Stan Lindstedt

• Northern Arizona University

The body masses of extant mammals span over seven orders of magnitude. Within that size range there is extraordinary diversity of function, phylogenetic diversity that understandably presents fertile ground for uncovering biological insights. Remarkably transcending that diversity, are patterns that reveal body size-dependent constraints of “form a...

Since its belated discovery, our understanding of the giant protein titin has grown exponentially from its humble beginning as a sarcomeric scaffold to recent recognition of its critical mechanical and signaling functions in active muscle. One uniquely useful model to unravel titin's functions, muscular dystrophy with myositis (mdm), arose spontane...

The peculiar attributes of muscles that are stretched when active have been noted for nearly a century. Understandably, the focus of muscle physiology has been primarily on shortening and isometric contractions, as eloquently revealed by A.V. Hill and subsequently by his students. When the sliding filament theory was introduced by A.F. Huxley and H...

Introduction: Eccentric leg cycling (cycle ergometry adapted to impose muscle lengthening contractions) offers an effective exercise for restoring lower-body muscular function, maintaining health, and improving performance in clinical and athletic populations. Purpose: We extended this model to the upper body and evaluated the effectiveness of a...

When active muscles are stretched, our understanding of muscle function is stretched as well. Our understanding of the molecular mechanisms of concentric contraction has advanced considerably since the advent of the sliding filament theory, whereas mechanisms for increased force production during eccentric contraction are only now becoming clearer....

Although superthin filaments were inferred from early experiments on muscle, decades passed before their existence was accepted. Phylogenetic analyses suggest that titin, the largest known protein, first appeared in the common ancestor of chordates and nematodes and evolved rapidly via duplication. Twitchin and projectin evolved later by truncation...

The history of muscle physiology is a wonderful lesson in ‘the scientific method’; our functional hypotheses have been limited by our ability to decipher (observe) muscle structure. The simplistic understanding of how muscles work made a large leap with the remarkable insights of A. V. Hill, who related muscle force and power to shortening velocity...

Muscle produces force by forming cross bridges, using energy released from ATP. While the magnitude and duration of force production primarily determine the energy requirement, nearly a century ago Fenn observed that muscle shortening or lengthening influenced energetic cost of contraction. When work is done by the muscle, the energy cost is increa...

As we approach the centenary of the term comparative physiology, we re-examine its role in modern biology. Finding inspiration in Krogh's classic 1929 paper, we first look back to some timeless contributions to the field. The obvious and fascinating variation among animals is much more evident than is their shared physiological unity, which transce...

Shivering frequency scales predictably with body mass and is ten times higher in a mouse than a moose. The link between shivering frequency and body mass may lie in the tuning of muscle elastic properties. Titin functions as a muscle "spring," so shivering frequency may be linked to titin's structure. The muscular dystrophy with myositis (mdm) mous...

![Figure][1] Stan Lindstedt discusses August Krogh's classic paper ‘The progress of physiology’, published in the American Journal of Physiology in 1929. August Krogh wrote an essay that appeared in the American Journal of Physiology in 1929. In this essay he introduces an experimental

This laboratory exercise demonstrates fundamental principles of mammalian locomotion. It provides opportunities to interrogate aspects of locomotion from biomechanics to energetics to body size scaling. It has the added benefit of having results with robust signal to noise so that students will have success even if not "meticulous" in attention to...

This non-exhaustive, mini review reports on the application of eccentric exercise in various rehabilitation populations. The two defining properties of eccentric muscle contractions, a potential for high muscle force production at an energy cost that is uniquely low, are revisited and formatted as exercise countermeasures to muscle atrophy, weaknes...

Comparative physiology often provides unique insights in animal structure and function. It is specifically through this lens that we discuss the fundamental properties of skeletal muscle and animal locomotion, incorporating variation in body size and evolved difference among species. For example, muscle frequencies in vivo are highly constrained by...

Motor control comprises not only descending input from the nervous system and proprioceptive feedback, but also muscle viscoelastic properties, body dynamics, and interactions with the environment. Proprioceptive sense organs and spinal reflexes regulate muscle stiffness dynamically during perturbations. In addition to these slower acting reflexes,...

