predisposition. [ABSTRACT FROM AUTHOR]

Purpose: Using three separate models that included total body mass, total lean and total fat mass, and abdominal and thigh fat as independent measures, we determined their association with knee joint loads in older overweight and obese adults with knee osteoarthritis (OA). Methods: Fat depots were quantified using computed tomography, and total lean and fat mass were determined with dual energy x-ray absorptiometry in 176 adults (age, 66.3 yr; body mass index, 33.5 kg•m−2) with radiographic knee OA. Knee moments and joint bone-on-bone forces were calculated using gait analysis and musculoskeletal modeling. Results: Higher total body mass was significantly associated (P ≤ 0.0001) with greater knee compressive and shear forces, compressive and shear impulses (P < 0.0001), patellofemoral forces (P < 0.006), and knee extensor moments (P = 0.003). Regression analysis with total lean and total fat mass as independent variables revealed significant positive associations of total fat mass with knee compressive (P = 0.0001), shear (P < 0.001), and patellofemoral forces (P = 0.01) and knee extension moment (P = 0.008). Gastrocnemius and quadriceps forces were positively associated with total fat mass. Total lean mass was associated with knee compressive force (P = 0.002). A regression model that included total thigh and total abdominal fat found that both were significantly associated with knee compressive and shear forces (P ≤ 0.04). Thigh fat was associated with knee abduction (P = 0.03) and knee extension moment (P = 0.02). Conclusions: Thigh fat, consisting predominately of subcutaneous fat, had similar significant associations with knee joint forces as abdominal fat despite its much smaller volume and could be an important therapeutic target for people with knee OA. [ABSTRACT FROM AUTHOR]

Importance: Knee osteoarthritis (OA), a common cause of chronic pain and disability, has biomechanical and inflammatory origins and is exacerbated by obesity.Objective: To determine whether a ≥10% reduction in body weight induced by diet, with or without exercise, would improve mechanistic and clinical outcomes more than exercise alone.Design, Setting, and Participants: Single-blind, 18-month, randomized clinical trial at Wake Forest University between July 2006 and April 2011. The diet and exercise interventions were center-based with options for the exercise groups to transition to a home-based program. Participants were 454 overweight and obese older community-dwelling adults (age ≥55 years with body mass index of 27-41) with pain and radiographic knee OA.Interventions: Intensive diet-induced weight loss plus exercise, intensive diet-induced weight loss, or exercise.Main Outcomes and Measures: Mechanistic primary outcomes: knee joint compressive force and plasma IL-6 levels; secondary clinical outcomes: self-reported pain (range, 0-20), function (range, 0-68), mobility, and health-related quality of life (range, 0-100).Results: Three hundred ninety-nine participants (88%) completed the study. Mean weight loss for diet + exercise participants was 10.6 kg (11.4%); for the diet group, 8.9 kg (9.5%); and for the exercise group, 1.8 kg (2.0%). After 18 months, knee compressive forces were lower in diet participants (mean, 2487 N; 95% CI, 2393 to 2581) compared with exercise participants (2687 N; 95% CI, 2590 to 2784, pairwise difference [Δ](exercise vs diet )= 200 N; 95% CI, 55 to 345; P = .007). Concentrations of IL-6 were lower in diet + exercise (2.7 pg/mL; 95% CI, 2.5 to 3.0) and diet participants (2.7 pg/mL; 95% CI, 2.4 to 3.0) compared with exercise participants (3.1 pg/mL; 95% CI, 2.9 to 3.4; Δ(exercise vs diet + exercise) = 0.39 pg/mL; 95% CI, -0.03 to 0.81; P = .007; Δ(exercise vs diet )= 0.43 pg/mL; 95% CI, 0.01 to 0.85, P = .006). The diet + exercise group had less pain (3.6; 95% CI, 3.2 to 4.1) and better function (14.1; 95% CI, 12.6 to 15.6) than both the diet group (4.8; 95% CI, 4.3 to 5.2) and exercise group (4.7; 95% CI, 4.2 to 5.1, Δ(exercise vs diet + exercise) = 1.02; 95% CI, 0.33 to 1.71; P(pain) = .004; 18.4; 95% CI, 16.9 to 19.9; Δ(exercise vs diet + exercise), 4.29; 95% CI, 2.07 to 6.50; P(function )< .001). The diet + exercise group (44.7; 95% CI, 43.4 to 46.0) also had better physical health-related quality of life scores than the exercise group (41.9; 95% CI, 40.5 to 43.2; Δ(exercise vs diet + exercise) = -2.81; 95% CI, -4.76 to -0.86; P = .005).Conclusions and Relevance: Among overweight and obese adults with knee OA, after 18 months, participants in the diet + exercise and diet groups had more weight loss and greater reductions in IL-6 levels than those in the exercise group; those in the diet group had greater reductions in knee compressive force than those in the exercise group.Trial Registration: clinicaltrials.gov Identifier: NCT00381290. [ABSTRACT FROM AUTHOR]

