In the heat of the moment: the effects of extreme temperatures on the cognitive functioning of firefighters.

Exposure to high temperatures can have detrimental effects on cognitive processing and this is concerning for firefighters who routinely work in extreme temperatures. Whilst past research has studied the effects of heat on firefighter cognition, findings are mixed, and no work has measured the time course of cognitive recovery. This study compared working memory, vigilance, and cognitive flexibility of 37 firefighters before and after they engaged in a live-fire training exercise with temperatures exceeding 115 °C. To assess recovery, cognition was measured on exiting the fire, then 20- and 40-minutes post-fire. Results showed impaired vigilance and cognitive flexibility (increased errors, slower responses) immediately after the fire, but recovery at 20-minutes. These findings indicate that a live indoor fire negatively impacts cognitive processing, but this effect is relatively short-lived and return to baseline functioning is seen 20-minutes after exiting the fire. The findings could be used to inform re-entry and cooling decisions.

Acute heat stress may affect cognitive processing, posing a health and safety risk to firefighters. This study demonstrates impaired cognition following a firefighter training exercise in temperatures exceeding 115 °C. Cognition recovered as core body temperature returned to normal, providing evidence for a 20-minute cooling period following exposure to extreme heat.

The acute effects of higher versus lower load duration and intensity on morphological and mechanical properties of the healthy Achilles tendon: a randomized crossover trial.

The Achilles tendon (AT) exhibits volume changes related to fluid flow under acute load which may be linked to changes in stiffness. Fluid flow provides a mechanical signal for cellular activity and may be one mechanism that facilitates tendon adaptation. This study aimed to investigate whether isometric intervention involving a high level of load duration and intensity could maximize the immediate reduction in AT volume and stiffness compared with interventions involving a lower level of load duration and intensity. Sixteen healthy participants (12 males, 4 females; age 24.4±9.4 years, body mass 70.9±16.1 kg, height 1.7±0.1 m) performed three isometric interventions of varying levels of load duration (2 s and 8 s) and intensity (35% and 75% maximal voluntary isometric contraction) over a 3 week period. Freehand 3D ultrasound was used to measure free AT volume (at rest) and length (at 35%, 55% and 75% of maximum plantarflexion force) pre- and post-interventions. The slope of the force-elongation curve over these force levels represented individual stiffness (N mm-1). Large reductions in free AT volume and stiffness resulted in response to long-duration high-intensity loading whilst less reduction was produced with a lower load intensity. In contrast, no change in free AT volume and a small increase in AT stiffness occurred with lower load duration. These findings suggest that the applied load on the AT must be heavy and sustained for a long duration to maximize immediate volume reduction, which might be an acute response that enables optimal long-term tendon adaptation via mechanotransduction pathways.

Immediate and Short-Term Effects of Short- and Long-Duration Isometric Contractions in Patellar Tendinopathy.

OBJECTIVES: Isometric muscle contractions are used in the management of patellar tendinopathy to manage pain and improve function. Little is known about whether long- or short-duration contractions are optimal to improve pain. This study examined the immediate and short-term (4 weeks) effects of long- and short-duration isometric contraction on patellar tendon pain, and tendon adaptation. DESIGN: Repeated measures within groups. SETTING: Clinical primary care. PATIENTS: Participants (n = 16, males) with patellar tendinopathy. INTERVENTION: Short-duration (24 sets of 10 seconds) or long-duration (6 sets of 40 seconds) isometric knee extension loading (85% maximal voluntary contraction), for 4 weeks. MAIN OUTCOME MEASURE: Immediate change in pain with single-leg decline squat (SLDS) and hop, as well as change in pain and tendon adaptation [within-session anterior-posterior (AP) strain] were assessed over 4 weeks. RESULTS: Pain was significantly reduced after isometric loading on both SLDS (P < 0.01) and hop tests (P < 0.01). Pain and quadriceps function improved over the 4 weeks (P < 0.05). There was significant AP strain at each measurement occasion (P < 0.01). Although transverse strain increased across the training period from ∼14% to 22%, this was not significant (P = 0.08). CONCLUSIONS: This is the first study to show that short-duration isometric contractions are as effective as longer duration contractions for relieving patellar tendon pain when total time under tension is equalized. This finding provides clinicians with greater options in prescription of isometric loading and may be particularly useful among patients who do not tolerate longer duration contractions. The trend for tendon adaptation over the short 4-week study period warrants further investigation.

