The Evolution of the Functional Role of Trunk Muscles During Locomotion in Adult Amphibians

SYNOPSIS. The axial musculature of all vertebrates consistsof two principal masses, the epaxial and hypaxial muscles. Theprimitive function of both axial muscle masses is to generatelateral bending of the trunk during swimming, as is seen inmost fishes. Within amphibians we see multiple functional andmorphological elaborations of the axial musculature. These elaborationsappear to be associated not only with movement into terrestrialhabits (salamanders), but also with subsequent locomotor specializationsof two of the three major extant amphibian clades (frogs andcaecilians). Salamanders use both epaxial and hypaxial musclesto produce lateral bending during swimming and terrestrial,quadrupedal locomotion. However during terrestrial locomotionthe hypaxial muscles are thought to perform an added function,resisting long-axis torsion of the trunk. Relative to salamanders,frogs have elaborate epaxial muscles, which function to bothstabilize and extend the iliosacral and coccygeosacral joints.These actions are important in the effective use of the hindlimbsduring terrestrial saltation and swimming. In contrast, caecilianshave relatively elaborate hypaxial musculature that is linkedto a helix of connective tissue embedded in the skin. The helixand associated hypaxial muscles form a hydrostatic skeletonaround the viscera that is continuously used to maintain bodyposture and also contributes to forward force production duringburrowing.     

The Seasonal Acclimatisation of Locomotion in a Terrestrial Reptile,Plestiodon chinensis （Scincidae）

Studies of the seasonal acclimatisation of behavioural and physiological processes usually focus on aquatic or semi-aquatic ectotherms and focus less effort on terrestrial ectotherms that experience more thermally heterogeneous environments. We conducted comparative studies and thermal acclimation experiments on the locomotion of the Chinese skink （Plestiodon chinensis） to test whether seasonal acclimatisation in locomotion exists in these terrestrial ectothermic vertebrates, and whether seasonal acclimatisation is predominantly induced by thermal environments. In natural populations, skinks ran faster during the summer season than during the spring season at high-test temperatures ranging from 27℃ to 36℃ but not at low-test temperatures ranging from 18℃ to 24℃. In contrast, the thermal acclimation experiments showed that the cold-acclimated skinks ran faster than the warm-acclimated skinks at the low- test temperatures but not at high-test temperatures. Therefore, the seasonal acclimatisation occurs to P chinensis, and may be induced by temperature as well as other factors like food availability, as indicated by the seasonal variation in the thermal dependence of locomotion, and the discrepancy between seasonal acclimatisation and thermal acclimation on locomotion.     

Evidence for a Mass Dependent Step-Change in the Scaling of Efficiency in Terrestrial Locomotion

A reanalysis of existing data suggests that the established tenet of increasing efficiency of transport with body size in terrestrial locomotion requires re-evaluation. Here, the statistical model that described the data best indicated a dichotomy between the data for small (<1 kg) and large animals (>1 kg). Within and between these two size groups there was no detectable difference in the scaling exponents (slopes) relating metabolic (E _met) and mechanical costs (E _{mech, CM}) of locomotion to body mass (M _b). Therefore, no scaling of efficiency (E _{mech, CM}/E _met) with M _b was evident within each size group. Small animals, however, appeared to be generally less efficient than larger animals (7% and 26% respectively). Consequently, it is possible that the relationship between efficiency and M _b is not continuous, but, rather, involves a step-change. This step-change in the efficiency of locomotion mirrors previous findings suggesting a postural cause for an apparent size dichotomy in the relationship between E _met and M _b. Currently data for E _{mech, CM} is lacking, but the relationship between efficiency in terrestrial locomotion and M _b is likely to be determined by posture and kinematics rather than body size alone. Hence, scaling of efficiency is likely to be more complex than a simple linear relationship across body sizes. A homogenous study of the mechanical cost of terrestrial locomotion across a broad range of species, body sizes, and importantly locomotor postures is a priority for future research.     