Background. The net metabolic cost of walking (Cw) as well as the level of neural activation of agonist and antagonist leg muscles are higher in healthy old compared with young adults. This study examined the association between Cw and agonist muscle activity and antagonist coactivity in young and old adults. Methods. Young and old adults walked at 0.98 m/s on a treadmill set at 6% decline, level, and 6% incline, while Cw and neural activation of leg muscles were measured. Results. Cw was 7.0% (incline), 19.2% (level), and 47.3% (decline) higher in old adults (overall 18.3%). Old (67.1%) versus young (40.1%) adults activated their leg muscles 67.3% more during the gait tasks and had 152.8% higher antagonist muscle coactivation (old: 67.1%, young: 19.9%). Agonist muscle activation was unrelated to Cw on incline, but it explained up to 42% (level), 48% (decline), and 70% (three tasks combined) of variance in Cw. Antagonist coactivation accounted for up to 41% (incline), 45% (level), 59% (decline), 39% (three tasks combined) of variance in Cw. Conclusions. Age-related adaptations in the recruitment pattern of leg muscles during gait significantly contribute to the high Cw in old adults. Clinical interventions optimizing the neural control of leg muscles during gait could reduce Cw consequently the relative effort needed for exercise and activities of daily living in old adults. [ABSTRACT FROM PUBLISHER]

Unilateral lengthening contractions provide a greater stimulus for neuromuscular adaptation than shortening contractions in the active and non-active contralateral homologous muscle, although little is known of the potential mechanism. Here we examined the possibility that corticospinal and spinal excitability vary in a contraction-specific manner in the relaxed right flexor carpi radialis (FCR) when humans perform unilateral lengthening and shortening contractions of the left wrist flexors at the same absolute force. Corticospinal excitability in the relaxed right FCR increased more during lengthening than shortening at 80% and 100% of maximum voluntary contraction (MVC). Short-interval intracortical inhibition diminished during shortening contractions, and it became nearly abolished during lengthening. Intracortical facilitation lessened during shortening but increased during lengthening. Interhemispheric inhibition to the 'non-active' motor cortex diminished during shortening, and became nearly abolished during lengthening at 90% MVC. The amplitude of the Hoffman reflex in the relaxed right FCR decreased during and remained depressed for 20 s after lengthening and shortening of the left wrist flexors. We discuss the possibility that instead of the increased afferent input, differences in the descending motor command and activation of brain areas that link function of the motor cortices during muscle lengthening vs. shortening may cause the contraction-specific modulation of ipsilateral motor cortical output. In conclusion, ipsilateral motor cortex responses to transcranial magnetic stimulation are contraction-specific; unilateral lengthening and shortening contractions reduced contralateral spinal excitability, but uniquely modulated ipsilateral corticospinal excitability and the networks involved in intracortical and interhemispheric connections, which may have clinical implications. [ABSTRACT FROM AUTHOR]

Accurate identification of the onset of muscle activity is an important element in the biomechanical analysis of human movement. The purpose of this study was to determine if inclusion of the Teager-Kaiser energy operator (TKEO) in signal conditioning would increase the accuracy of popular electromyography (EMG) onset detection methods. Three methods, visual determination, threshold-based method, and approximated generalized likelihood ratio were used to estimate the onset of EMG burst with and without TKEO conditioning. Reference signals, with known onset times, were constructed from EMG signals collected during isometric contraction of the vastus lateralis (n = 17). Additionally, vastus lateralis EMG signals (n = 255) recorded during gait were used to evaluate a clinical application of the TKEO conditioning. Inclusion of TKEO in signal conditioning significantly reduced mean detection error of all three methods compared with signal conditioning without TKEO, using artificially generated reference data (13 vs. 98 ms, p < 0.001) and also compared with experimental data collected during gait (55 vs. 124 ms, p < 0.001). In conclusion, addition of TKEO as a step in conditioning surface EMG signals increases the detection accuracy of EMG burst boundaries. [ABSTRACT FROM AUTHOR]

Abstract: Old adults execute single-joint voluntary movements with heightened antagonist muscle coactivation and altered timing between agonist and antagonist muscles. It is less clear if old adults adopt similar strategies during the most common form of activity of daily living, gait, and if age and gait velocity interact. We compared antagonist muscle activation amplitude and onset, offset, and activation duration of the vastus lateralis, biceps femoris, tibialis anterior, and gastrocnemius lateralis from surface EMG in 17 young (age 19–25) and 17 old adults (age 71–85) while walking at 1.2, 1.5, and 1.8m/s. All participants were healthy and highly mobile. The activation level of the four muscles when each acted as the antagonist was, on the average, 83% higher in old vs young adults (for each muscle p <0.05). In two of four muscles this activation increased with gait velocity in young but not in old adults. The inter-burst interval between TA and GL was two-fold (83ms) longer in young vs old adults and at higher gait velocities it became 14% (24ms) shorter in young but 51% (31ms) longer in old adults (interaction, p =0.015). It is concluded that there is an interaction between age and gait velocity in the amplitude and timing of antagonist muscle coactivation. [Copyright &y& Elsevier]

Abstract: Although both trunk mass and trunk position have the potential to affect lower extremity biomechanics during landing, these effects are not well understood. Our overall hypothesis stated that both trunk mass and trunk position affect lower extremity biomechanics in landing. Thus, our purpose was to determine the effects of an added trunk load and kinematic trunk adaptation groups on lower extremity joint kinematics, kinetics, and energetics during drop-landings. Twenty-one recreationally active subjects were instrumented for biomechanical analysis. Subjects performed two sets of eight double-limb landings with and without 10% body weight added to the trunk. On lower extremity dependent variables, 2(condition: no load, trunk load)×2(group: trunk extensors vs. trunk flexors) ANOVAs were performed. Condition by group interactions at the hip showed differing responses to the added trunk load between groups where the trunk extensor group decreased hip extensor efforts (↓11–18%) while the trunk flexor group increased hip extensor efforts (↑14–19%). The trunk load increased biomechanical demands at the knee and ankle regardless of trunk adaptation group. However, the percent increases in angular impulses and energy absorption in the trunk extensor group were 14–28% while increases in the trunk flexor group were 4–9%. Given the 10% body weight added to the trunk, the 14–28% increases at the knee and ankle in the trunk extensor group were likely due to the reduced hip extensor efforts during landing. Overall these findings support our overall hypothesis that both trunk mass and trunk position affect lower extremity biomechanics during vertically oriented landing tasks. [Copyright &y& Elsevier]