Fish oil supplementation, resting blood flow and markers of cellular metabolism during incremental exercise.

Dietary supplementation of fish oils (n-3 PUFA) have been observed to affect insulin action and hence metabolism, affecting the ability to carry out work. Here we examine the effects of fish oil supplementation in conjunction with a glucose load during exertion, on markers of substrate utilization. A pre-test, post-test design was performed on ten healthy young males to assess the effects of 4 weeks fish oil supplementation on muscle metabolism during incremental exertion. Breath-by-breath analysis for respiratory exchange ratio (RER) along with blood lactate and blood glucose were determined at baseline, during exercise following an acute glucose bolus (10% solution at 4 mL/kg/bw), and again following supplementation of 4.2 g.day(-1) (2.2 g EPA, 1.4 g DHA). To examine the effect of fish oil on blood flow, Doppler ultrasound was used to assess femoral blood flow at rest. Following consumption of fish oils, exercising blood glucose and RER were seen to change significantly (4.66±0.44 vs. 4.58±0.31 mmol.L(-1) and 0.97±0.03 vs. 0.99±0.04; p<0.05). Resting femoral arterial blood flow was seen to increase significantly (p<0.05) pre- to post- test; 0.26±0.02-0.30±0.03 L.min(-1). Specific population groups such as those undertaking high-intensity exercise, and clinical groups such as intermittent claudicants, may benefit from the effects of fish oil supplementation.

Scaling--which methods best predict performance?

Athletes with a higher body mass (BM) tend to be stronger, with ratio scaling possibly eliminating this effect. The aim of this study was to compare relationships between sprint performances with scaled measures of strength and power. Fifteen professional rugby league players (age, 26.27 6 3.87 years; height, 183.33 6 6.37 cm; BM, 96.86 6 11.49 kg) performed 1 repetition maximum back squats, power cleans, squat jumps, and sprints (5, 10, and 20 m). Heavier athletes (forward) generated significantly greater absolute levels of power during the squat jump (5,659.11 6 710.35 vs.4,740.16 6 558.61 W; p , 0.001); however, when power data were scaled no differences were observed. Squat performance indicated no differences in absolute ability between the subgroups (190.6 6 14.25 vs. 205.7 6 18.35 kg), although the lighter group was significantly (p # 0.05) stronger than the heavier group when using ratio and allometric methods (2.1 vs. 1.9 kg · kg(-1) and 10.42 vs. 9.87 kg · kg(0.28)), respectively. Significant relationships with 5-m sprints were only observed for ratio and allometrically scaled power cleans (r = 20.625, p , 0.02; r = 20.675, p , 0.02), with similar correlations between allometrically scaled 10-m sprint and both back squat and power clean performances. Scaled power clean performances were also inversely correlated with 20-m sprints (r = 20.620, r = 20.638, p , 0.02). Where differences in absolute strength are apparent between individuals of different BM, then the use of scaling is required. Because of the similarity between ratio and allometric methods, simple ratio scaling is recommended.

The use of normalized cross-correlation analysis for automatic tendon excursion measurement in dynamic ultrasound imaging.

The work describes an automated method of tracking dynamic ultrasound images using a normalized cross-correlation algorithm, applied to the patellar and gastrocnemius tendon. Displacement was examined during active and passive tendon excursions using B-mode ultrasonography. In the passive test where two regions of interest (2-ROI) were tracked, the automated tracking algorithm showed insignificant deviations from relative zero displacement for the knee (0.01 ± 0.04 mm) and ankle (-0.02 ± 0.04 mm) (P > .05). Similarly, when tracking 1-ROI the passive tests showed no significant differences (P > .05) between automatic and manual methods, 7.50 ± 0.60 vs 7.66 ± 0.63 mm for the patellar and 11.28 ± 1.36 vs 11.17 ± 1.35 mm for the gastrocnemius tests. The active tests gave no significant differences (P > .05) between automatic and manual methods with differences of 0.29 ± 0.04 mm for the patellar and 0.26 ± 0.01 mm for the gastrocnemius. This study showed that automatic tracking of in vivo displacement of tendon during dynamic excursion under load is possible and valid when compared with the standardized method. This approach will save time during analysis and enable discrete areas of the tendon to be examined.

