Chronic opioid use before and after exercise therapy and patient education among patients with knee or hip osteoarthritis.

OBJECTIVE: To investigate changes in opioid use after supervised exercise therapy and patient education among knee or hip osteoarthritis patients with chronic opioid use. METHOD: In this cohort study, we linked data from the Good Life with osteoArthritis in Denmark register (GLA:D®; standardised treatment program for osteoarthritis; January 2013 to November 2018) with national health registries. Among 35,549 patients, 1,262 were classified as chronic opioid users based on amount and temporal distribution of dispensed opioids the year before the intervention. We investigated changes in opioid use, measured as mg oral morphine equivalents (OMEQs), from the year before the intervention to the year after using generalized estimating equations. RESULTS: We found a 10% decrease in mg OMEQs from the year before to the year after the intervention (incidence rate ratio [IRR]: 0.90, 95% confidence interval [CI]: 0.86, 0.94). Additional analyses suggested this decrease to be mainly attributable to regulatory actions targeting opioid prescribing during the study period (IRR among patients participating in the intervention before: 0.98 [95% CI: 0.89, 1.07] vs after: 0.83 [0.74, 0.93] regulatory actions). In a random general population sample of matched chronic opioid users, a similar opioid use pattern was observed over time, further supporting the impact of regulatory actions on the opioid use in the study population. CONCLUSION: Among patients with knee or hip osteoarthritis and chronic opioid use, a standardised treatment program did not change opioid use when regulatory changes in opioid prescribing were taken into account.

Concurrent validity and intrarater reliability of two ultrasound-based methods for assessing patellar tendon stiffness.

INTRODUCTION: Assessment of tendon stiffness in vivo traditionally involves maximal muscle contractions, which can be challenging in pain populations. Alternative methods are suggested, although the clinimetric properties are sparse. This study investigated the concurrent validity and the intrarater reliability of two ultrasound-based methods for assessing patellar tendon stiffness. METHODS: Patellar tendon stiffness was assessed in 17 healthy adults with (a) the dynamometer and B-mode ultrasonography method (DBUS) and (b) the strain elastography method. Correlations between the two methods were analysed using Kendall's Tau-b. The relative reliability of both methods was evaluated using intraclass correlation coefficient (ICC). The absolute reliability was presented by Bland-Altman plots, standard error of measurement (SEM) and minimum detectable change (MDC). RESULTS: No correlation was found between the two methods, irrespective of reference tissue in strain elastography (Kendall's Tau-b Hoffa = -0.01 (p = 1.00), Kendall's Tau-b subcutis = 0.04 (p = 0.87)). Tracking of the tendon elongation in the DBUS method had good to excellent relative reliability (ICC = 0.95 (95% confidence interval - CI: 0.85-0.98)) and high absolute reliability (SEM = 0.04 mm (1%), MDC = 0.11 mm (3%)). The strain elastography method had good to excellent relative reliability, regardless of reference tissue (ICC Hoffa = 0.95 (95% CI: 0.86-0.98), ICC subcutis = 0.94 (95% CI: 0.82-0.98)), but low absolute reliability (SEM Hoffa = 0.06 (20%), MDC Hoffa = 0.18 (60%), SEM subcutis = 0.12 (41%), MDC subcutis = 0.32 (110%)). CONCLUSIONS: No concurrent validity existed for DBUS and strain elastography, suggesting that the two methods measure different tendon properties. The overall reliability for the DBUS method was high, but the absolute reliability was low for strain elastography stiffness ratios. Therefore, the strain elastography method may not be recommended for tracking differences in patellar tendon stiffness in healthy adults.

Knee and hip osteoarthritis are more alike than different in baseline characteristics and outcomes: a longitudinal study of 32,599 patients participating in supervised education and exercise therapy.