Background: Old adults' ability to execute activities of daily living (ADLs) declines with age. One possible reason for this decline is that the execution of customary motor tasks requires a substantially greater effort in old compared with young adults relative to their available maximal capacity.Methods: We tested the hypothesis that the relative effort (i.e., the percentage of joint moment relative to maximal joint moment) to execute ADLs is higher in old adults compared with young adults. Healthy young adults (n = 13; mean age, 22 years) and old adults (n = 14; mean age, 74 years) ascended and descended stairs and rose from a chair and performed maximal-effort isometric supine leg press. Using inverse dynamics analysis, we determined knee joint moments in ADLs and computed relative effort.Results: Compared with young adults, old adults had 60% lower maximal leg press moments, 53% slower knee angular velocity at peak torque, and 27% lower knee joint moments in the ADLs (all p <.05). Relative effort in ascent was 54% (SD +/- 16%) and 78% (+/-20%) in young and old adults, respectively; in descent, it was 42% (+/-20%) and 88% (+/-43%); and in chair rise, it was 42% (+/-19%) and 80% (+/-34%) (all p <.05). The relative electromyographic activity of the vastus lateralis and the coactivity of the biceps femoris associated with this relative effort were, respectively, 2- and 1.6-fold greater in old compared with young adults in the 3 ADLs (p <.05).Conclusions: For healthy old adults, the difficulty that arises while performing ADLs may be due more to working at a higher level of effort relative to their maximum capability than to the absolute functional demands imposed by the task. [ABSTRACT FROM AUTHOR]

National Biomechanics Day (NBD) is an international celebration of biomechanics that seeks to increase the awareness and appreciation of biomechanics among the high school community. Initial research supports the positive effects of NBD on students' attitudes toward the field of biomechanics; however, quantitative evidence remains scarce. The purpose of this study was to quantify changes in high school students' perceptions toward biomechanics after participating in NBD events to better understand the impact of NBD. Data were collected at two locations during the 2019 NBD season. Surveys were collected before and after NBD events for 112 high school students from Montana and North Carolina. Paired pre- versus post-NBD surveys for the aggregate sample population suggest that students perceived biomechanics as more appealing (p = 0.050), exciting (p = 0.007), and important (p = 0.018) following the NBD events. Students did not report a change in whether they could see themselves in a biomechanics-related career (p = 0.49). These findings further support the ability for NBD events to positively impact students' perceptions toward biomechanics, although opportunities persist to increase student career interest in biomechanics. This paper presents and discusses the study's results, interpretations, limitations, and implications for future research on biomechanics outreach activities. [ABSTRACT FROM AUTHOR]

The Intensive Diet and Exercise for Arthritis (IDEA) trial was an 18-month randomized controlled trial that enrolled 454 overweight and obese older adults with symptomatic and radiographic knee osteoarthritis (OA). Participants were randomized to either exercise (E), intensive diet-induced weight loss (D), or intensive diet-induced weight loss plus exercise (D + E) interventions. We previously reported that the clinical benefits of D + E were significantly greater than with either intervention alone (e.g., greater pain reduction, and better function, mobility, and health-related quality of life). We now test the hypothesis that D + E has greater overall benefit on gait mechanics compared to either intervention alone. Knee joint loading was analyzed using inverse dynamics and musculoskeletal modeling. Analysis of covariance determined the interventions' effects on gait. The D + E group walked significantly faster at 18-month follow-up (1.35 m s−1) than E (1.29 m s−1, p = 0.0004) and D (1.31 m s−1, p = 0.0007). Tibiofemoral compressive impulse was significantly lower (p = 0.0007) in D (1069 N s) and D + E (1054 N s) compared to E (1130 N s). D had significantly lower peak hip external rotation moment (p = 0.01), hip abduction moment (p = 0.0003), and peak hip power production (p = 0.016) compared with E. Peak ankle plantar flexion moment was significantly less (p < 0.0001) in the two diet groups compared with E. There also was a significant dose-response to weight loss; participants that lost >10% of baseline body weight had significantly (p = 0.0001) lower resultant knee forces and lower muscle (quadriceps, hamstring, and gastrocnemius) forces than participants that had less weight loss. Compared to E, D produces significant load reductions at the hip, knee, and ankle; combining D with E attenuates these reductions, but most remain significantly better than with E alone. [ABSTRACT FROM AUTHOR]

