Bone health and physical activity in adolescents with juvenile idiopathic arthritis: a cross-sectional case-control study.

BACKGROUND: Adolescents with juvenile idiopathic arthritis (JIA) tend to engage in less physical activity than their typically developing peers. Physical activity is essential for bone development and reduced physical activity may detrimentally effect bone health. Thus, we examined differences in total body bone mineral content (BMC) and areal bone mineral density (aBMD) between adolescents with JIA and adolescent controls without JIA. We also examined associations between moderate-to-vigorous physical activity (MVPA), lean mass, and bone outcomes. METHODS: Participants included 21 adolescents with JIA (14 females, 7 males) and 21 sex- and age-matched controls aged 10-20 years. Assessments included: height; weight; triple-single-leg-hop distance (TSLH); MVPA by accelerometry; and total body BMC, aBMD, and lean mass measured using dual X-ray absorptiometry. Height-adjusted z-scores were calculated for BMC and aBMD and used for all analyses. Multiple linear mixed effects models examined group differences in BMC and aBMD, adjusting for sex, maturity, MVPA, TSLH, and lean mass. Participants clusters, based on sex and age (within 18 months), were considered random effects. RESULTS: Adolescents with JIA had lower total body aBMD z-scores [ß (95% CI); -0.58 (-1.10 to -0.07), p = 0.03] and BMC z-scores [-0.47 (-0.91 to -0.03), p = 0.04] compared with controls. Mean daily MVPA was 22.0 min/day lower in adolescents with JIA than controls; however, MVPA was not associated with aBMD [-0.01 (-0.01 to 0.01), p = 0.32] or BMC [0.00 (-0.01 to 0.00), p = 0.39]. Lean mass was positively associated with aBMD [0.05 (0.01 to 0.09) g/cm2, p = 0.03] and BMC [0.06 (0.03 to 0.10) g, p < 0.001]. CONCLUSION: Adolescents with JIA had lower total body aBMD and BMC compared with sex- and age-matched controls without JIA. Group differences in bone outcomes were not associated with the lower MVPA participation of adolescents with JIA. Despite this, physical activity should still be encouraged as it promotes physical well-being.

Physical Activity Levels and Adiposity in Ambulant Children and Adolescents With Cerebral Palsy Compared With Their Typically Developing Peers.

PURPOSE: This study assessed physical activity (PA) and body composition of ambulatory children and adolescents with cerebral palsy (CP) and their typically developing peers. METHODS: Participants included youth with CP (ages 8-18 y and Gross Motor Function Classification System [GMFCS] levels I-III) and their typically developing peers. Outcomes included PA (actigraphy) and fat/lean mass index (FMI/LMI; dual-energy X-ray absorptiometry). Statistical analyses included linear mixed effects models with Bonferroni adjustment. Fixed effects were study group (CP and typically developing); random effects were participant clusters (sex and age). Exploratory analyses included association of body composition and PA, GMFCS level, and CP involvement (unilateral and bilateral). RESULTS: Seventy-eight participants (CP: n = 40, girls: n = 29; GMFCS I: n = 20; GMFCS II: n = 14; GMFCS III: n = 6) met inclusion criteria. Individuals with CP had lower moderate to vigorous PA (MVPA; ß = -12.5; 98.3% confidence interval, -22.6 to -2.5 min; P = .004) and lower LMI (ß = -1.1; 97.5% confidence interval, -2.1 to -0.0 kg/m2; P = .020). Exploratory analyses indicated increased LMI with greater MVPA (P = .001), reduced MVPA for GMFCS II (P = .005) and III (P = .001), increased sedentary time for GMFCS III (P = .006), and greater fat mass index with unilateral motor impairment (P = .026). CONCLUSIONS: The findings contribute to the knowledge base of increasing MVPA and LMI deficits with the greater functional impact of CP. Associations of increasing LMI with greater MVPA support efforts targeting enhanced PA participation to promote independent mobility.

Secondary consequences of juvenile idiopathic arthritis in children and adolescents with knee involvement: physical activity, adiposity, fitness, and functional performance.