MONROY, J.A., K.L. POWERS, L.A. GILMORE, T.A. UYENO, S.L. LINDSTEDT, and K.C. NISHIKAWA. What is the role of titin in active muscle? Exerc. Sport Sci. Rev., Vol. 40, No. 2, pp. 73-78, 2012. Several properties of muscle defy explanation solely based on the sliding filament-swinging cross-bridge theory. Indeed, muscle behaves as though there is a dyn...

Recent studies have demonstrated a role for the elastic protein titin in active muscle, but the mechanisms by which titin plays this role remain to be elucidated. In active muscle, Ca(2+)-binding has been shown to increase titin stiffness, but the observed increase is too small to explain the increased stiffness of parallel elastic elements upon mu...

Skeletal muscle is a dynamic tissue that responds adaptively to both the nature and intensity of muscle use. This phenotypic plasticity ensures that muscle structure is linked to patterns of muscle use throughout the lifetime of an animal. The cascade of events that result in muscle restructuring - for example, in response to resistance exercise tr...

The sections in this article are: An Integrative and Absolute Approach to Adaptation and Design Caveats and Potential Limitations of the Approach Science and Semantics of Adaptation and Design Organization of the Chapter Components of the Mechanical System Molecular Level Cellular Level Organ Level/Anatomical Level Design Constraints of th...

The purpose of this study was to describe an electromyogram (EMG) pattern during a submaximal eccentric task in 7 subjects adapted to high-force chronic eccentric exercise and 6 subjects naive to eccentric exercise. The EMG in all subjects was quantified during identical submaximal (200 W) eccentric and concentric cycle ergometry tasks. The EMG of...

Background and Purpose:: Elderly individuals participate in resistance exercise to induce an anabolic response and grow muscle to help overcome functional deficits. It is thought that a muscle damage and inflammatory response to resistance exercise is a necessary prerequisite for an anabolic and muscle growth response. Methods:: This is a descripti...

We investigated the capacity for phenotypic plasticity of skeletal muscle from Varanus exanthematicus, the savannah monitor lizard. Iliofibularis muscle from one leg of each lizard was electrically stimulated for 8 weeks. Both stimulated and contralateral control muscles were collected and processed for electron microscopy. We used stereological an...

Elderly individuals participate in resistance exercise to induce an anabolic response and grow muscle to help overcome functional deficits. It is thought that a muscle damage and inflammatory response to resistance exercise is a necessary prerequisite for an anabolic and muscle growth response. This is a descriptive study of 11 elderly individuals...

Monodelphis domestica (Didelphidae: Marsupialia) lacks brown adipose tissue and thus relies on skeletal muscle as its primary thermogenic organ. Following cold exposure, the aerobic capacity of skeletal muscle in these animals is greatly increased. We investigated the effects of this plastic response to thermogenesis on locomotion and muscle mechan...

Marsupials lack brown adipose tissue, and therefore rely exclusively on other tissues for thermogenesis. To determine the magnitude of phenotypic plasticity of the liver in response to changing metabolic demand, gray short-tailed opossums (M. domestica) were exposed to thermoneutral (28 degrees C) or cold (9-12 degrees C) conditions continuously fo...

Monodelphis domestica (Marsupialia: Didelphidae) was used as a model animal to investigate and compare muscle adaptation to exercise training and cold exposure. The experimental treatment consisted of four groups of animals: either warm or cold acclimation temperature and with or without endurance exercise training. Maximal aerobic capacity during...

Muscles operate eccentrically to either dissipate energy for decelerating the body or to store elastic recoil energy in preparation for a shortening (concentric) contraction. The muscle forces produced during this lengthening behavior can be extremely high, despite the requisite low energetic cost. Traditionally, these high-force eccentric contract...

The objective of this study was to determine if a chronic eccentric training intervention, i.e., negative work, could limit or even reverse sarcopenia and its related impairments and functional limitations. Is high-force eccentric training tolerable by elderly people and will it result in improved muscle size, strength, balance, and fall risk? 21 f...

Reducing the cost of high-frequency muscle contractions can be accomplished by minimizing cross-bridge cycling or by recycling elastic strain energy. Energy saving by contractile minimization has very different implications for muscle strain and activation patterns than by elastic recoil. Minimal cross-bridge cycling will be reflected in minimal co...