A joint moment also causes motion at other joints of the body. This joint coupling-perspective allows more insight into two age-related phenomena during gait. First, whether increased hip kinetic output compensates for decreased ankle kinetic output during positive joint work. Second, whether preserved joint kinetic patterns during negative joint work in older age have any functional implication. Therefore, we examined how age and surface inclination affect joint moment strategies to accelerate and/or decelerate individual leg joints during walking. Healthy young (age: 22.5 ± 4.1 years, n = 18) and older (age: 76.0 ± 5.7 years, n = 22) adults walked at 1.4 m/s on a split-belt instrumented treadmill at three grades (0%, 10%, −10%). Lower-extremity moment-induced angular accelerations were calculated for the hip (0% and 10%) and knee (0% and −10%) joints. During level and uphill walking, both age groups showed comparable ankle moment-induced ipsilateral (p = 0.774) and contralateral (p = 0.047) hip accelerations, although older adults generated lower ankle moments in late stance. However, ankle moment-induced contralateral hip accelerations were smaller (p = 0.001) in an older adult subgroup (n = 13) who showed larger hip extension moments in early stance than young adults. During level and downhill walking, leg joint moment-induced knee accelerations were unaffected by age (all p > 0.05). These findings suggest that during level and uphill walking increased hip flexor mechanical output in older adults does not arise from reduced ankle moments, contrary to increased hip extensor mechanical output. Additionally, results during level and downhill walking imply that preserved eccentric knee extensor function is important in maintaining knee stabilization in older age. [ABSTRACT FROM AUTHOR]

Skipping represents a training alternative to running due to its lower knee contact forces and higher whole-body metabolic cost. The increased metabolic cost of skipping is associated with a higher vertical center-of-mass (COM) displacement during the support and flight phases of the skipping hop compared to running. However, skipping has lower muscle force impulses than running. Therefore, the study purpose was to compare the flow of mechanical power between body segments during skipping and running to determine the mechanisms enabling higher vertical displacement in skipping despite the lower vertical impulse. Running and skipping cycles were simulated in OpenSim for 5 adults (22.4 ± 2.2 y) using motion capture data collected at 2.5 m/s on an instrumented dual-belt treadmill. A segmental power analysis quantified muscle contributions to vertical body segment mechanical power, which were integrated over the stance phase of running (Run) and the hop (Skip 1) and step (Skip 2) of skipping to calculate mechanical work. Higher vertical work was done by the gluteus maximus, vasti, and soleus in Skip 1, primarily through power generation to the trunk, compared to power absorption in Run and Skip 2. Thus, despite lower muscle force impulses in Skip 1, muscles generate power through concentric contractions, leading to greater metabolic cost than in running. These muscle force impulses contribute to propelling the COM upward in Skip 1 (rather than decelerating downward COM motion in Run and Skip 2), which raises the COM and contributes to the greater COM displacement in skipping compared to running., 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 © 2025 Elsevier Ltd. All rights reserved.)

Objective: The study objective was to determine whether the clinical response of older adults with knee osteoarthritis and overweight or obesity to 18 months of diet and exercise (D + E) or attention control (C) interventions differed between participants from rural versus urban communities., Methods: Participants were 823 older adults (mean age, 64.6 years; 77% women) with knee osteoarthritis and overweight or obesity who resided in rural (n = 410) and urban (n = 413) counties in North Carolina. All were enrolled in the Weight Loss and Exercise for Communities with Arthritis in North Carolina clinical trial that randomly assigned participants to either 18 months of D + E or C interventions. General linear models were used to examine differences in clinical outcomes between rural and urban groups after adjusting for covariates., Results: The rural group had significant differences (P < 0.05) at baseline in clinical outcomes, education, comorbidities, medication use, and income compared with the urban dwellers. After adjusting for baseline differences, the group (rural or urban) by treatment (D + E or C) interactions for Western Ontario McMasters Universities Osteoarthritis Index (WOMAC) pain (rural: D + E - C = -0.63, 95% confidence interval [CI] -1.31 to 0.06; urban: D + E - C= -0.29, 95% CI -0.99 to 0.41; P = 0.50) and WOMAC function (rural: D + E - C = -4.60, 95% CI -6.89 to -2.31; urban: D + E - C = -1.38, 95% CI -3.73 to 0.94; P = 0.054) indicated that the groups responded similarly to the interventions., Conclusion: Among participants with knee osteoarthritis and overweight or obesity, D + E compared to C led to similar pain outcomes in rural and urban dwellers that favored D + E. The possibility that there may be greater differential efficacy in functional outcomes among rural participants needs further study., (© 2024 The Author(s). Arthritis Care & Research published by Wiley Periodicals LLC on behalf of American College of Rheumatology.)

Objective: Obesity exacerbates pain and functional limitation in persons with knee osteoarthritis (OA). In the Weight Loss and Exercise for Communities with Arthritis in North Carolina (WE-CAN) study, a community-based diet and exercise (D + E) intervention led to an additional 6 kg weight loss and 20% greater pain relief in persons with knee OA and body mass index (BMI) >27 kg/m 2 relative to a group-based health education (HE) intervention. We sought to determine the incremental cost-effectiveness of the usual care (UC), UC + HE, and UC + (D + E) programs, comparing each strategy with the "next-best" strategy ranked by increasing lifetime cost., Methods: We used the Osteoarthritis Policy Model to project long-term clinical and economic benefits of the WE-CAN interventions. We considered three strategies: UC, UC + HE, and UC + (D + E). We derived cohort characteristics, weight, and pain reduction from the WE-CAN trial. Our outcomes included quality-adjusted life years (QALYs), cost, and incremental cost-effectiveness ratios (ICERs)., Results: In a cohort with mean age 65 years, BMI 37 kg/m 2 , and Western Ontario and McMaster Universities Osteoarthritis Index pain score 38 (scale 0-100, 100 = worst), UC leads to 9.36 QALYs/person, compared with 9.44 QALYs for UC + HE and 9.49 QALYS for UC + (D + E). The corresponding lifetime costs are $147,102, $148,139, and $151,478. From the societal perspective, UC + HE leads to an ICER of $12,700/QALY; adding D + E to UC leads to an ICER of $61,700/QALY., Conclusion: The community-based D + E program for persons with knee OA and BMI >27kg/m 2 could be cost-effective for willingness-to-pay thresholds greater than $62,000/QALY. These findings suggest that incorporation of community-based D + E programs into OA care may be beneficial for public health., (© 2024 American College of Rheumatology.)