OBJECTIVE: Secondary consequences of juvenile idiopathic arthritis (JIA) may impact long-term health outcomes. This study examined differences in physical activity, cardiorespiratory fitness, adiposity, and functional performance in children and adolescents with JIA compared to their typically developing (TD) peers. METHODS: Participants with JIA (n = 32; 10-20 years old) and their TD peers (n = 35) volunteered for assessments of: daily moderate-to-vigorous physical activity (MVPA, body-worn accelerometer); peak oxygen consumption (VO2 Peak, incremental bike test); fat mass index (FMI, dual-energy X-ray absorptiometry); and triple-single-leg-hop (TSLH) distance. Statistical analyses were performed in R using four linear mixed-effect models with Bonferroni adjustment (⍺ = 0.0125). Fixed effects were group, sex, and age. Participant clusters based on sex and age (within 1.5 years) were considered as random effects. RESULTS: Participants with JIA displayed lower mean daily MVPA than their TD peers [p = 0.006; ß (98.75% CI); -21.2 (-40.4 to -2.9) min]. VO2 Peak [p = 0.019; -1.4 (-2.5 to -0.2) ml/kg/min] decreased with age. Females tended to have lower VO2 Peak [p = 0.045; -6.4 (-13.0 to 0.4) ml/kg/min] and greater adiposity [p = 0.071; 1.4 (-0.1 to 3.0) kg/m2] than males. CONCLUSION: The findings support the need for strategies to promote MVPA participation in children and adolescents with JIA. Sex and age should be considered in research on the consequences of JIA.

More Than Just Adolescence: Differences in Fatigue Between Youth With Cerebral Palsy and Typically Developing Peers.

OBJECTIVE: To quantify differences in fatigue and disordered sleep between adolescents with cerebral palsy (CP) and their typically developing peers. A secondary aim was to investigate the association between fatigue and disordered sleep in adolescents with CP. METHODS: A convenience sample of 36 youth with CP aged 10-18 years was matched for age and sex with 36 typically developing peers. The Fatigue Impact and Severity Self-Assessment (FISSA), the Patient-Reported Outcome Measurement Information System (PROMIS) fatigue profile, and the Sleep Disturbance Scale for Children (SDSC) were collected. RESULTS: Higher fatigue was reported in participants with CP than in their typically developing peers based on the FISSA total score (mean paired difference=19.06; 99% confidence interval [CI], 6.06-32.1), the FISSA impact subscale (mean paired difference=11.19; 99% CI, 3.96-18.4), and the FISSA Management and Activity Modification subscale (mean paired difference=7.86; 99% CI, 1.1-14.6). There were no differences between groups in the PROMIS fatigue profile (mean paired difference=1.63; 99% CI, -1.57-4.83) or the SDSC total score (mean paired difference=2.71; 99% CI, -2.93-8.35). CONCLUSION: Youth with CP experienced significantly more fatigue than their peers as assessed by a comprehensive measure that considered both general and diagnosis-specific concerns. Sleep did not differ between youth with CP and their typically developing peers. These findings underscore the need to consider the clinical management of fatigue across the lifespan of individuals with CP to prevent the associated deterioration of functional abilities.

Associations of inter-segmental coordination and treadmill walking economy in youth with cerebral palsy.

This study investigated associations of thigh-shank coordination deficit severity and metabolic demands of walking in youth with cerebral palsy (CP) and their typically developing (TD) peers. Youth (ages 8-18 years) with hemiplegic and diplegic CP [Gross Motor Classification System (GMFCS) I-III] and their age (within 12 months) and sex-matched peers performed a modified six-minute-walk-test on a treadmill. Kinematics (Motion Analysis, USA, 240 Hz) and mass-specific gross metabolic rate (GMR; COSMED, Italy) were analyzed for minute two of treadmill walking. Thigh-shank coordination was determined using continuous relative phase (CRP) analysis. GMR was normalized using participant specific Froude numbers (i.e. GMREq). Maximum and minimum CRP deficit angles (CRPMax,CRPMin) were analysed in SPSS (IBM, USA) using paired samples t-tests with Bonferroni correction (p = 0.0125). Associations of knee extension angle deficit (KEDMax) and coordination outcomes with GMREq (log) were assessed using multiple linear regression. Twenty-eight matched pairs were included, demonstrating significantly larger CRPMax for youth with CP [GMFCS I mean pair difference (98.75%CI) 8.2 (-0.1,16.5), P = 0.013; GMFCS II/III 26.1 (2.3,50.0), P = 0.008]. Joint kinematics and coordination outcomes were significantly associated with GMREq (P < 0.001), primarily due to CRPMax (P < 0.001), leading to a 1.7 (95%CI; 1.1, 2.4)% increase in GMREq for every degree increase in CRPMax. These findings indicate an association of thigh-shank coordination deficit severity and increasing metabolic demands of walking in youth with CP. CRP may be a clinically useful predictor of metabolic demands of walking in CP. Future work will evaluate the sensitivity of CRP to coordination and walking economy changes with surgical and non-surgical management.

