在负荷状态下肌肉等长、等张收缩声谱特征的研究

根据肌肉收缩滑动学说,当肌肉收缩时,肌纤维间产生滑动摩擦。那么肌纤维相互滑动运动是否产生肌声,肌声与负载量、运动状态、速度等方面存在何种关系已引起关注。作者用声学法研究肱二头肌在负荷下等长、等张收缩、揭示其发声规律。     

The efficacy of cooling with phase change material for the treatment of exercise-induced muscle damage: pilot study

Post-exercise cryotherapy treatments are typically short duration interventions. This study examined the efficacy of prolonged cooling using phase change material (PCM) on strength loss and pain after eccentric exercise. Eight adults performed 120 bilateral eccentric quadriceps contractions (90% MVC). Immediately afterwards, frozen PCM packs (15°C) were placed over the quadriceps, with room temperature PCM packs on the contralateral quadriceps. Skin temperature was recorded continually (6 h PCM application). Isometric quadriceps strength and soreness were assessed before, 24, 48, 72 and 96 h post-exercise. The protocol was repeated 5 months later, with room temperature PCM applied to both legs. There were three treatments: legs treated with 15°C PCM packs (direct cooling), legs treated with room temperature PCM packs contralateral to the 15°C PCM packs (systemic cooling), and legs tested 5 months later both treated with room temperature PCM packs (control). Skin temperature was 9°C–10°C lower with direct cooling versus systemic cooling and control (P < 0.01). Strength loss and soreness were less (P < 0.05) with direct cooling versus systemic cooling and control (strength 101%, 94%, 93%, respectively; pain 1.0, 2.3, 2.7, respectively). Six hours of PCM cooling was well tolerated and reduced strength loss and pain after damaging exercise.     

The effects of chronic exercise training status on motor unit activation and deactivation control strategies

This study examined the mechanomyographic (MMG_RMS) amplitude–force relationships for 5 (age = 19.20 ± 0.45 years) aerobically trained (AT), 5 (age = 25 ± 4.53 years) resistance-trained (RT) and 5 (age = 21.20 ± 2.17 years) sedentary (SED) individuals. Participants performed an isometric trapezoidal muscle action at 60% maximal voluntary contraction of the leg extensors that included linearly increasing, steady force, and linearly decreasing muscle actions. MMG and skinfold thickness were recorded from the vastus lateralis. b and a terms were calculated from the natural log-transformed MMG_RMS–force relationships (linearly increasing and decreasing segments) for each participant. An average of MMG_RMS was calculated for the entire steady force segment. The b terms for the RT (0.727 ± 0.334) and SED (0.622 ± 0.281) were significantly greater (P < 0.05) than the AT (0.159 ± 0.223) and were greater during the linearly increasing (0.622 ± 0.426) than decreasing (0.383 ± 0.269) segments when collapsed across segments and training status, respectively. MMG_RMS during the steady force segment and skinfold thicknesses were not different among training statuses (P = 0.106, P = 0.142). Motor unit (MU) activation strategies were influenced as a function of exercise training status and muscle action. Future research is needed to fully understand the implications of these changes in MU control strategies as a result of chronic exercise training on exercise and athletic performance.     

减量训练对大鼠骨骼肌最大等长收缩力的影响

为探讨减量训练对骨骼肌最大等长收缩力的影响.将成年S.D雄性大鼠随机分为2组,正常对照组（NC,16只）和快速力量训练组（PT,Power training,36只）.快速力量训练6周后,PT组又分为训练对照组（PTC,12只）、减量训练1组（PTT1,12只）和减量训练2组（PTT2,12只）.PTC组继续进行原训练,PTT1组和PTT2组进行6周减量训练.最后测定大鼠右侧后腿腓肠肌最大等长收缩力相对值（F/m）,观察减量训练对其的影响.结果表明,80%强度的减量训练后最大等长收缩力相对值呈先下降后回升直至超量恢复的趋势;50%强度的减量训练后相对值呈持续下降趋势,没有再回升.适当的减量训练可以巩固和加强训练效果;减量过多则会导致训练效果丧失,出现减量后的不良影响.