Objective: The purpose of this study was to determine whether clinical, health-related quality of life (HRQL), and gait characteristics in adults with knee osteoarthritis (OA) differed by obesity category., Methods: This cross-sectional analysis of 823 older adults (mean age 64.6 years, SD 7.8 years) with knee OA and overweight or obesity compared clinical, HRQL, and gait outcomes among obesity classifications (overweight or class I, body mass index [BMI] 27.0-34.9; class II, BMI 35.0-39.9; class III BMI ≥40.0)., Results: Patients with class III obesity had worse Western Ontario McMasters Universities Arthritis Index knee pain (0-20) than the overweight or class I (mean 8.6 vs 7.0; difference 1.5; 95% confidence interval [CI] 1.0-2.1; P < 0.0001) and class II (mean 8.6 vs 7.4; difference 1.1; 95% CI 0.6-1.7; P = 0.0002) obesity groups. The Short Form 36 physical HRQL measure was lower in the class III obesity group compared to the overweight or class I (mean 31.0 vs 37.3; difference -6.2; 95% CI -7.8 to -4.7; P < 0.0001) and class II (mean 31.0 vs 35.0; difference -3.9; 95% CI -5.6 to -2.2; P < 0.0001) obesity groups. The class III obesity group had a base of support (cm) during gait that was wider than that for the overweight or class I (mean 14.0 vs 11.6; difference 3.3; 95% CI 2.6-4.0; P < 0.0001) and class II (mean 14.0 vs 11.6; difference 2.4; 95% CI 1.6-3.2; P < 0.0001) obesity groups., Conclusion: Among adults with knee OA, those with class III obesity had significantly higher pain levels and worse physical HRQL and gait characteristics compared to adults with overweight or class I or class II obesity., (© 2023 The Authors. Arthritis Care & Research published by Wiley Periodicals LLC on behalf of American College of Rheumatology.)

The increased running participation in women and men over 40 years has contributed to scientific interest on the age-related and gender differences in running performance and biomechanics over the last decade. Gender differences in running biomechanics have been studied extensively in young runners, with inconsistent results. Understanding how gender influences the age-related differences in running mechanics could help develop population-specific training interventions or footwear to address any potential different mechanical demands. The purpose of this study was to assess gender and age effects on lower limb joint mechanics while running. Middle-aged men (57 ± 5 years) and women (57 ± 8 years) and young men (28 ± 6 years) and women (30 ± 6 years) completed five overground running trials at a set speed of 2.7 m/s while lower limb kinematics and ground reaction forces were collected. Lower limb joint kinetics were computed, normalized to body mass and compared between age and gender groups using two-factor analyses of variance. Women reported slower average running paces than men and middle-aged runners reported slower running paces than young runners. We confirmed that young runners run with more ankle, but less hip positive work and peak positive power compared to middle-aged runners (i.e., age-related distal-to-proximal shift in joint kinetics). We also present a novel finding that women run with more ankle, but less hip peak positive power compared to men suggesting an ankle dominant strategy in women at a preferred and comfortable running pace. However, the age-related distal-to-proximal shift in joint kinetics was not different between genders., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Osteoarthritis (OA), the leading cause of disability among adults, has no cure and is associated with significant comorbidities. The premise of this randomized clinical trial is that, in a population at risk, a 48-month program of dietary weight loss and exercise will result in less incident structural knee OA compared to control., Methods/design: The Osteoarthritis Prevention Study (TOPS) is a Phase III, assessor-blinded, 48-month, parallel 2 arm, multicenter randomized clinical trial designed to reduce the incidence of structural knee OA. The study objective is to assess the effects of a dietary weight loss, exercise, and weight-loss maintenance program in preventing the development of structural knee OA in females at risk for the disease. TOPS will recruit 1230 ambulatory, community dwelling females with obesity (Body Mass Index (BMI) ​≥ ​30 ​kg/m 2 ) and aged ≥50 years with no radiographic (Kellgren-Lawrence grade ≤1) and no magnetic resonance imaging (MRI) evidence of OA in the eligible knee, with no or infrequent knee pain. Incident structural knee OA (defined as tibiofemoral and/or patellofemoral OA on MRI) assessed at 48-months from intervention initiation using the MRI Osteoarthritis Knee Score (MOAKS) is the primary outcome. Secondary outcomes include knee pain, 6-min walk distance, health-related quality of life, knee joint loading during gait, inflammatory biomarkers, and self-efficacy. Cost effectiveness and budgetary impact analyses will determine the value and affordability of this intervention., Discussion: This study will assess the efficacy and cost effectiveness of a dietary weight loss, exercise, and weight-loss maintenance program designed to reduce incident knee OA., Trial Registration: ClinicalTrials.gov Identifier: NCT05946044., Competing Interests: Dr. Katz and Dr. Losina received research grant funding from Samumed and Flexion Therapeutics. Elena Losina has also received research funding from Pfizer. Dr. Hunter received research funding from Pfizer, Novartis, Lilly, Merck Serono, TLC Biopharmaceuticals and Kolon. Dr. Guermazi is a consultant for Pfizer, Novartis, TissueGene, Coval, Medipost, ICM and TrialSpark, and is a shareholder in Boston Imaging Core Lab. Kurt Spindler is a consultant for the National Football League and Novopedics, Inc. Dr.Cook receives research support from AO Trauma, Arthrex, Inc., Collagen Matrix Inc., DePuy, A Johnson & Johnson Company, Musculoskeletal Transplant Foundation, Orthopaedic Trauma Association, Purina, Regenosine, SITES Medical, Thieme, and Trupanion., (© 2023 The Author(s).)