Does resistance training ameliorate cancer-related fatigue in cancer survivors? A systematic review with meta-analysis.

PURPOSE: Cancer-related fatigue (CRF) is unrelenting. As neither rest nor sleep ameliorates cognitive, emotional, and physical symptoms, quality of life is diminished. This study examines resistance training (RT) effectiveness on CRF in cancer survivors. The secondary aims were to identify the dose-response relationship of RT frequency, intensity, and volume on CRF in different cancer survivor populations. MATERIALS AND METHODS: Systematic searches via numerous databases for RCTs were performed in June 2022. Patient-reported outcome measures (PROM), were analysed, pre-to-post intervention, using a random-effects model. The Physiotherapy Evidence Database (PEDro) scale informed methodological quality assessment. RESULTS: Eight studies were included (cancer survivors: breast (BCS) = 5; endometrial (ECS) = 1; prostate (PCS) = 2). Overall, RT interventions ≥ 6 weeks elicited large significant reductions in CRF for FACIT-F (SMD = 0.932, p = <0.001) and moderate significant reductions in CRF for PFS-R (SMD = -0.622, p = 0.004). CONCLUSION: Main findings indicate that RT ameliorates CRF, especially in BCS; however, individualised approaches should be advocated. Supervised training elicited the greatest positive outcomes, thus should be a pivotal part of the cancer rehabilitation pathway. Future studies should be adequately powered, undertake discrete analyses of different cancer types, and investigate chronic RT effects.

Cancer-related fatigue (CRF) is debilitating and distressing, leading to reduced quality of life and function in cancer survivors.Considerable heterogeneity exists in disease histology and clinical patient presentation.Individualised resistance training (RT) is an effective, safe, and accessible intervention to mitigat:e fatigue levels, thus aid function, most notably in breast cancer survivors.

The relationship between psychological, cognitive, and contextual factors and rehabilitation outcomes in Achilles tendinopathy: A prospective feasibility cohort study.

OBJECTIVES: This study aimed to investigate the feasibility of conducting a full-scale study investigating the influence of patient-related factors on rehabilitation outcomes in Achilles tendinopathy (AT). A secondary aim was to investigate preliminary relationships between patient-related factors and clinical outcomes at 12- and 26- weeks. DESIGN: feasibility cohort. SETTING: Australian healthcare settings. METHODS: Participants with AT receiving physiotherapy in Australia were recruited via treating physiotherapists and online. Data were collected online at baseline, 12- and 26-weeks. Progression criteria for a full-scale study were recruitment rate of ≥10 per month, conversion rate ≥20%, and response rate to questionnaires ≥80%. The relationship between patient-related factors and clinical outcomes was investigated using Spearman's rho correlation coefficient. RESULTS: The average recruitment rate was 5/month, conversion rate was 97%, and response rate to questionnaires was ≥97% at all timepoints. There was a fair to moderate correlation (rho = 0.225 to 0.683) between patient-related factors and clinical outcomes at the 12-week, but no to weak correlation at the 26-week (rho = 0.002 to 0.284). CONCLUSIONS: Feasibility outcomes suggest a future full-scale cohort study is feasible with the caveat of utilizing strategies to improve recruitment rate. Preliminary bivariate correlations at 12-weeks warrant further investigations in larger studies.

Do extreme temperatures affect cognition? A short review of the impact of acute heat stress on cognitive performance of firefighters.