Anuran Locomotion: Ontogeny and Morphological Variation of a Distinctive Set of Muscles

Adult morphological variation of muscles originating on the iliac shaft (M. iliacus externus, M. internus, and tensor fasciae latae) and vertebrae (M. longissimus dorsi, M. coccygeosacralis, and M. coccygeoiliacus) that are involved in postmetamorphic anuran locomotion was recorded in 41 neobatrachians and coded in 13 more based on the literature, for a total of 54 anuran species. In addition, we explored the spatial and temporal sequences in the ontogeny of these set of muscles from larval series of 19 neobatrachians whose adults differ in locomotion and lifestyle. Our findings suggest that: (1) jumping, swimming, and/or walking are capabilities that could have been achieved from novelties of limbs and protractor muscles of the femur rather than from changes in the axial musculoskeletal system; (2) the initial ontogenetic phase of the locomotion comprises the capability to escape, when the tail is still present; (3) the secondary phase of locomotion comprises changes in the axial skeleton and muscles integrated to the pelvis and might develop simultaneously with the new feeding mechanism of the recently metamorphosed frog.     

Terrestrial Intermittent Exercise: Common Issues for Human Athletics and Comparative Animal Locomotion

The earliest studies of intermittent exercise physiology notedthat moving intermittently (i.e., alternating brief movementswith brief pauses) could transform a heavy workload into a submaximalone that can be tolerated and sustained. The brief pauses thatcharacterize intermittent locomotion permit at least partialrecovery from prior activity. This research provided the foundationfor the development of interval training and more recently forthe re-evaluation of steady-state paradigms for comparativeanimal locomotion. In this paper I review key concepts underlyingthe performance of repeated activity. I provide examples fromhuman athletics and training and comparative animal locomotion.To explore the limits of intermittent exercise performance,I examine the performance limits for continuous exercise andthe rate and extent of the recovery of performance capacityfollowing activity. While it is evident that altering locomotorbehavior (i.e., moving intermittently) can alter the capacityof an animal to perform work, mathematical models of intermittentexercise could predict strategies (i.e., exercise intensity,exercise duration, and pause duration) that will increase performancelimits for intermittent activity.     

The Roles of Calcium in Excitation-Contraction Coupling in Various Muscles of the Frog, Mouse, and Barnacle

In rectus abdominis muscles of the frog the active shorteningprovoked by 15–40 mM K was supported by Ca, Sr, and Ba,but not by Ni, Co, Mn, Cd, or Zn ions. Addition of the lattercations to a solution containing Ca decreased the responsesin a manner suggesting competitive inhibition. The shorteningof the rectus muscle found in divalent cation-free, low K solutionsis abolished by Ni, Co, Mn, and Mg. In rat muscles a transientincrease in the contractural responses to elevated potassiumwas observed when Ni was applied following partial washout ofCa. In single muscle fibers of the barnacle, development oftension was supported by Ca and Sr, and the other divalent cationswere without effect. Retention of Ca⁴⁵ in barnacle resting musclefibers soaked in solutions containing 10 mM Ca for 2 min andsubsequently washed for 10 min was 60 ± 3.1 mµMCa/g, whereas retention of Ca⁴⁵ in contracting muscles similarlyexposed to Ca⁴⁵ was 156 + 17 mµM Ca/g of fresh muscle.The results are compatible with the idea that activation ofcontraction in some types of muscles is due to entry of extracellularCa.     

Anatomical Cross-Sectional Areas and Volumes of the Muscles of the Lower Extremities

The maximum anatomical muscle cross-sectional areas and volumes of the muscles in the lower part of the body, thigh, and shank were measured by magnetic resonance imaging. The largest cross-sectional areas were 145.65 and 63 cm² in m. gluteus maximus and m. vastus, respectively, referred to as mm. adductors. In the thigh, m. vastus had the largest volume, 1505 ± 271 cm³, and in the shank, m. soleus had the largest volume, 552 ± 64 cm³. Close correlations (0.50 < R < 0.75) between the maximum areas of the lower extremity muscles were evidence for a certain relationship between the muscle cross-sections. A multiple regression equation was formulated to calculate the maximum anatomical cross-sectional areas and volumes in the muscles of the lower extremities with respect to some anthropometric parameters.     