OBJECTIVE: Compare baseline characteristics and change in outcomes in patients with symptomatic knee or hip OA participating in patient education and exercise therapy. DESIGN: Longitudinal cohort study. Good Life with osteoArthritis in Denmark (GLA:D®) is an 8-week patient education and supervised exercise program delivered by certified clinicians. Changes in pain intensity, Knee injury/Hip disability Osteoarthritis Outcome Scores' subscale Quality of Life (K/HOOS QOL), EuroQoL 5-Dimensions 5-Level (EQ-5D) and 40 m walk test at ∼3 and 12 months were compared between knee and hip patients. RESULTS: 24,241 knee and 8,358 hip patients were included, with response rates of 75% and 60% at ∼3 and 12 months. Age, gender, symptom duration, pain medication use, pain intensity, physical function and quality of life were alike. More knee than hip patients were obese and had bilateral symptoms. At 3 months, clinically relevant improvements were seen in both knee and hip OA patients with clinically irrelevant between groups differences; 2.1 (1.5; 2.8) mm in pain intensity, -1.1 (-1.5; -0.7) point in K/HOOS QOL score, -0.010 (-0.013; -0.007) in EQ-5D index score and -0.02 (-0.02; -0.01) m/sec in walking speed. At 12 months the slight immediate differences were equalized. CONCLUSION: Patients presenting with knee and hip OA in primary care were on average more alike than different. Following treatment, clinically relevant improvements were seen in both knee and hip OA patients at 3 and 12 months. Patients with knee and hip OA should be prioritized alike for treatment with patient education and supervised exercise therapy.

Importance of patellofemoral and tibiofemoral cartilage lesions on trajectory of self-reported outcomes in patients at high risk of knee OA: 4-6 years follow-up of patients undergoing meniscal surgery.

OBJECTIVE: We evaluated whether patient-reported outcome trajectories (i.e., changes over time) differed by intraoperative compartmental cartilage lesion pattern over 4-6 years following arthroscopic meniscal surgery. METHODS: In this ancillary study of the Knee Arthroscopy Cohort Southern Denmark cohort, we intraoperatively categorized cartilage lesions as isolated patellofemoral, isolated tibiofemoral, or combined patellofemoral/tibiofemoral. Participants completed the Knee injury and Osteoarthritis Outcome Score (KOOS) pre-operatively, at 3 and 12 months, and at 4-6 years post-operatively and reported overall satisfaction at final follow-up. Our main outcome was KOOS4 (grand mean of four subscale means). We evaluated whether KOOS4 scores changed over time according to cartilage lesion patterns using adjusted mixed linear regression. We also estimated probability of treatment satisfaction using logistic regression. RESULTS: Of 630 participants with complete cartilage scores, 280 (44%) were women, mean (standard deviation) age was 49 (13) years, and BMI was 27.3 (4.4) kg/m2. KOOS4 scores at baseline were slightly lower in all lesion groups compared to the no lesion group, yet only the combined group was statistically significantly lower. KOOS4 trajectories were similar across cartilage lesion patterns, but by final follow-up, adjusted mean KOOS4 scores were 6.8 (95% CI 2.2, 11.4) to 9.8 (1.1, 18.5) points lower in groups with cartilage lesions compared to the no lesion group. Probability of patient-reported satisfaction did not differ statistically by group. CONCLUSIONS: Though KOOS4 scores were slightly lower in groups with arthroscopically assessed cartilage lesions compared to the no lesion group, trajectories were similar across all groups.

Inappropriate opioid dispensing in patients with knee and hip osteoarthritis: a population-based cohort study.

OBJECTIVE: To estimate inappropriate opioid dispensing in patients with knee or hip osteoarthritis (OA) defined as (1) dispensing of opioids within the first year of diagnosis or (2) long-term opioid use. DESIGN: Data from Skåne Healthcare Register was linked with the Swedish Prescribed Drug Register. Incidence proportion of dispensed opioids within first year of incident knee or hip OA diagnosis was determined in knee (n = 399,670) and hip (413,216) OA cohorts without a history of OA. The 1-year period prevalence of long-term opioid dispensing was determined in a prevalence cohort (n = 48,574 with knee and/or hip OA and n = 457,587 without OA). The proportion of OA patients with excess opioid dispensing attributable to OA was estimated using inverse probability weighted regression adjustment. RESULTS: In the incident cohorts, 5866 and 2359 developed knee and hip OA, respectively. Within the first year after OA diagnosis 14.7% patients with knee OA and 20.7% with hip OA had an opioid dispensed. The estimated inappropriate dispensing attributable to OA was 7.4% (95% CI 6.5-8.4) for knee OA and 12.8% (95% CI 11.1-14.4) for hip OA. Among persons with prevalent knee, hip or knee and hip OA inappropriate, long-term opioid use attributable to OA was 1.3%, 2.0% and 2.4% of, respectively. CONCLUSIONS: More than half the incident opioid dispensations to patients within their first year after knee or hip OA diagnosis are inappropriate according to current treatment guidelines. Furthermore, 2% of patients with prevalent knee or hip OA have inappropriate long-term dispensing of opioids.