Research shows that exposure to high environmental temperatures can affect task performance. Theoretical explanations outline that heat is a source of stress that competes for limited-capacity resources, therefore if a task is resource-intensive, and/or if heat stress is extreme, performance will suffer. One occupation in which individuals complete demanding tasks and make difficult decisions, often in temperatures exceeding 200°C, is firefighting. Yet very little is currently known about the impact of heat stress on the cognitive functioning of firefighters. This short review summarizes the limited research in this area, focusing on studies that measured cognition of firefighters following a realistic training exercise. The findings are mixed with evidence that heat stress improves, impairs, and has no impact on cognitive functioning. While there are differences in the firefighting activities utilized, and the temperatures that participants were exposed to, it is argued that the varied findings can be attributed to the tasks used to assess cognitive processing, and the cognitive functions being measured. In accordance with the wider field of research, it is concluded that complex functioning, such as sustained attention, vigilance, and working memory is negatively impacted by acute exposure to extreme heat. Greater understanding of factors affecting cognition would inform safety practices and more research is needed to understand how and when heat stress may influence cognition in firefighting scenarios.

A comparison of maximal squat strength and 5-, 10-, and 20-meter sprint times, in athletes and recreationally trained men.

The purpose of this study was to identify whether there was a relationship between relative strength during a 1 repetition maximum (1RM) back squat and 5-, 10-, and 20-m sprint performances in both trained athletes and recreationally trained individuals. Professional rugby league players (n = 24) and recreationally trained individuals (n = 20) participated in this investigation. Twenty-meter sprint time and 1RM back squat strength, using free weights, were assessed on different days. There were no significant (p ≥ 0.05) differences between the well-trained and recreationally trained groups for 5-m sprint times. In contrast, the well-trained group's 10- and 20-m sprint times were significantly quicker (p = 0.004; p = 0.002) (1.78 + 0.06 seconds; 3.03 + 0.09 seconds) compared with the recreationally trained group (1.84 + 0.07 seconds; 3.13 + 0.11 seconds). The athletes were significantly stronger (170.63 + 21.43 kg) than the recreationally trained individuals (135.45 + 30.07 kg) (p = 0.01); however, there were no significant differences (p > 0.05) in relative strength between groups (1.78 + 0.27 kg/kg; 1.78 + 0.33 kg/kg, respectively). Significant negative correlations were found between 5-m sprint time and relative squat strength (r = -0.613, power = 0.96, p = 0.004) and between relative squat strength and 10- and 20-m sprint times in the recreationally trained group (r = -0.621, power = 0.51, p = 0.003; r = -0.604, power = 0.53, p = 0.005, respectively). These results, indicating that relative strength, are important for initial sprint acceleration in all athletes but more strongly related to sprint performance over greater distances in recreationally trained individuals.

The effect of resistance training on functional capacity in middle-aged to elderly individuals with peripheral artery disease: a meta-analysis.

INTRODUCTION: Peripheral artery disease (PAD) is an ischemic disease of the lower limbs, caused by atherosclerotic plaques, leading to impairments in functional capacity and reduced quality of life. This meta-analysis aimed to assess the effect of 12-week and 24-week resistance training (RT) interventions on 6-minute walking distance (6WMD) and initial claudication distance (ICD) measured during a 6-minute walk test (6MWT). EVIDENCE ACQUISITION: A meta-analysis was conducted in accordance with PRISMA guidelines, with an electronic search conducted using the online database of PUBMED. Methodological quality of all included studies was completed using a modified version of the Newcastle Ottawa Scale (NOS). The effect sizes (ES) of 6MWD and ICD were calculated, with the 12-week and 24-week interventions analyzed separately. EVIDENCE SYNTHESIS: An initial literature search yielded 1973 results that were consequently reduced to 7 studies to be included in the final meta-analysis. The pooled effect size for 6MWD for 12-week and 24-week interventions was ES=0.189 [95% CI: -0.074 to 0.451] P=0.159 and ES=0.298 [95% CI: -0.036 to 0.631] P=0.080 respectively. For ICD, ES=0.498 [95% CI: 0.000 to 0.995] P=0.050 and ES: 1.106 [95% CI: 0.120 to 0.428] P=0.001 respectively. CONCLUSIONS: Short-term RT interventions have a positive effect on functional capacity in middle-aged to elderly individuals with PAD. There was a greater effect on ICD compared to 6MWD, with 24-week interventions showing larger effects for both measures. Improvements in functional capacity in such populations confers significant potential for positive health outcomes.

