Relation between preferred and optimal cadences during two hours of cycling in triathletes

Objectives

To determine whether the integrated electromyographic signal of two lower limb muscles indicates preferred cadence during a two hour cycling task.

Methods

Eight male triathletes performed right isometric maximum voluntary contraction (MVC) knee extension and plantar flexion before (P1) and after (P2) a two hour laboratory cycle at 65% of maximal aerobic power. Freely chosen cadence (FCC) was also determined, also at 65% of maximal aerobic power, from five randomised three minute sessions at 50, 65, 80, 95, and 110 rpm. The integrated electromyographic signal of the vastus lateralis and gastrocnemius lateralis muscles was recorded during MVC and the cycle task.

Results

The FCC decreased significantly (p<0.01) from P1 (87.4 rpm) to P2 (68.6 rpm), towards the energetically optimal cadence. The latter did not vary significantly during the cycle task. MVC of the vastus lateralis and gastrocnemius lateralis decreased significantly (p<0.01) between P1 and P2 (by 13.5% and 9.6% respectively). The results indicate that muscle activation at constant power was not minimised at specific cadences. Only the gastrocnemius lateralis muscle was affected by a two hour cycling task (especially at 95 and 110 rpm), whereas vastus lateralis remained stable.

Conclusion

The decrease in FCC observed at the end of the cycle task may be due to changes in the muscle fibre recruitment pattern with increasing exercise duration and cadence.     

Field measurements of oxygen uptake in elite orienteers during cross-country running using telemetry

Oxygen uptake (V_o2) was measured and economy calculated during running on a treadmill and during cross-country running in 14 male and 9 female orienteers using a telemetric system (K-2, Cosmed, Italy). The cross-country route comprised 3 parts: horizontal path running, horizontal running in light terrain and running in heavy terrain with obstacles and steep hills. Each subject accomplished the whole test route at a speed corresponding to 96±5% of maximal speed and at maximal speed. The running time at maximal speed was 19±3 min. The running economy was similar in treadmill and path running (211 ± 10 vs 210± 14 ml · kg⁻¹· km⁻¹), but V_o2 per km increased in light and heavy terrain to 290 ± 16 and 362±18 ml · kg⁻¹· km⁻¹, respectively. There was no difference in running economy between men and women. The elite group (5 men and 3 women) demonstrated 5% better running economy than the sub-elite (9 men and 6 women) during running in light and heavy terrain, whereas no difference was seen during treadmill and path running. In conclusion, elite orienteers have better running economy in light and heavy terrain than sub-elite orienteers.     

Longitudinal profiles of oxygen uptake during treadmill walking in able-bodied children: the locomotion energy and growth study

The purpose of this study was to document age-related changes in walking V_O2 in able-bodied boys and girls. Beginning at age 6 and ending at age 10, 23 children (14 girls, 9 boys) performed six 5-min bouts of level treadmill walking at 0.67, 0.89, 1.12, 1.34, 1.56, and 1.79 m s⁻¹ on an annual basis. Prior to data collection, subjects received 60 min of treadmill walking practice. During the last 2 min of each walking bout, a 2-min sample of expired air was collected in a meteorological balloon and analyzed to determine V_O2. Averaged across age, interindividual variation in V_O2 ranged from 32 to 41%. Repeated-measures analysis of variance demonstrated a speed by age interaction for V_O2, such that mean V_O2 rose (P≤0.05) across the five fastest speeds for 6-, 7-, 8-, and 10-year olds and increased over the entire speed range for 9-year olds. For all speeds, V_O2 decreased yearly from the ages of 6 to 8. When averaged across speeds, V_O2 was 27% higher for 6-year olds compared with 10-year olds. From a clinical perspective, access to longitudinal measurements of walking V_O2 in able-bodied children should be helpful in interpreting gait energy use in children with movement disorders and evaluating treatment strategies designed to reduce the aerobic demand of locomotion in youth with impaired mobility.     

湿润烧伤膏与中药内服治疗下肢静脉瘀血性溃疡疗效观察

目的：观察湿润烧伤膏(MEBO)外用，配合中药内服治疗下肢静脉瘀血性溃疡的疗效。方法：对42例不同原因所致下肢静脉瘀血性溃疡患者，均采用外涂MEBO暴露治疗；结合中药辨证分型治疗：湿热瘀阻型，以四妙勇安汤加味；气虚血瘀型，以丹参通脉汤和肾气丸加减，水煎，每日一剂，早、晚分两次服用。结果：42例病人治愈34例，好转6例，无效2例，总有效率95．3％。结论：湿润烧伤膏治疗下肢静脉瘀血性溃疡，能明显控制创面感染，改善局部血运，促进肉芽组织与皮肤再生，对血运障碍而致的顽固性溃疡疗效显著，明显优于传统疗法。     