Opioid use in knee or hip osteoarthritis: a region-wide population-based cohort study.

OBJECTIVE: To quantify opioid use in knee and hip osteoarthritis (OA) patients, and to estimate the proportion of opioids in the population attributable to OA patients. DESIGN: Population-based cohort study. METHODS: We included 751,579 residents in southern Sweden, aged ≥35 years in 2015. Doctor-diagnosed knee or hip OA between 1998 and 2015 was the exposure. Dispensed weak and strong opioids were identified between November 2013 and October 2015 from the Swedish Prescribed Drug Register (SPDR). We determined age- and sex-standardized 12-month period prevalence of opioid use from November 2014 until October 2015 and calculated prevalence ratios and incidence rate ratios adjusted for age, sex, and other socio-demographic variables. We estimated the population attributable fraction (PAF) of incident opioid use attributable to OA patients. RESULTS: The 12-month prevalence of opioid use among OA patients was 23.7% [95% confidence intervals (CI) 23.3-24.2], which was two-fold higher compared to individuals without knee or hip OA: prevalence ratio: 2.1 [95% CI 2.1-2.1]. Similarly, OA patients were more likely to have an incident opioid dispensation, especially for strong opioids (incidence rate ratio: 2.6 [95% CI 2.5-2.7]). Population attributable tractions (PAF) of incident opioid use attributable to OA patients was 12%, 9% for weak and 17% for strong opioids. CONCLUSIONS: Every fourth patient with knee or hip OA has opioids dispensed over a 1-year period, and 12% of incident opioid dispensations are attributable to OA and/or its related comorbidities. These results highlight that patients with knee and hip OA constitute a group of patients with an alarmingly high use of opioids.

Change in patient-reported outcomes in patients with and without mechanical symptoms undergoing arthroscopic meniscal surgery: A prospective cohort study.

OBJECTIVE: Patients with degenerative or traumatic meniscal tears are at high risk of developing knee osteoarthritis. We investigated if younger (≤40 years) and older (>40 years) patients with preoperative mechanical symptoms (MS) improved more in patient-reported outcomes after meniscal surgery than those without MS. DESIGN: Patients from Knee Arthroscopy Cohort Southern Denmark (KACS) undergoing arthroscopic surgery for a meniscal tear completed online questionnaires before surgery, and at 12 and 52 weeks follow-up. Questionnaires included self-reported presence of MS (i.e., sensation of catching and/or locking) and the Knee injury and Osteoarthritis Outcome Score (KOOS). We analyzed between-group differences in change in KOOS4 from baseline to 52 weeks, using an adjusted mixed linear model. RESULTS: 150 younger patients (mean age 31 (SD 7), 67% men) and 491 older patients (mean age 54 (SD 9), 53% men) constituted the baseline cohorts. Patients with MS generally had worse self-reported outcomes before surgery. At 52 weeks follow-up, younger patients with preoperative MS had improved more in KOOS4 scores than younger patients without preoperative MS (adjusted mean difference 10.5, 95% CI: 4.3, 16.6), but did not exceed the absolute postoperative KOOS4 scores observed for those without MS. No difference in improvement was observed between older patients with or without MS (adjusted mean difference 0.7, 95% CI: -2.6, 3.9). CONCLUSIONS: Younger patients (≤40 years) with preoperative MS experienced greater improvements after arthroscopic surgery compared to younger patients without MS. Our observational study result needs to be confirmed in randomized trials.

Changes in knee joint load indices from before to 12 months after arthroscopic partial meniscectomy: a prospective cohort study.