Many mechanisms reduce the cost of muscle activity. Here, we describe a set of specializations that reduce the cost of contraction in the high-frequency twitches that are used by a wide variety of animals for either sound production or flight. Minimizing the cost of these contractions means that cellular ATP production can meet ATP demand and susta...

During normal animal movements, the forces produced by the locomotor muscles may be greater than, equal to or less than the forces acting on those muscles, the consequences of which significantly affect both the maximum force produced and the energy consumed by the muscles. Lengthening (eccentric) contractions result in the greatest muscle forces a...

An abstract is unavailable. This article is available as HTML full text and PDF.

One challenge for veterinarians, animal facilities and research scientists is the making of physiological estimates appropriate to a variety of species for which data are often either completely lacking or are incomplete. Our intent in compiling the data in this paper is to provide the best possible database of normal physiological and anatomical v...

When the force applied to a muscle exceeds the force produced by the muscle it will lengthen, absorbing mechanical energy. These eccentric contractions, which result in both braking and storing elastic recoil energy in normal locomotion, require very little metabolic energy, yet they are characterized by high force production.

Human endurance performance is often evaluated on the basis of the maximal rate of oxygen uptake during exercise (V(O(2)max)). Methods for overcoming limits to V(O(2)max) are touted as means for increasing athletic endurance performance. Here, we argue that the respiratory system is well designed for delivering O(2) to meet O(2) demands and that no...

no abstract available

Substantial ATP supply by glycolysis is thought to reflect cellular anoxia in vertebrate muscle. An alternative hypothesis is that the lactate generated during contraction reflects sustained glycolytic ATP supply under well-oxygenated conditions. We distinguished these hypotheses by comparing intracellular glycolysis during anoxia to lactate efflux...

We inadvertently subjected a group of goats to 5 mo of cold exposure (mean minimum temperature less than -13 degrees C) during an experiment designed to examine the effects of training by daily running on one member of each sibling pair. During the three coldest months, the sedentary but cold-exposed goats experienced a 34% increase in maximal oxyg...

We inadvertently subjected a group of goats to 5 mo of cold exposure (mean minimum temperature less than -13 degreesC) during an experiment designed to examine the effects of training by daily running on one member of each sibling pair. During the three coldest months, the sedentary but cold-exposed goats experienced a 34% increase in maximal oxyge...

During locomotion, major muscle groups are often activated cyclically. This alternate stretch-shorten pattern of activity could enable muscle to function as a spring, storing and recovering elastic recoil potential energy. Because the ability to store and recover elastic recoil energy could profoundly affect the energetics of locomotion, one might...

Lengthening (eccentric) muscle contractions are characterized by several unusual properties that may result in unique skeletal muscle adaptations. In particular, high forces are produced with very little energy demand. Eccentrically trained muscles gain strength, but the specific nature of fiber size and composition is poorly known. This study asse...

Eccentric contractions, the lengthening of muscle while producing force, are a common part of our everyday movements. This study presents a challenge to the accepted notion that eccentric work causes obligatory muscle injury while demonstrating that an increase in muscle strength, via eccentric work, can occur with little demand for oxygen. Nine he...

Vertebrate sound-producing muscles can contract at frequencies greater than 100 Hz, a feat impossible in locomotory muscles. This is not accomplished by unique proteins or structures but by qualitative shifts in isoforms and quantitative reapportionment of structures. Speed comes with costs and trade-offs, however, that restrict how a muscle can be...

Skeletal muscle fibers are composed of three structural elements, each contributing a unique aspect of muscle function, yet each 'competing' in a sense for space inside the cell. The volume occupied by myofibrils determines the force of contraction, the volume of sarcoplasmic reticulum sets the rate of onset and relaxation of a fiber's contraction...

At the highest altitude, aerobic work is limited by environmental oxygen availability. We therefore reasoned that the hyperpnea associated with endurance training at altitude should provide a strong stimulus for adaptation of the ventilatory muscles. We measured peak inspiratory muscle pressure-flow characteristics (inspiring through graded resisto...