Chronic exposure to high tibiofemoral joint (TFJ) contact forces can be detrimental to knee joint health. Load carriage increases TFJ contact forces, but it is unclear whether medial and lateral tibiofemoral compartments respond similarly to incremental load carriage. The purpose of our study was to compare TFJ contact forces when walking with 15% and 30% added body weight. Young healthy adults (n = 24) walked for 5 minutes with no load, 15% load, and 30% load on an instrumented treadmill. Total, medial, and lateral TFJ contact peak forces and impulses were calculated via an inverse dynamics informed musculoskeletal model. Results of 1-way repeated measures analyses of variance (α = .05) demonstrated total, medial, and lateral TFJ first peak contact forces and impulses increased significantly with increasing load. Orthogonal polynomial trends demonstrated that the 30% loading condition led to a curvilinear increase in total and lateral TFJ impulses, whereas medial first peak TFJ contact forces and impulses responded linearly to increasing load. The total and lateral compartment impulse increased disproportionally with load carriage, while the medial did not. The medial and lateral compartments responded differently to increasing load during walking, warranting further investigation because it may relate to risk of osteoarthritis.

Skipping has been proposed as a viable cross-training exercise to running due to its lower knee contact forces and higher whole-body energy expenditure. However, how individual muscle forces, energy expenditure, and joint loading are affected by differences in running and skipping mechanics remains unclear. The purpose of this study was to compare individual muscle forces, energy expenditure, and lower extremity joint contact forces between running and skipping using musculoskeletal modeling and simulations of young adults (n = 5) performing running and skipping at 2.5 m·s-1 on an instrumented treadmill. In agreement with previous work, running had greater knee and patella contact forces than skipping which was accompanied by greater knee extensor energetic demand. Conversely, skipping had greater ankle contact forces and required greater energetic demand from the uniarticular ankle plantarflexors. There were no differences in hip contact forces between gaits. These findings further support skipping as a viable alternative to running if the primary goal is to reduce joint loading at the commonly injured patellofemoral joint. However, for those with ankle injuries, skipping may not be a viable alternative due to the increased ankle loads. These findings may help clinicians prescribe activities most appropriate for a patient's individual training or rehabilitation goals.

This study aimed to examine the feasibility of using time-to-contact measures during the perturbation protocol in people with diabetes mellitus. Three-dimension motion capture and force data were collected during 0.5-s perturbations in four directions (forward, backward, right, and left) and at two accelerations (20 and 40 cm/s2) to compute the time-to-contact. Time-to-contact analysis was divided into three phases: perturbation, initial recovery, and final recovery. The statistical analysis showed the main effects of Direction and Phase (p < .01) as well as a Direction by Phase interaction (p < .01). Backward perturbation with lower acceleration and backward/forward perturbation with higher acceleration had deleterious effects on postural stability in people with diabetes mellitus.

Objective: To determine whether long-term diet (D) and exercise (E) interventions, alone or in combination (D+E), have beneficial effects for older adults with knee osteoarthritis (OA) 3.5 years after the interventions end., Methods: This is a secondary analysis of a subset (n = 94) of the first 184 participants who had successfully completed the Intensive Diet and Exercise in Arthritis (IDEA) trial (n = 399) and who consented to follow-up testing. Participants were older (age ≥55 years), overweight, and obese adults with radiographic and symptomatic knee OA in at least 1 knee who completed 1.5-year D+E (n = 27), D (n = 35), or E (n = 32) interventions and returned for 5-year follow-up testing an average of 3.5 years later., Results: During the 3.5-years following the interventions, weight regain in D+E and D was 5.9 kg (7%) and 3.1 kg (4%), respectively, with a 1-kg (1%) weight loss in E. Compared to baseline, weight (D+E -3.7 kg [P = 0.0007], D -5.8 kg [P < 0.0001], E -2.9 kg [P = 0.003]) and Western Ontario and McMaster Universities Osteoarthritis Index pain subscale scores (D+E -1.2 [P = 0.03], D -1.5 [P = 0.001], E -1.6 [P = 0.0008]) were lower in each group at the 5-year follow-up. The effect of group assignment at the 5-year follow-up was significant for body weight, with D being less than E (-3.5 kg; P = 0.04)., Conclusion: Older adults with knee OA who completed 1.5-year D or D+E interventions experienced partial weight regain 3.5 years later; yet, relative to baseline, they preserved statistically significant changes in weight loss and reductions in knee pain., (© 2021 American College of Rheumatology.)

Aging is associated with a distal-to-proximal shift in joint kinetics during walking. This plasticity of gait is amplified rather than attenuated in old adults with high physical capacity. Because running is associated with greater kinetic demands at the ankle, older individuals with more versus less lifetime running exposure may retain a larger proportion of their ankle kinetics. The purpose of the study was to compare lower-extremity joint kinetics during walking between middle-aged runners with high and low lifetime running exposure. Eighteen middle-aged runners (9 per group) participated. Joint kinetics were calculated from kinematic and ground reaction force data during overground walking at 1.3 m·s-1 and compared between groups. High exposure runners produced 50% greater positive hip work (P = .03; Cohen d = 1.02) during walking compared with low exposure runners, but ankle kinetics were not different between groups. No other differences in joint kinetics or kinematics were observed between groups. These findings suggest that the age-related increase in hip joint kinetics during walking could be a compensatory gait strategy that is not attenuated by lifetime running exposure alone. Finally, the amount of lifetime running exposure did not affect ankle kinetics during walking in middle-aged runners.