OBJECTIVE: Patients undergoing arthroscopic partial meniscectomy (APM) are at increased risk of knee osteoarthritis (OA). Meniscal damage and/or surgery may alter knee joint loading to increase OA risk. We investigated changes in knee joint loading following medial APM surgery, compared with the contra-lateral leg. METHODS: We estimated indices of knee joint loading (external peak knee adduction moment (KAM), KAM impulse and peak knee flexion moment (KFM)) normalized to body size (i.e., body mass (BM) and height (HT)) using 3D gait analysis in 23 patients (17 men, mean (SD) 46.2 (6.4) years, BMI 25.8 (3.4) kg/m(2)) without radiographic knee OA before and 12 months after medial APM. Static alignment was assessed by radiography and self-reported outcomes by Knee injury and Osteoarthritis Outcome Score (KOOS). RESULTS: Peak KAM and KAM impulse increased in the APM leg compared to the contra-lateral leg from before to 12 months after surgery (change difference: 0.38 Nm/BM*HT% 95% CI 0.01 to 0.76 (P = 0.049) and 0.20 Nm*s/BM*HT% 95% CI 0.10 to 0.30 (P < 0.001)). Patients self-reported improvements on all KOOS subscales (KOOS pain improvement: 22.8 95% CI 14.5 to 31.0 (P < 0.01)). CONCLUSIONS: A relative increase in indices of medial compartment loading was observed in the leg undergoing APM compared with the contra-lateral leg from before to 12 months after surgery. This increase may contribute to the elevated risk of knee OA in these patients. Randomized trials including a non-surgical control group are needed to determine if changes in joint loading following APM are caused by surgery or by changes in symptoms.

Pain trajectory and exercise-induced pain flares during 8 weeks of neuromuscular exercise in individuals with knee and hip pain.

OBJECTIVE: Patients considering or engaged in exercise as treatment may expect or experience transient increases in joint pain, causing fear of exercise and influencing compliance. This study investigated the pain trajectory during an 8-week neuromuscular exercise (NEMEX) program together with acute exercise-induced pain flares in persons with knee or hip pain. DESIGN: Individuals above 35 years self-reporting persistent knee or hip pain for the past 3 months were offered 8 weeks of supervised NEMEX, performed in groups twice weekly. The program consisted of 11 exercises focusing on joint stability and neuromuscular control. Participants self-reported joint pain on a 0-10 numerical rating scale (NRS) at baseline and 8-weeks follow-up. NRS pain ratings were also collected before and immediately after every attended exercise session. RESULTS: Joint pain was reduced from baseline (NRS 3.6; 95% CI 3.2-4.1) to 8-weeks follow-up (2.6; 95% CI 2.1-3.1), (P < 0.01). Pain decreased 0.04 NRS (95% CI 0.02-0.05, P < 0.01) on average per exercise session and pre- to post-exercise pain decreased 0.04 NRS (95% CI 0.03-0.05, P < 0.01) on average per session, approaching no acute exercise-induced pain in the last weeks. CONCLUSION: This study found a clear decrease in size of acute exercise-induced pain flares with increasing number of exercise sessions. In parallel, pain ratings decreased over the 8 weeks exercise period. Our findings provide helpful information for clinicians, which can be used to educate and balance patient expectation when starting supervised neuromuscular exercise.

Arthroscopic surgery for degenerative knee: systematic review and meta-analysis of benefits and harms.

OBJECTIVE: To determine benefits and harms of arthroscopic knee surgery involving partial meniscectomy, debridement, or both for middle aged or older patients with knee pain and degenerative knee disease. DESIGN: Systematic review and meta-analysis. MAIN OUTCOME MEASURES: Pain and physical function. DATA SOURCES: Systematic searches for benefits and harms were carried out in Medline, Embase, CINAHL, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL) up to August 2014. Only studies published in 2000 or later were included for harms. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Randomised controlled trials assessing benefit of arthroscopic surgery involving partial meniscectomy, debridement, or both for patients with or without radiographic signs of osteoarthritis were included. For harms, cohort studies, register based studies, and case series were also allowed. RESULTS: The search identified nine trials assessing the benefits of knee arthroscopic surgery in middle aged and older patients with knee pain and degenerative knee disease. The main analysis, combining the primary endpoints of the individual trials from three to 24 months postoperatively, showed a small difference in favour of interventions including arthroscopic surgery compared with control treatments for pain (effect size 0.14, 95% confidence interval 0.03 to 0.26). This difference corresponds to a benefit of 2.4 (95% confidence interval 0.4 to 4.3) mm on a 0-100 mm visual analogue scale. When analysed over time of follow-up, interventions including arthroscopy showed a small benefit of 3-5 mm for pain at three and six months but not later up to 24 months. No significant benefit on physical function was found (effect size 0.09, -0.05 to 0.24). Nine studies reporting on harms were identified. Harms included symptomatic deep venous thrombosis (4.13 (95% confidence interval 1.78 to 9.60) events per 1000 procedures), pulmonary embolism, infection, and death. CONCLUSIONS: The small inconsequential benefit seen from interventions that include arthroscopy for the degenerative knee is limited in time and absent at one to two years after surgery. Knee arthroscopy is associated with harms. Taken together, these findings do not support the practise of arthroscopic surgery for middle aged or older patients with knee pain with or without signs of osteoarthritis. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42014009145.