Comparisons of Core Temperature Between a Telemetric Pill and Heart Rate Estimated Core Temperature in Firefighters.

Background: Firefighters may experience high environmental temperatures or carry out intensive physical tasks, or both, which leads to increased core body temperature and risk of fatalities. Hence there is a need to remotely and non-invasively monitor core body temperature. Methods: Estimated (heart rate algorithm) and actual core body temperature (ingested telemetric pill) measures were collected simultaneously for comparison during training exercises on 44 firefighter volunteers. Results: Prediction of core body temperature varied, with no specific identifiable pattern between the algorithm values and directly measured body core temperatures. Group agreement of Lin's Concordance of 0.74 (95% Upper 0.75, lower CI 0.73), was deemed poor. Conclusion: From individual agreement data Lin's Concordance was variable (Min 0.11, CI 0.13-0.01; Max 0.83, CI 0.86-0.80), indicating that the heart rate algorithm approach was not suitable for core body temperature monitoring in this population group, especially at the higher more critical core body temperatures seen.

An electromyographical comparison of trunk muscle activity during isometric trunk and dynamic strengthening exercises.

The purpose of this study was to compare rectus abdominis and erector spinae muscle activity during isometric (prone bridge [PB] and superman [SM]) and dynamic strengthening exercises (back squat, front squat [FS], and military press). Participants (n = 10, age 21.8 ± 2.6 years; body mass 82.65 ± 10.80 kg, 174.5± 7.2 cm), performed each exercise in a randomized order, using a repeated-measures design. Electromyographical (EMG) activity (sampling at 2,000 Hz) of the rectus abdominis (RA) and the erector spinae (ES) muscles was recorded throughout the duration of the exercises. Intraclass correlations demonstrated the highest levels of reliability for muscle activity during the isometric exercises; however, all exercises demonstrated high level of reliability (r = 0.764-0.998, p ≤ 0.01). The PB demonstrated significantly greater (p < 0.01) RA activity compared to all other exercises. The ES activity was significantly (p < 0.01) greater during the FS (1.010 ± 0.308 root mean square value [RMS (V)]) and SM (0.951 ± 0.217 RMS[V]) and compared to all other exercises, although there was no significant difference (p > 0.05) between the FS and the SM exercise. The PB may be the most suitable exercise for strengthening the RA, compared to dynamic exercises at a low to moderate load, because of a higher level of muscle activity. The FS may be a useful alternative to isometric exercises when strengthening the ES, because it results in slightly higher muscle activity levels when using only a light to moderate load. Because of the dynamic nature of the FS, this may also be more beneficial in transferring to activities of daily living and sporting environments.

Hypocalcaemia in pharyngolaryngectomy: Preservation or autotransplantation of parathyroid glands.

OBJECTIVE: To describe transient and permanent hypocalcaemia following partial and total pharyngolaryngectomy with parathyroid gland preservation or autotransplantation. METHODS: Thirty patients underwent partial or total pharyngolaryngectomy by a single surgeon during the period 2009-2020. Intraoperative parathyroid gland preservation or autotransplantation (where the gland appeared devascularized) was routinely performed. Calcium levels performed on day 1, 3 months, and at 12 months postoperatively were collected. Rates of transient and permanent hypocalcaemia were calculated. RESULTS: A total of 13% of patients had transient hypocalcaemia, and 10% permanent hypocalcaemia. Rates of transient and permanent hypocalcaemia in total pharyngolaryngectomy were 14% and 14%, respectively. Partial pharyngectomy hypocalcaemia rates were 13% for transient and 0% for permanent. The majority of patients underwent salvage surgery for oncological resection, often following radiotherapy (63%). Ipsilateral hemithyroidectomy was preferred to total (57% vs 7%), with high rates of concurrent neck dissection (67%) and reconstruction (87%). CONCLUSION: This data supports preservation or autotransplantation of parathyroid glands as a means of reducing permanent postoperative hypocalcaemia. LEVEL OF EVIDENCE: Level IV, case series, retrospective.