Consequences of Juvenile Idiopathic Arthritis on Single Leg Squat Performance in Youth.

OBJECTIVE: Juvenile idiopathic arthritis (JIA) affects body structure and function outcomes that may increase the risk of acute joint injury. The purpose of this study was to examine single leg squat (SLS) biomechanics for youth with JIA and their healthy peers. The study design was a matched pair cohort study. METHODS: Sixty-five youth (JIA n = 30; control n = 35) participated in this ethics-approved study. Participants performed 3 sets of 5 consecutive SLS tasks. Disease activity and functional status were assessed using the Juvenile Arthritis Disease Activity Score and Child Health Assessment Questionnaire. Indexed (most-affected leg [JIA]; dominant leg [control]) and contralateral extremity biomechanics were obtained using a 12-camera system. Outcomes included hip flexion/extension (FE), adduction/abduction (AA), and internal/external (IE) rotation range of motion (ROM). Data were analyzed using a multivariate random coefficient model in R (α⍺ = 0.05). RESULTS: A total of 29 matched pairs were analyzed. Youth with JIA had low disease activity and performed the SLS with a more internally rotated hip (indexed leg P = 0.023, ß = -1.9°). Female participants displayed greater hip FE (indexed leg P = 0.015, ß = -4.3°; contralateral leg P = 0.005, ß = -4.8°) and IE ROM (indexed leg P = 0.021, ß = -2.1°) than male participants. Associations were observed for body mass index and hip IE ROM (contralateral leg P = 0.001, ß = -0.4°), knee flexion angle, and hip FE ROM (indexed leg P = 0.001, ß = 0.4°; contralateral leg P = 0.001, ß = 0.5°) and AA (indexed leg P = 0.010, ß = 0.1°; contralateral leg P = 0.002, ß = 0.2°). CONCLUSION: This study identified functional alterations for an SLS in youth with JIA. These findings support the use of physical therapy as part of a multidisciplinary management approach, to restore normal hip posture and movement.

Vertical Drop Jump Performance in Youth With Juvenile Idiopathic Arthritis.

OBJECTIVE: Juvenile idiopathic arthritis (JIA) is associated with altered body structure and function outcomes that may expose youth with JIA to a greater risk of secondary joint injury. This study aimed to examine differences in vertical drop jump (VDJ) biomechanics for youth with JIA and healthy youth (control group). METHODS: The present study was a matched pair cohort study. Youth with JIA (n = 30) and their age- and sex-matched control peers participated in this ethics-approved study. Lower-extremity biomechanics information was obtained using a motion analysis system (Motion Analysis) and 2 force plates (AMTI). Biomechanics outcomes included hip, knee, and ankle joint angles, ground reaction forces (GRF), and VDJ phase durations. Other outcomes included disease activity, physical disability, and sports participation. Matched pairs data (JIA-control) were analyzed using a multivariate random coefficient model (version 3.5.0, R Core Team; joint angles, potential confounders) and paired samples t-tests with Bonferroni correction (α = 0.0125; GRF, VDJ phase durations). RESULTS: Youth with JIA had low disease activity, pain, and disability scores. Youth with JIA maintained a more erect posture at the hip (ß = -4.0°, P = 0.004), knee (ß = 7.5°, P = 0.004) and ankle (ß = -2.6°, P = 0.001). GRF and phase durations outcomes did not meet criteria for significant differences. Knee extension increased with participant age (ß = -1.0°, P = 0.002), while female participants displayed greater hip flexion (ß = -6.6°, P = 0.001) and less ankle dorsiflexion (ß = 2.3°, P = 0.006). CONCLUSION: This study provides evidence for a stiff knee landing strategy by youth with JIA. These findings inform targets for physical therapy management to mitigate the risks of a secondary joint injury in sports participation.

Gait Adaptations in Youth With Juvenile Idiopathic Arthritis.