Arthroscopic surgery for degenerative knee: systematic review and meta-analysis of benefits and harms.

OBJECTIVE: To determine benefits and harms of arthroscopic knee surgery involving partial meniscectomy, debridement, or both for middle aged or older patients with knee pain and degenerative knee disease. DESIGN: Systematic review and meta-analysis. MAIN OUTCOME MEASURES: Pain and physical function. DATA SOURCES: Systematic searches for benefits and harms were carried out in Medline, Embase, CINAHL, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL) up to August 2014. Only studies published in 2000 or later were included for harms. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Randomised controlled trials assessing benefit of arthroscopic surgery involving partial meniscectomy, debridement, or both for patients with or without radiographic signs of osteoarthritis were included. For harms, cohort studies, register based studies, and case series were also allowed. RESULTS: The search identified nine trials assessing the benefits of knee arthroscopic surgery in middle aged and older patients with knee pain and degenerative knee disease. The main analysis, combining the primary endpoints of the individual trials from three to 24 months postoperatively, showed a small difference in favour of interventions including arthroscopic surgery compared with control treatments for pain (effect size 0.14, 95% confidence interval 0.03 to 0.26). This difference corresponds to a benefit of 2.4 (95% confidence interval 0.4 to 4.3) mm on a 0-100 mm visual analogue scale. When analysed over time of follow-up, interventions including arthroscopy showed a small benefit of 3-5 mm for pain at three and six months but not later up to 24 months. No significant benefit on physical function was found (effect size 0.09, -0.05 to 0.24). Nine studies reporting on harms were identified. Harms included symptomatic deep venous thrombosis (4.13 (95% confidence interval 1.78 to 9.60) events per 1000 procedures), pulmonary embolism, infection, and death. CONCLUSIONS: The small inconsequential benefit seen from interventions that include arthroscopy for the degenerative knee is limited in time and absent at one to two years after surgery. Knee arthroscopy is associated with harms. Taken together, these findings do not support the practise of arthroscopic surgery for middle aged or older patients with knee pain with or without signs of osteoarthritis. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42014009145.

Knee extensor muscle weakness is a risk factor for development of knee osteoarthritis. A systematic review and meta-analysis.

The objective of this study was to perform a systematic review and meta-analysis on the association between knee extensor muscle weakness and the risk of developing knee osteoarthritis. A systematic review and meta-analysis was conducted with literature searches in Medline, SPORTDiscus, EMBASE, CINAHL, and AMED. Eligible studies had to include participants with no radiographic or symptomatic knee osteoarthritis at baseline; have a follow-up time of a minimum of 2 years, and include a measure of knee extensor muscle strength. Hierarchies for extracting data on knee osteoarthritis and knee extensor muscle strength were defined prior to data extraction. Meta-analysis was applied on the basis of the odds ratios (ORs) of developing symptomatic knee osteoarthritis or radiographic knee osteoarthritis in subjects with knee extensor muscle weakness. ORs for knee osteoarthritis and 95% confidence intervals (CI) were estimated and combined using a random effects model. Twelve studies were eligible for inclusion in the meta-analysis after the initial searches. Five cohort studies with a follow-up time between 2.5 and 14 years, and a total number of 5707 participants (3553 males and 2154 females), were finally included. The meta-analysis showed an overall increased risk of developing symptomatic knee osteoarthritis in participants with knee extensor muscle weakness (OR 1.65 95% CI 1.23, 2.21; I(2) = 50.5%). This systematic review and meta-analysis showed that knee extensor muscle weakness was associated with an increased risk of developing knee osteoarthritis in both men and women.