Background: The health benefits of running based exercise programs are plentiful however the high rate of injury in these programs often reduces or eliminates exercise participation. Skipping has shorter steps, reduced vertical ground reaction forces (GRFs), and lower knee extensor torques, compared to running forming the basis of the present hypothesis that skipping would have lower tibio-femoral and patello-femoral joint contact forces., Research Question: The purpose of this study was to compare knee contact forces between skipping and running at the same speed. We also compared metabolic cost of these two gaits to examine the idea that the larger vertical displacement in skipping is a primary factor in its previously reported high metabolic cost., Methods: The study evaluated joint contact forces through musculoskeletal modeling with GRF and 3D kinematic data and metabolic cost using oxygen consumption data from 20 young, healthy, trained participants as they skipped and ran on an instrumented treadmill at 2.68 m/s., Results: Skipping, compared to running, had substantially lower tibio-femoral and patello-femoral joint contact forces and linear impulses on both per-step and per-kilometer (i.e. lower cumulative loads) bases and also 30% higher metabolic cost. The lower joint loads in skipping were directly associated with its shorter steps and the higher metabolic cost was directly associated to its larger vertical displacement through the stride., Significance: As joint loads may predispose individuals to running related injuries, skipping presents an attractive alternative exercise modality with additional increased aerobic benefits., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Objective: To assess the effect of quadriceps strengthening on quadriceps muscle force, power, and work and tibio-femoral compressive loads during walking in adults with knee osteoarthritis., Methods: Study design: Two-center, randomized, controlled trial., Intervention: Patients with knee osteoarthritis were randomly allocated to quadriceps strengthening program (3 times weekly) or no attention control group., Main Outcome Measures: Primary outcome was change from baseline in peak quadriceps force during walking at 12 weeks. Secondary outcomes included quadriceps power and work, knee compression forces during walking estimated with musculoskeletal modeling, muscle strength and pain and function. Outcomes were measured at baseline and 12 weeks., Results: 30 patients were randomized to receive either training (n = 15) or no attention (n = 15). At follow-up, there were no statistical differences between groups for maximum quadriceps force, quadriceps positive power, negative work, and positive work, and knee compressive force. Maximum negative quadriceps power in early stance was statistically significantly increased 36% in the training group compared to the control group which was most likely partially a response to faster walking velocity at follow-up. Muscle strength and patient reported pain and function were improved in the training group compared to the control group., Conclusions: Quadriceps strength training leads to increased muscle strength and improved symptomatic and functional outcomes but does not change quadriceps or knee joint biomechanics during walking. The biomechanical mechanism of improved health with strength training in knee osteoarthritis patients remains unknown. ClinicalTrials.gov Identifier: NCT01538407., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

National Biomechanics Day (NBD) seeks to expand the influence and impact of Biomechanics on our society by expanding the awareness of Biomechanics among young people. NBD will manifest this goal through worldwide, synchronized and coordinated celebrations and demonstrations of all things Biomechanics with high school students. NBD invites all Biomechanists to participate in NBD 2018, http://nationalbiomechanicsday.asbweb.org/., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Running speed is slower in middle-age compared with younger runners due to reduced ankle but not hip and knee kinetic output. Running-specific training helps attenuate age-related declines in measures of endurance, muscle strength, and gait speed. Considering the adaptability of the human body in response to imposed stresses, maintaining training volume and intensity may play a role in modifying running biomechanics in middle-age runners., Purpose: To compare running biomechanics between young and middle-age runners when controlling for the confounding effects of training volume and intensity., Methods: Fifteen middle-age runners, 15 young runners with similar training volume as the middle-age group and, 15 young runners with similar preferred training paces (i.e., intensity) as the middle-age runners participated in the study. Lower-limb joint kinetics were calculated from kinematic and ground reaction force data during overground running at a submaximal speed and compared among groups., Results: Middle-age runners ran with similar peak ankle power compared with volume-matched younger runners although peak plantarflexor moment was 10.5% lower in the middle age group (P = 0.046; Cohen d = 0.78). Middle-age runners ran with similar ankle plantarflexor moment and joint power compared with training pace-matched young runners. As expected, no age-related differences were observed in hip and knee kinetics when training volume or pace were matched between age groups. These results suggest that training pace may be more effective in attenuating age-related declines in plantarflexor kinetics in middle-age runners., Conclusions: From these findings, we propose the hypothesis that both training volume and training pace may play a role in maintaining plantarflexor kinetics but that training pace may have a greater impact on ankle plantarflexor kinetics in middle-age runners.