Influence of Stretching Training of the Lower Limbs on Postural Stability

Human Physiology - The paper investigates the effects of stretching training on stabilographic and kinematic parameters of one-legged posture stability in healthy girls (n = 14). Stretching...     

帕瑞昔布钠用于下肢手术术后镇痛的安全性及其对阿片类药物用量的节俭作用

目的:探讨帕瑞昔布钠用于下肢手术术后镇痛的疗效、安全性及其对阿片类药物用量的节俭作用.方法:随机、双盲、安慰剂对照、平行分组研究,18-60岁、ASA Ⅰ或Ⅱ级、择期硬膜外腔阻滞下下肢手术病人,手术结束时,随机静脉注射帕瑞昔布钠40mg或生理盐水5ml,12h后再静脉注射帕瑞昔布钠40 mg或生理盐水5 ml,同时采用芬太尼进行病人自控静脉镇痛.观察术后2,4,8,12和24h的疼痛强度(VAS评分)、给药前后的生命体征、不良反应和生化检查指标、术后芬太尼用量、病人自控镇痛(PCA)有效次数.结果:共完成220例,其中采用帕瑞昔布钠116例,安慰剂104例.与安慰剂组相比,帕瑞昔布钠组术后2,4,8,12和24h VAS评分降低(P＜0.05),而有关不良反应和检查结果异常发生率的差异无统计学意义(P＞0.05),术后12h和24 h芬太尼用量明显减少(P＜0.05),术后12h和24hPCA有效次数降低(P＜0.05).结论:下肢手术后静脉给予帕瑞昔布钠40mg bid,镇痛效果佳,安全可靠,明显减少了术后芬太尼用量,提高病人术后镇痛质量.     

Relative Roles of the Ankle and Hip Muscles in Human Postural Control in the Frontal Plane during Standing

The main goal was to evaluate the relative roles of the ankle and hip muscles in human postural control in the frontal plane during normal upright standing. Experiments were designed to compare upright standing with and without the involvement of the ankle joint. The results demonstrated that standing balance in the frontal plane depended largely on the hip muscles and just slightly on the ankle muscles, which performed only small adjusting movements in the frontal plane. During quiet standing, the human body swayed in the frontal plane as a two-component inverted pendulum or, when no ankle joint torque was permitted, as an inverted pendulum consisting of only one component.     

Convergence in Reflex Pathways from Multiple Cutaneous Nerves Innervating the Foot Depends upon the Number of Rhythmically Active Limbs during Locomotion

Neural output from the locomotor system for each arm and leg influences the spinal motoneuronal pools directly and indirectly through interneuronal (IN) reflex networks. While well documented in other species, less is known about the functions and features of convergence in common IN reflex system from cutaneous afferents innervating different foot regions during remote arm and leg movement in humans. The purpose of the present study was to use spatial facilitation to examine possible convergence in common reflex pathways during rhythmic locomotor limb movements. Cutaneous reflexes were evoked in ipsilateral tibialis anterior muscle by stimulating (in random order) the sural nerve (SUR), the distal tibial nerve (TIB), and combined simultaneous stimulation of both nerves (TIB&SUR). Reflexes were evoked while participants performed rhythmic stepping and arm swinging movement with both arms and the leg contralateral to stimulation (ARM&LEG), with just arm movement (ARM) and with just contralateral leg movement (LEG). Stimulation intensities were just below threshold for evoking early latency (<80 ms to peak) reflexes. For each stimulus condition, rectified EMG signals were averaged while participants held static contractions in the stationary (stimulated) leg. During ARM&LEG movement, amplitudes of cutaneous reflexes evoked by combined TIB&SUR stimulation were significantly larger than simple mathematical summation of the amplitudes evoked by SUR or TIB alone. Interestingly, this extra facilitation seen during combined nerve stimulation was significantly reduced when performing ARM or LEG compared to ARM&LEG. We conclude that locomotor rhythmic limb movement induces excitation of common IN reflex pathways from cutaneous afferents innervating different foot regions. Importantly, activity in this pathway is most facilitated during ARM&LEG movement. These results suggest that transmission in IN reflex pathways is weighted according to the number of limbs directly engaged in human locomotor activity and underscores the importance of arm swing to support neuronal excitability in leg muscles.