Alterations in molecular muscle mass regulators after 8 days immobilizing Special Forces mission.

In military operations, declined physical capacity can endanger the life of soldiers. During special support and reconnaissance (SSR) missions, Special Forces soldiers sustain 1-2 weeks full-body horizontal immobilization, which impairs muscle strength and performance. Adequate muscle mass and strength are necessary in combat or evacuation situations, which prompt for improved understanding of muscle mass modulation during SSR missions. To explore the molecular regulation of myofiber size during a simulated SSR operation, nine male Special Forces soldiers were biopsied in m. vastus lateralis pre and post 8 days immobilizing restricted prone position. After immobilization, total mammalian target of rapamycin protein was reduced by 42% (P < 0.05), whereas total and phosphorylated protein levels of Akt, ribosomal protein S6k, 4E-BP1, and glycogen synthase kinase3ß were unchanged. Messenger RNA (mRNA) levels of the atrogenes forkhead box O3 (FoxO3), atrogin1, and muscle ring finger protein1 (MuRF1) increased by 36%, 53%, and 71% (P < 0.01), MuRF1 protein by 51% (P = 0.05), whereas FoxO1 and peroxisome proliferator-activated receptor γ coactivator-1 ß mRNAs decreased by 29% and 40% (P < 0.01). In conclusion, occupational immobilization in Special Forces soldiers led to modulations in molecular muscle mass regulators during 8 days prone SSR mission, which likely contribute to muscle loss observed in such operations. The present data expand our knowledge of human muscle mass regulation during short-term immobilization.

Range of motion, neuromechanical, and architectural adaptations to plantar flexor stretch training in humans.

The neuromuscular adaptations in response to muscle stretch training have not been clearly described. In the present study, changes in muscle (at fascicular and whole muscle levels) and tendon mechanics, muscle activity, and spinal motoneuron excitability were examined during standardized plantar flexor stretches after 3 wk of twice daily stretch training (4 × 30 s). No changes were observed in a nonexercising control group (n = 9), however stretch training elicited a 19.9% increase in dorsiflexion range of motion (ROM) and a 28% increase in passive joint moment at end ROM (n = 12). Only a trend toward a decrease in passive plantar flexor moment during stretch (-9.9%; P = 0.15) was observed, and no changes in electromyographic amplitudes during ROM or at end ROM were detected. Decreases in H(max):M(max) (tibial nerve stimulation) were observed at plantar flexed (gastrocnemius medialis and soleus) and neutral (soleus only) joint angles, but not with the ankle dorsiflexed. Muscle and fascicle strain increased (12 vs. 23%) along with a decrease in muscle stiffness (-18%) during stretch to a constant target joint angle. Muscle length at end ROM increased (13%) without a change in fascicle length, fascicle rotation, tendon elongation, or tendon stiffness following training. A lack of change in maximum voluntary contraction moment and rate of force development at any joint angle was taken to indicate a lack of change in series compliance of the muscle-tendon unit. Thus, increases in end ROM were underpinned by increases in maximum tolerable passive joint moment (stretch tolerance) and both muscle and fascicle elongation rather than changes in volitional muscle activation or motoneuron pool excitability.

Stretch-shortening cycle muscle power in women and men aged 18-81 years: Influence of age and gender.

This study explored the age-related deterioration in stretch-shortening cycle (SSC) muscle power and concurrent force-velocity properties in women and men across the adult life span. A total of 315 participants (women: n = 188; men: n = 127) aged 18-81 years performed maximal countermovement jumps on an instrumented force plate. Maximal SSC leg extension power expressed per kg body mass (Ppeak) was greater in men than in women across the adult age span (P < 0.001); however, this gender difference was progressively reduced with increasing age, because men showed an ∼50% faster rate of decline in SSC power than women (P < 0.001). Velocity at peak power (VPpeak) was greater in men than in women (P < 0.001) but declined at a greater rate in men than in women (P = 0.002). Vertical ground reaction force at peak power (FPpeak) was higher in men than in women in younger adults only (P < 0.001) and the age-related decline was steeper in men than in women (P < 0.001). Men demonstrated a steeper rate of decline in Ppeak than women with progressive aging. This novel finding emerged as a result of greater age-related losses in men for both force and velocity. Consequently, maximal SSC power production was observed to converge between genders when approaching old age.