A consensus exists that high knee joint forces are a precursor to knee osteoarthritis and weight loss reduces these forces. Because large weight loss also leads to increased step length and walking velocity, knee contact forces may be reduced less than predicted by the magnitude of weight loss. The purpose was to determine the effects of weight loss on knee muscle and joint loads during walking in Class III obese adults. We determined through motion capture, force platform measures and biomechanical modeling the effects of weight loss produced by gastric bypass surgery over one year on knee muscle and joint loads during walking at a standard, controlled velocity and at self-selected walking velocities. Weight loss equaling 412 N or 34% of initial body weight reduced maximum knee compressive force by 824 N or 67% of initial body weight when walking at the controlled velocity. These changes represent a 2:1 reduction in knee force relative to weight loss when walking velocity is constrained to the baseline value. However, behavioral adaptations including increased stride length and walking velocity in the self-selected velocity condition attenuated this effect by ∼50% leading to a 392 N or 32% initial body weight reduction in compressive force in the knee joint. Thus, unconstrained walking elicited approximately 1:1 ratio of reduction in knee force relative to weight loss and is more indicative of walking behavior than the standard velocity condition. In conclusion, massive weight loss produces dramatic reductions in knee forces during walking but when patients stride out and walk faster, these favorable reductions become substantially attenuated., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Unlabelled: Running has high injury rates, especially among older runners. Most aging literature compares young with old runners without accounting for the progression of biomechanics throughout the lifespan. We used age as a continuous variable to investigate the continuum of age-related gait adaptations in running along with determining the chronology and rate of these adaptations., Purpose: This study aimed to identify the relations among age and selected running biomechanics throughout the range of 18-60 yr., Methods: Experienced (n = 110) healthy runners (male, 54%) provided informed consent and ran at their training pace while motion and force data were captured. Kinematics, ground reaction forces (GRF), and lower limb joint torques and powers were correlated with age using Pearson product-moment correlations and linear regression., Results: Running velocity was inversely related to age (r = -0.27, P = 0.005) because of decreased stride length (r = -0.25, P = 0.008) but not rate. Peak vertical GRF (r = -0.23, P = 0.016) and peak horizontal propulsive GRF decreased with age (r = -0.38, P < 0.0001). Peak ankle torque (r = -0.32, P = 0.0007) and peak negative (r = 0.34, P = 0.0003) and positive (r = -0.37, P < 0.0001) ankle power decreased with age. Age-based regression equations and per-year reductions in all variables significantly related to age are reported., Conclusions: Data support previous work showing lower GRF, stride length, and velocity in old runners. Results are novel in showing the rate of decline in running biomechanics on a per-year basis and that mechanical reductions at the ankle but not at the hip or knee were correlated with age, confirming a previous observation of biomechanical plasticity with age showing reduced ankle but not hip function in gait.

The purpose of this study was to develop a statistical model to describe the electromyography (EMG) signal frequency changes during a submaximal isometric contraction. Thirty subjects performed a 30-second isometric contraction of the biceps brachii muscle at 80% of the maximal voluntary isometric force. Surface EMG electrodes recorded electrical activity of the biceps brachii. Zero-Crossing-Rate was calculated to identify EMG frequency shifts. The mean frequencies for every one-second period were used to calculate a linear relationship between frequency and time. A significant relationship (p<0.05) between slope and initial frequency value was identified. The model described EMG frequency changes during submaximal effort of biceps brachii up to 15 seconds. The prediction error was 9.8%. Modifying this equation to initial values of frequency of each participant decreased prediction error to 7.2%. These results demonstrate that despite individual differences between subjects it is possible to derive single equation that describes EMG alterations during submaximal, isometric contractions across a homogeneous group of people.

This study tested the hypothesis that skeletal muscles generate more mechanical energy in gait tasks that raise the center of mass compared to the mechanical energy they dissipate in gait tasks that lower the center of mass despite equivalent changes in total mechanical energy. Thirteen adults ran on a 10 degrees decline and incline surface at a constant average velocity. Three-dimensional (3D) joint powers were calculated from ground force and 3D kinematic data using inverse dynamics. Joint work was calculated from the power curves and assumed to be due to skeletal muscle-tendon actuators. External work was calculated from the kinematics of the pelvis through the gait cycle. Incline vs. decline running was characterized with smaller ground forces that operated over longer lever arms causing larger joint torques and work from these torques. Total lower extremity joint work was 28% greater in incline vs. decline running (1.32 vs. -1.03J/kgm, p<0.001). Total lower extremity joint work comprised 86% and 71% of the total external work in incline (1.53J/kgm) and decline running (-1.45J/kgm), which themselves were not significantly different (p<0.180). We conjectured that the larger ground forces in decline vs. incline running caused larger accelerations of all body tissues and initiated a greater energy-dissipating response in these tissues compared to their response in incline running. The runners actively lowered themselves less during decline stance and descended farther as projectiles than they lifted themselves during incline stance and ascended as projectiles. These data indicated that despite larger ground forces in decline running, the reduced displacement during downhill stance phases limited the work done by muscle contraction in decline compared to incline running.

This study examined the neuromuscular adaptations of young and old adults in response to a challenge to balance during gait. 12 young (22.2 +/- 2.0 yr.) and 10 old adults (78.8 +/- 6.3 yr.) performed five level walking trials with and without a challenge to balance which consisted of adding a load bilaterally to the participants' ankles and increasing gait speed (1.5 m/sec. and 1.7 m/sec.). Onset, duration, and amplitude of muscle activity in the vastus lateralis, rectus femoris, biceps femoris, and semimembranosus were calculated. Old adults responded to the added load by increasing the activation intensity of their vastus lateralis and semimembranosus disproportionately when compared with young adults. Also, old adults activated their knee flexors earlier and all muscles for a longer period of time than young adults. These findings suggest old adults alter both magnitude of activation and duration of lower extremity musculature in response to increased inertial and velocity demands, and these response characteristics differ from those of young adults.