The effect of external loading upon power output in stair climbing

Summary Previous studies have examined man's ability to produce external power output during maximal repetitive work cycles of short duration. It appears, however, that there were methodological limitations which would inherently mask man's true capacities. Consequently, we examined the effect of variable external loads upon external power output as measured by running upstairs. Fourteen male subjects (16–31 years of age) who regularly participated in competitive sports performed maximal stair step tests under five experimental loading conditions (no external load, 10.1, 19.2, 24.2, and 29.2kg). Significant increases (P<0.05) in external power output were found. External power output increased from a mean of 15.9 W·kg^–1±1.0 (unloaded condition) to 18.5 W·kg^–1±1.5 (external load of 29.2 kg). This is the first modern investigation demonstrating that external loads effect external power output as measured by this technique.     

Clinical disability in posterior cruciate ligament deficient patients does not relate to knee laxity,but relates to dynamic knee function during stair descending

We investigated the factors which influence clinical subjective symptoms during activities in PCL deficient patients by evaluating knee laxity, muscle strength and knee mechanics during level walking, stair ascent and descent. Twenty-two subjects with isolated PCL deficient knees and 20 healthy volunteers were involved. The PCL deficient patients were divided into two subgroups based on previous history of experiencing giving-way during stair descent; a giving-way group (10 subjects) and a non giving-way group (12 subjects). Giving-way during activities of daily living is a key symptom in isolated PCL deficient patients. No statistically significant differences in the knee laxity, muscle strength and knee mechanics during level walking and were observed between the giving-way group and the non giving-way group. However, we found significant differences in the knee mechanics during stair ascent and descent between the two groups, and these differences were more remarkable during stair descent. Peak values of knee flexion angle, external knee flexion moment and posterior knee force during early stance phase were significantly lower in the giving-way group than in the non giving-way group. This study indicated that the symptom of giving-way during stair descent was related to knee mechanics during stair descent, unlike other quantitative evaluations such as KT-2000 or Biodex.     

T1 rho和T2 mapping序列观察运动对膝关节半月板的损伤

目的 采用T1 rho和T2 mapping序列观察步行、跑步和楼梯运动对膝关节半月板的影响。方法 对23名健康志愿者分别于30 min休息、走路、跑步和楼梯运动后行右膝关节3.0T MR扫描,每次运动随机选择,间隔期为1周,且运动前休息30 min,评估膝关节不同部位半月板运动后T1 rho值和T2值的变化。结果 运动后膝关节内侧半月板体部、后角及外侧半月板体部的T1 rho值和T2值均较休息状态减低（P均< 0.05）。膝关节内侧半月板T1 rho值和T2值在运动后较休息状态降低率后角 > 体部 > 前角,而外侧半月板体部 > 后角 > 前角。结论 T1 rho和T2 mapping成像是检测不同运动对膝关节半月板影响的敏感MRI技术。     

The use of a lateral wedge insole to reduce knee loading when ascending and descending stairs in medial knee osteoarthritis patients

Background

Stair climbing is a challenging task to the elderly being the task with the first complaint in patients with mild to moderate knee osteoarthritis. Stair climbing results in around six times more compressive load transmitted through the knee joint than walking on level ground. The purpose of this study was to assess whether lateral wedge insoles would reduce medial compartment knee loading when ascending and descending stairs in patients with medial knee osteoarthritis.

Methods

Eight patients with medial knee osteoarthritis were tested in random order with and without a pair of 5° off-the-shelf lateral wedge insoles for two separate activities (stair ascent and stair descent). Kinematic and kinetic data were collected for the lower extremity using a sixteen camera motion capture system and two force plates. Primary outcome measures were the external knee adduction moment and the knee adduction angular impulse.

Findings

During stair ascent and descent, lateral wedge insoles significantly (P < 0.05) reduced the 1st peak external knee adduction moment in early stance (ascent 6.8%, descent 8.4%), the trough in mid stance (ascent 13%, descent 10.7%), 2nd peak in the late stance (ascent 15%, descent 8.3%) and the knee adduction angular impulse compared to the control (standard shoe) with large effect sizes (0.75–0.95).

Interpretation

In this first study on stairs, lateral wedge insoles consistently reduced the overall magnitude of medial compartment loading during stair ascent and descent. Further research is needed to determine the relationship of this with clinical results when ascending and descending stairs with lateral wedge insoles.     

Biomechanical demands differentiate transitioning vs. continuous stair ascent gait in older women

Background

Stair ascent mechanics change with age, but little is known about the differing functional demands of transitioning and continuous ascent. Work investigating the risky transition from gait to ascent is sparse, and the strategies that older adults adopt to achieve these demanding tasks have not been investigated.

Methods

This study compared the biomechanics of a 2-step transitional (floor-to-step2) and continuous ascent cycle (step1-to-step3) and investigated the role of limb preference in relation to dynamometer-derived knee strength during this transition. A biomechanical analysis of 36 women (60–83 years) ascending a 3-step staircase was conducted.

Findings

The 2-step transitioning cycle was completed quicker, with a larger range of motion, increased forces, larger knee flexor and dorsiflexor moments and ankle powers (P ≤ 0.05), but reduced hip and knee flexion, smaller hip extensor moments and hip and knee powers compared to continuous ascent. During the transition, 44% of the participants demonstrated a consistent limb preference. In these cases large between-limb extensor strength differences existed (13.8%) and 71% of these participants utilised the stronger limb to execute the 2-step transitional cycle.

Interpretation

The preferential stronger-limb 2-step transitioning strategy conflicts with previous recommendations of a stronger lead limb for frail/asymmetric populations. Our findings suggest that most healthy older women with large between-limb differences utilise the stronger limb to achieve the considerable propulsion required to redirect momentum during the 2-step transition. The biomechanical demands of ascent, relative to limb strength, can inform exercise programmes by targeting specific muscle groups to help older adults maintain/improve general functioning.     

黑水缬草抗老年痴呆活性部位的研究

目的筛选黑水缬草抗老年痴呆的主要活性部位。方法利用腹腔注射半乳糖促老化与反复结扎双侧颈总动脉致脑缺血及大鼠侧脑室一次性注射Aβ1-40造成复合型老年痴呆大鼠模型。将Wistar大鼠随机分成8组:空白组、假损伤组、模型组、95%乙醇粗提物低剂量组、95%乙醇粗提物高剂量组、50%乙醇洗脱物低剂量组、50%乙醇洗脱物高剂量组、中药对照健脑胶囊组,各给药组于术后3d开始灌胃给药7d。采用Mor-ris水迷宫系统测试各组大鼠的学习记忆能力,并测定大鼠血浆中SOD、MDA和羟自由基的含量。结果黑水缬草95%乙醇粗提物低、高剂量组,50%乙醇洗脱物低、高剂量组,中药对照健脑胶囊组均可增强模型大鼠的学习记忆能力,SOD活力显著增加,MDA含量降低,抑制羟自由基能力增强,尤以50%乙醇洗脱物高剂量组效果最佳。结论50%乙醇洗脱物组分为黑水缬草抗老年痴呆的主要活性部位。