尼卡地平与瑞芬太尼对老年鼻内镜手术患者控制性降压期间脑氧代谢的影响

目的探讨尼卡地平与瑞芬太尼在老年鼻内镜手术患者控制性降压应用时对脑氧代谢的影响。方法择期行老年鼻内镜手术患者46例,随机分为2组：尼卡地平组（N组）和瑞芬太尼组（R组）,每组23例。麻醉诱导后,2组进行控制性降压,N组采用尼卡地平、R组采用瑞芬太尼,分别记录麻醉诱导后(T0)、降压前即刻（T1）、降压后 15 min(T2)、降压后30 min(T3)、复压后15 min(T4)5个时点的心率（heart rate, HR)、动脉血压（mean arterial pressure, MAP)及脉氧饱和度（pulse oxygen saturation, SpO2）;抽取各时点外周动脉血及颈静脉血进行血气分析,并计算动脉血氧含量(arterial oxygen content, CaO2)、颈静脉血氧饱和度(jugular venous oxygen saturation, SjvO2)、静脉血氧含量(jugular veinoxygen content, CjvO2)、脑氧摄取率(cerebral extraction rate of oxygen, CERO2)。结果与T1时刻比较,T2、T3时刻2组MAP、SjvO2、CaO2、CERO2均明显降低(P<0.05),R组HR在T3时刻明显降低(P<0.05)、CjvO2增加(P<0.05);组间比较,2组HR、MAP、SpO2差异无统计学意义(P>0.05)。与R组比较,T2、T3时刻N组CjvO2、SjvO2水平明显升高（P<0.05）,而CERO2水平明显降低(P<0.05)。结论尼卡地平较瑞芬太尼用于控制性降压对心率影响更小,且脑氧代谢降低得更显著,对老年患者更加安全。     

Physical activity in the post-pubertal period is associated with maintenance of pre-pubertal high bone density-- a 5-year follow-up

OBJECTIVE: To evaluate the association between physical activity (PA) and skeletal growth in girls during adolescence. DESIGN: A 5-year, observational, population-based study (Reykjavik, Iceland). Subjects: Seventy-eight Caucasian girls, mean age 13.4+/-1.0 (mean+/-SD) years at baseline. METHODS: Bone mineral density (BMD, g/cm2) and bone width (cm) were measured in the forearm by single-photon absorptiometry at baseline and with dual-energy X-ray absorptiometry after 3 and 5 years, when lumbar spine, femoral neck (FN) and total body were also evaluated. Half of the physically active girls were compared with the other half of less active girls. RESULTS: BMD in physically active girls was higher in the forearm at both baseline (P=0.001) and after 5 years (P=0.04) in comparison with less active girls. BMD was higher for the total body (P=0.0001), spine L2-L4 (P=0.02) and FN (P=0.002) in the active girls at age 18. The accrual of forearm BMD and bone width from age 13 to 18 was no different when comparing the two groups. CONCLUSIONS: Pre-pubertal PA is associated with high BMD at age 13 and continued PA is associated with maintenance of high BMD until age 18.     

Loading of the knee during 3.0T MRI is associated with significantly increased medial meniscus extrusion in mild and moderate osteoarthritis

Purpose

Standard knee MRI is performed under unloading (ULC) conditions and not much is known about changes of the meniscus, ligaments or cartilage under loading conditions (LC). The aim is to study the influence of loading of different knee structures at 3 Tesla (T) in subjects with osteoarthritis (OA) and normal controls.

Materials and methods

30 subjects, 10 healthy and 20 with radiographic evidence of OA (10 mild and 10 moderate) underwent 3 T MRI under ULC and LC at 50% body weight. All images were analyzed by two musculoskeletal radiologists identifying and grading cartilage, meniscal, ligamentous abnormalities. The changes between ULC and LC were assessed. For meniscus, cartilage and ligaments the changes of lesions, signal and shape were evaluated. In addition, for the meniscus changes in extrusion were examined. A multivariate regression model was used for correlations to correct the data for the impact of age, gender, BMI. A paired T-Test was performed to calculate the differences in meniscus extrusion.

Results

Subjects with degenerative knee abnormalities demonstrated significantly increased meniscus extrusion under LC when compared to normal subjects (p = 0.0008–0.0027). Subjects with knee abnormalities and higher KL scores showed significantly more changes in lesion, signal and shape of the meniscus (80% (16/20) vs. 20% (2/10); p = 0.0025), ligaments and cartilage during LC.

Conclusion

The study demonstrates that axial loading has an effect on articular cartilage, ligament, and meniscus morphology, which is more significant in subjects with degenerative disease and may serve as an additional diagnostic tool for disease diagnosis and assessing progression in subjects with knee OA.