OBJECTIVE: Juvenile idiopathic arthritis (JIA) affects body structure and function and physical activity outcomes. The present study was undertaken to examine differences in gait kinematics during fixed-speed treadmill walking for youth with JIA and typically developing (TD) youth. METHODS: Sagittal plane gait kinematics were obtained using a 12-camera system (Motion Analysis) for youth with JIA (n = 30) and their age and sex-matched TD peers (n = 30). Outcomes included disease activity, pain, well-being, and peak sagittal hip, knee, and ankle joint angles. Kinematics were analyzed for the indexed leg (IL) (i.e., the affected leg of participants with JIA) compared to the dominant leg of TD participants and for the contralateral leg (CL) (i.e., the less/not affected leg of participants with JIA) compared to the nondominant leg of TD participants. Kinematics differences were investigated using multivariate Hotelling's T2 statistic (paired samples; α = 0.05) and simultaneous 95% confidence intervals (95% CIs). Potential confounders (age, sex, body mass index) were assessed using linear mixed-effects models with random effect for pairs. RESULTS: Youth with JIA had low disease activity, pain, and disability scores. Deviations in bilateral joint angles were observed (IL P = 0.015, CL P = 0.009). Youth with JIA walked with greater initial hip flexion (mean difference IL 2.8° [95% CI -0.6, 6.2]; CL 3.0° [-0.9, 6.9]) and lower knee extension (mean difference IL -2.2° [95% CI -4.4, 0.1]; CL -3.3° [-7.4, 0.8]), and lower hip extension during terminal stance (mean difference IL 3.4° [95% CI -0.3, 7.0]; CL 4.0° [1.0, 7.0]). CONCLUSION: Despite low disease activity, youth with JIA avoided the close-packed knee position, commonly associated with joint inflammation and pain. These findings highlight secondary consequences of JIA and inform targets for physical therapy management for youth with JIA.

Exercise Therapy in Juvenile Idiopathic Arthritis: A Systematic Review and Meta-Analysis.

OBJECTIVE: To conduct a systematic review to evaluate the efficacy of exercise interventions in improving outcomes across domains of functioning and disability in children and adolescents with juvenile idiopathic arthritis (JIA). DATA SOURCES: Seven electronic databases were systematically searched up to November 16, 2016. STUDY SELECTION: Original data, analytic prospective design, physical therapy-led exercise intervention evaluation, children and adolescents with JIA, and assessment of functional, structural, activity, participation, or quality of life outcomes. DATA EXTRACTION: Two authors screened search results, and discrepancies were resolved by consensus. Of 5037 potentially relevant studies, 9 randomized controlled trials and 1 cohort study were included and scored. DATA SYNTHESIS: Study quality (Downs and Black quality assessment tool) and level of evidence (Oxford Centre of Evidence-Based Medicine model) were assessed and meta-analysis conducted where appropriate. Alternatively, a descriptive summary approach was chosen. All randomized controlled trials were moderate-quality intervention studies (level 2b evidence; median Downs and Black score, 20 out of 32; range, 15-27). Interventions included aquatic, strengthening, proprioceptive, aerobic, and Pilates exercises. Pediatric activity capacity (Child Health Assessment Questionnaire) improved with exercise (mean difference, .45; 95% confidence interval, .05-.76). Furthermore, descriptive summaries indicated improved activity capacity, body function and structure (pain and muscle strength), and quality of life outcomes. CONCLUSIONS: Exercise therapy appears to be well tolerated and beneficial across clinically relevant outcomes in patients with JIA. The paucity of high-quality evidence and study heterogeneity limited the ability to provide conclusive, generalizing evidence for the efficacy of exercise therapy and to provide specific recommendations for clinical practice at this time. Future research evaluating exercise program implementation using validated outcomes and detailed adherence and safety assessment is needed to optimize clinical decision pathways in patients with JIA.

Procedures for rat in situ skeletal muscle contractile properties.

There are many circumstances where it is desirable to obtain the contractile response of skeletal muscle under physiological circumstances: normal circulation, intact whole muscle, at body temperature. This includes the study of contractile responses like posttetanic potentiation, staircase and fatigue. Furthermore, the consequences of disease, disuse, injury, training and drug treatment can be of interest. This video demonstrates appropriate procedures to set up and use this valuable muscle preparation. To set up this preparation, the animal must be anesthetized, and the medial gastrocnemius muscle is surgically isolated, with the origin intact. Care must be taken to maintain the blood and nerve supplies. A long section of the sciatic nerve is cleared of connective tissue, and severed proximally. All branches of the distal stump that do not innervate the medial gastrocnemius muscle are severed. The distal nerve stump is inserted into a cuff lined with stainless steel stimulating wires. The calcaneus is severed, leaving a small piece of bone still attached to the Achilles tendon. Sonometric crystals and/or electrodes for electromyography can be inserted. Immobilization by metal probes in the femur and tibia prevents movement of the muscle origin. The Achilles tendon is attached to the force transducer and the loosened skin is pulled up at the sides to form a container that is filled with warmed paraffin oil. The oil distributes heat evenly and minimizes evaporative heat loss. A heat lamp is directed on the muscle, and the muscle and rat are allowed to warm up to 37°C. While it is warming, maximal voltage and optimal length can be determined. These are important initial conditions for any experiment on intact whole muscle. The experiment may include determination of standard contractile properties, like the force-frequency relationship, force-length relationship, and force-velocity relationship. With care in surgical isolation, immobilization of the origin of the muscle and alignment of the muscle-tendon unit with the force transducer, and proper data analysis, high quality measurements can be obtained with this muscle preparation.