Patellar tendon properties with fluctuating menstrual cycle hormones.

Debate continues over whether skeletal muscle performance and injury risk vary over the course of the menstrual cycle. Alterations in tendon properties may play a role in the potential fluctuations of both of these variables. The aim of the current study was to determine any association between menstrual cycle phase and corresponding levels of female sex hormones and tendon properties. Fifteen normally menstruating (28-32-day cycles) healthy females (age 23 +/- 1 years, mass 63.1 +/- 2.6 kg, height 1.66 +/- 0.02 m) not taking any form of hormonal contraceptive took part in this study. In vivo patellar tendon properties and associated circulating hormonal levels were assessed on 3 occasions including days 3 +/- 0.4, 13 +/- 0.2, and 21 +/- 0.3. Dynamometry, ultrasonography, electromyography, and biochemical assessment of circulating levels of estradiol and progesterone were utilized. No significant differences were seen in tendon mechanical properties among the 3 phases of the menstrual cycle (p > 0.05). Regressions were carried out and revealed that estrogen and maximal voluntary tendon force explained 17.8% (p = 0.043) of the variance in young's modulus. Our findings link estrogen to a chronic, rather than an acute, impact on tendon behavior. These findings are relevant to clinical outcomes, exercise performance, and injury risk. In terms of tendon properties, menstrual cycle phase does not necessarily need to be considered when organizing training and competition schedules.

Time-of-day effect on patella tendon stiffness alters vastus lateralis fascicle length but not the quadriceps force-angle relationship.

AIM: To examine the time-of-day (TOD) effect on torque-force/angle, fibre length (FL), tendon stiffness (K), stress, and strain using the quadriceps muscle-tendon complex as a model. METHODS: Twelve healthy young men (aged 27+/-2.0 years) were studied at AM (7h45) and PM (5h45). Maximal isometric contractions were carried out on an isokinetic dynamometer, with real-time recordings of vastus lateralis (VL) FL and patella tendon K using B-mode ultrasonography. Percutaneous electrical twitch doublets superimposed on maximal torque were used to test for muscle activation capacity (AC). RESULTS: At PM, torque and force increased by 16+/-3.0% (P<0.01) over 30-90 degrees knee angles. Where the load was standardised (at 250N) in order to discriminate between torque generation capacity and tendon K changes, PM relative to AM, there were 8% and 13% (P<0.01) reductions in relaxed and contracted FL, respectively. Average K decreased by 21% (P<0.001) and the maximal stress and strain were increased at PM by 11% and 16%, respectively (P<0.01). No TOD effect on AC was seen. CONCLUSION: The quadriceps torque or force-angle relationships shift upwards at PM vs. AM, with no shift in the position of the optimal knee angle. This torque or force increase appears not to be centrally modulated. Although K decreases with TOD thereby potentially shortening the working length of the sarcomeres, these changes overall do not affect the ability of the muscle to produce greater torque in the evening.

Creep and the in vivo assessment of human patellar tendon mechanical properties.

BACKGROUND: Owing to the viscoelastic nature of tendons it may be that the total excursion and hence strain experienced by the tendon under load may be affected by the duration of contraction. Here we examine the effect of contraction duration on the measured in vivo mechanical properties of the patellar tendon. METHODS: Nine healthy young men aged 21 (SEM 0.5 years) performed three short (3-4s) and three long (10-12s) maximal ramped isometric contractions on an isokinetic dynamometer, with real-time recordings of patellar excursions using B-mode ultrasonography synchronised with forces to determine tendon mechanical properties. FINDINGS: Maximal patellar excursion was approximately 42% (P<0.001, effect size (r)=0.9) lower for the short 3.6 (SEM 0.4mm) vs. the long 6.2 (SEM 0.4mm) contractions. Similarly, across the range of forces tested, strain was approximately 42% (P<0.001, r=0.9) lower for the short vs. the long contractions 4.5 (SEM 0.5) vs. 8.0 (SEM 0.9%), respectively. Tendon stiffness however, was approximately 77% greater (4648 SEM 434 vs. 2633 SEM 257 N mm(-1), P<0.001, r=0.9) for short vs. long contractions. INTERPRETATION: Contraction duration significantly affects tendon strain and associated measures of stiffness at all levels of force. The implications of this finding are twofold in that the results: (a) indicate that in order to compare tendon mechanical properties within or across studies, duration of contraction must be standardised and (b) have possible implications on training protocols and associated injury risks.