Changes in muscle strength and morphology after muscle unloading in Special Forces missions.

The purpose of the present study was to determine the changes in maximal muscle strength, rapid force capacity, jumping performance and muscle morphology following a Special Forces military operation involving 8 days of muscle unloading. Nine male Special Forces soldiers were tested before (pre) and immediately after (post1) an 8-day simulated special support and reconnaissance (SSR) mission and after 3 h of active recovery (post2). Maximal muscle strength (MVC) and rate of force development (RFD) were measured along with maximal counter movement jump height (JH). Muscle biopsies were obtained from the vastus lateralis at pre and post1. Acute reductions were found in MVC (11%), JH (10%) and RFD (17-22%) after 8 days of muscle unloading (post1) (P≤0.05). Type IIX fiber type area% increased (P≤0.05) at post1 together with a tendency toward increased type IIX fiber type % (P=0.09) and decreased type I fiber type % (P=0.06), suggesting a transition toward a less fatigue-resistant fiber-type profile. In conclusion, short-term unloading during SSR missions led to marked reductions in mechanical muscle function and functional performance, which may be partly explained by the changes in muscle morphology. Future studies should identify intervention strategies to counter-act the observed impairments.

Rapid muscle force capacity changes after soccer match play.

The present study examined the fatigue development in muscle mechanical properties with emphasis on rapid force characteristics and neuromuscular activity in response to high level soccer match play. Young elite soccer players (n=9) were tested before (CON) and after (POST) a soccer match for maximal knee extensor and flexor isometric strength (MVC) and contractile rate of force development (RFD) with synchronous surface electromyography (EMG) recording. Furthermore, maximal vertical jump power and related parameters were assessed. Isometric knee extensor and flexor MVC decreased approximately 10% (p< or =0.01) along with a right-shift in the moment-time curve. RFD decreased approximately 9% (0-200 ms) for the knee flexors while there was a tendency towards reduced RFD during knee extension following soccer match play. Similar reductions were observed for some but not all selected EMG parameters during the MVC and RFD tests. Mechanical jump parameters generally remained unchanged post match play. This study is the first to examine the fatigue induced changes in rapid muscle force production (RFD) induced by soccer match play. The observed decrement in rapid muscle force capacity is likely to have negative impact on performance in explosive playing actions (i.e. accelerations, kicking, sprinting) that typically is involved in soccer match play.

Acute fatigue-induced changes in muscle mechanical properties and neuromuscular activity in elite handball players following a handball match.

The purpose of the present study was to determine the acute fatigue development in muscle mechanical properties and neuromuscular activity in response to handball match play. Male elite handball players (n = 10) were tested before and after a simulated handball match for maximal isometric strength [maximal voluntary contraction (MVC)] and rate of force development (RFD) with synchronous electromyography (EMG) recording, while maximal vertical jump parameters were assessed using force plate analysis. Quadriceps and hamstrings MVC and RFD decreased significantly post-match (approximately 10%, P < 0.05 and approximately 16-21%, P < 0.05, respectively). During quadriceps, MVC mean EMG amplitude [mean average voltage (MAV)] decreased for the vastus lateralis (VL) and rectus femoris (RF) (21-42%, P < or = 0.05), while MAV also decreased in the antagonist biceps femoris (BF) muscle (48-55%, P < 0.01). During hamstring MVC, MAV was reduced in BF (31%, P < 0.01). Maximum EMG amplitude during quadriceps MVC was reduced for the VL (28%, P < 0.01) and the RF (5%, P < 0.05). During hamstring MVC, maximum EMG was reduced for BF (21%, P < 0.01). Post-match maximal jump height was reduced (5.2%, P < 0.01), as was also work (6.8%, P < 0.01), velocity of center of mass (2.4-4.0%, P < 0.01) and RFD (approximately 30%, P < 0.05). In conclusion, maximal (MVC) and rapid muscle force characteristics (RFD, impulse) were acutely affected concurrently with marked reductions in muscle EMG following handball match play, which may potentially lead to impaired functional performance.