Changes in tendon stiffness and running economy in highly trained distance runners.

The purpose of this study was to determine if changes in triceps-surae tendon stiffness (TST K) could affect running economy (RE) in highly trained distance runners. The intent was to induce increased TST K in a subgroup of runners by an added isometric training program. If TST K is a primary determinant of RE, then the energy cost of running (EC) should decrease in the trained subjects. EC was measured via open-circuit spirometry in 12 highly trained male distance runners, and TST K was measured using ultrasonography and dynamometry. Runners were randomly assigned to either a training or control group. The training group performed 4 × 20 s isometric contractions at 80% of maximum voluntary plantarflexion moment three times per week for 8 weeks. All subjects (V(O)2(max)) = 67.4 ± 4.6 ml kg(-1) min(-1)) continued their usual training for running. TST K was measured every 2 weeks. EC was measured in both training and control groups before and after the 8 weeks at three submaximal velocities, corresponding to 75, 85 and 95% of the speed at lactate threshold (sLT). Isometric training did neither result in a mean increase in TST K (0.9 ± 25.8%) nor a mean improvement in RE (0.1 ± 3.6%); however, there was a significant relationship (r(2) = 0.43, p = 0.02) between the change in TST K and change in EC, regardless of the assigned group. It was concluded that TST K and EC are somewhat labile and change together.

Economy of running: beyond the measurement of oxygen uptake.

The purpose of this study was to compare running economy across three submaximal speeds expressed as both oxygen cost (mlxkg(-1)xkm(-1)) and the energy required to cover a given distance (kcalxkg(-1)xkm(-1)) in a group of trained male distance runners. It was hypothesized that expressing running economy in terms of caloric unit cost would be more sensitive to changes in speed than oxygen cost by accounting for differences associated with substrate utilization. Sixteen highly trained male distance runners [maximal oxygen uptake (Vo(2max)) 66.5 +/- 5.6 mlxkg(-1)xmin(-1), body mass 67.9 +/- 7.3 kg, height 177.6 +/- 7.0 cm, age 24.6 +/- 5.0 yr] ran on a motorized treadmill for 5 min with a gradient of 0% at speeds corresponding to 75%, 85%, and 95% of speed at lactate threshold with 5-min rest between stages. Oxygen uptake was measured via open-circuit calorimetry. Average oxygen cost was 221 +/- 19, 217 +/- 15, and 221 +/- 13 mlxkg(-1)xkm(-1), respectively. Caloric unit cost was 1.05 +/- 0.09, 1.07 +/- 0.08, and 1.11 +/- 0.07 kcalxkg(-1)xkm(-1) at the three trial speeds, respectively. There was no difference in oxygen cost with respect to speed (P = 0.657); however, caloric unit cost significantly increased with speed (P < 0.001). It was concluded that expression of running economy in terms of caloric unit cost is more sensitive to changes in speed and is a more valuable expression of running economy than oxygen uptake, even when normalized per distance traveled.

The lactate minimum test for cycling: estimation of the maximal lactate steady state.

This study evaluated the reliability and validity of the lactate minimum test (LMT), an incremental test given after lactic acidosis was induced by sprint exercise. This test is purported to accurately estimate the intensity of exercise at which the transport of lactate into and out of the blood is in equilibrium (maximal lactate steady state or MLSS) and should be a good predictor of endurance performance. Fourteen athletes (mean age 27.2 +/- 3.7 yrs) completed the following on Kreitler rollers: (a) two 20-km time-trials (35.1 +/- 3.3 and 35.7 +/- 3.5 km.hr-1, p < .05); (b) two LMTs yielding lactate minimum speeds (LMS) of 33.6 +/- 3.4 and 33.4 +/- 3.1 km.hr-1 (p > 0.6); and (c) four constant intensity rides, at speeds bracketing the LMS. At 33.5 +/- 3.1 km.hr-1 plasma lactate concentration decreased 0.4 +/- 1.6 mM from 10 to 30 min. Plasma lactate increased 1.6 +/- 0.7 mM while riding 0.9 +/- 0.9 km.hr-1 faster. The LMT is a reliable (r2 = 0.904) and valid method to predict MLSS and a good predictor of endurance performance (LMT vs. 20-km time-trial, r2 = 0.86).