Changes in tendon spatial frequency parameters with loading.

To examine and compare the loading related changes in micro-morphology of the patellar tendon. Fifteen healthy young males (age 19±3yrs, body mass 83±5kg) were utilised in a within subjects matched pairs design. B mode ultrasound images were taken in the sagittal plane of the patellar tendon at rest with the knee at 90° flexion. Repeat images were taken whilst the subjects were carrying out maximal voluntary isometric contractions. Spatial frequency parameters related to the tendon morphology were determined within regions of interest (ROI) from the B mode images at rest and during isometric contractions. A number of spatial parameters were observed to be significantly different between resting and contracted images (Peak spatial frequency radius (PSFR), axis ratio, spatial Q-factor, PSFR amplitude ratio, and the sum). These spatial frequency parameters were indicative of acute alterations in the tendon micro-morphology with loading. Acute loading modifies the micro-morphology of the tendon, as observed via spatial frequency analysis. Further research is warranted to explore its utility with regard to different loading induced micro-morphological alterations, as these could give valuable insight not only to aid strengthening of this tissue but also optimization of recovery from injury and treatment of conditions such as tendinopathies.

Patellar tendon in vivo regional strain with varying knee angle.

PURPOSE: Descriptive data on the aspects of site specific in vivo tendon strain with varying knee joint angle are non-existent. The present study determines and compares surface and deep layer strain of the patellar tendon during isometric contractions across a range of knee joint angles. METHODS: Male participants (age 22.0±3.4) performed ramped isometric knee extensions at knee joint angles of 90°, 70°, 50° and 30° of flexion. Strain patterns of the anterior and posterior regions of the patellar tendon were determined using real-time B-mode ultrasonography at each knee joint angle. Regional strain measures were compared using an automated pixel tracking method. RESULTS: Strain was seen to be greatest for both the anterior and posterior regions with the knee at 90° (7.76±0.89% and 5.06±0.76%). Anterior strain was seen to be significantly greater (p<0.05) than posterior strain for all knee angles apart from 30°, 90°=(7.76vs. 5.06%), 70°=(4.77vs. 3.75%), and 50°=(3.74vs. 2.90%). The relative strain (ratio of anterior to posterior), was greatest with the knee joint angle at 90°, and decreased as the knee joint angle reduced. CONCLUSIONS: The results from this study indicate that not only are there greater absolute tendon strains with the knee in greater flexion, but that the knee joint angle affects the regional strain differentially, resulting in greater shear between the tendon layers with force application when the knee is in greater degrees of flexion. These results have important implications for rehabilitation and training.

Power output and muscle myosin heavy chain composition in young and elderly men.

PURPOSE: Aging is associated with a decline in muscle volume, power output, and the velocity at which peak power (Vopt) occurs. The current study aimed to examine the relationship between lower-limb power output characteristics, muscle myosin heavy chain (MHC) composition, and lean limb volume. METHODS: Lower-limb power output during repeated efforts on an inertial sprint cycle and single-leg thrusts on the modified Nottingham power rig was studied in seven young and seven old males in relation to muscle MHC isoform composition of the vastus lateralis. RESULTS: Older subjects produced significantly lower power outputs and Vopt under all conditions (P < 0.01) and had lower proportions of fast MHC isoforms (P< 0.05). Peak power output during cycling was significantly related to lower-limb lean volume (r = 0.92, P < 0.05), whereas Vopt during sprint cycling was closely related to vastus lateralis MHC-II composition (r = 0.80, P < 0.05). CONCLUSIONS: These results provide further evidence of the importance of fast myosin isoform composition in the maintenance of dynamic muscle function in later life and particularly for maximal cycling performance.