Sound production is one of the most energetically costly activities in animals. Minimizing contraction costs is one means of achieving the activation rates necessary for sound production (20-550 Hz) (refs 1-3) without exceeding energy supplies. Rattlesnakes produce a sustained, high-frequency warning sound by extremely rapid contraction of their ta...

Vertebrate sound producing muscles often operate at frequencies exceeding 100 Hz, making them the fastest vertebrate muscles. Like other vertebrate muscle, these sonic muscles are "synchronous," necessitating that calcium be released and resequestered by the sarcoplasmic reticulum during each contraction cycle. Thus to operate at such high frequenc...

The western diamondback rattlesnake Crotalus atrox can rattle its tail continuously for hours at frequencies approaching 90 Hz. We examined the basis of these fast sustainable contractions using electromyography, data on oxygen uptake and the quantitative ultrastructure of the tailshaker muscle complex. The tailshaker muscle has no apparent unique...

One source of muscle fatigue may be the failure to provide the required oxygen by any step in the oxygen transport cascade or a lack of the necessary machinery to utilize that oxygen. We favor abandoning the concept of a single rate-limiting step for the concept of tuned resistors, each contributing to the overall resistance to oxygen flow. However...

The mean minimal transit time for blood in muscle capillaries (tc) was estimated in six species, spanning two orders of magnitude in body mass and aerobic capacity: horse, steer, dog, goat, fox and agouti. Arterial (CaO2) and mixed venous (CvO2) blood O2 concentrations, blood hemoglobin concentrations ([Hb]) and oxygen uptake rates were measured wh...

We have examined aerobic exercise performance among the mammals with particular attention to the constraints that body size places on all aspects of muscle biomechanics, aerobic energetics, tissue oxygen diffusion, cardiovascular oxygen delivery, and pulmonary oxygen uptake. Several body-size-dependent patterns emerge that seemingly govern aerobic...

Symmorphosis predicts that animal design is optimized in such a way that structure ‘satisfies but does not exceed’ functional requirements. To provide one test of this hypothesis, we examined peak inspiratory flow and its relation to maximum oxygen uptake in humans. We measured maximal forced (peak) inspiratory flow (V̇imax) and maximum oxygen upta...

Body size fundamentally affects maximal locomotor performance in mammals. Comparisons of performances of different-sized animals yield different results if made using relative, rather than absolute scales. Absolute speed may be a reasonable way to evaluate the locomotor performance of an animal that must escape predators in real time. However, comp...

The mean minimal capillary transit time was estimated in muscles of various animals using a combination of physiological and morphometric methods. Radioactive microspheres were injected intravascularly in various animals running on a treadmill at maximum oxygen consumption rate (VO2,max) to label blood flow to individual muscles. The muscles were t...

The pronghorn antelope (Antilocapra americana) has an alleged top speed of 100 km h-1, second only to the cheetah (Acionyx jubatus) among land vertebrates, a possible response to predation in the exposed habitat of the North American prairie. Unlike cheetahs, however, pronghorn antelope are distance runners rather than sprinters, and can run 11 km...

The relationship between maximal oxygen consumption rate (VO2max) and mitochondrial content of skeletal muscles was examined in horses and steers (n = 3 each). Samples of the heart left ventricle, diaphragm, m. vastus medialis, m. semitendinosus, m. cutaneous thoracicus and m. masseter, as well as samples of muscles collected in a whole-body sampli...

Sex ratios significantly different from 1:1 usually are observed in trap captures of mustelids, consistently skewed toward males. This apparent sampling bias generally has been attributed to sexual dimorphism of home-range sizes in mustelids, postulated to result in greater exposure of males to traps. Small mustelids exhibit more strongly skewed se...

In this paper we have explored the linked series of structures that collectively comprise the respiratory system. In examining each of these structural resistors, some seem to be primarily fixed, for example, the trachea, while others must be primarily variable or adaptable, for example, the cardiovascular system. Those structures that are truly va...

At an animal's maximum aerobic capacity (VO2max), the O2 flowing through the respiratory system is consumed by a functionally exclusive sink, skeletal muscle mitochondria. Thus, O2 consumption will never exceed the muscles O2 demand. If the system is ideally designed, structures upstream to the skeletal muscle O2 sink must be built to insure adequa...

We consider the distribution of scientific ages of professors in ten astronomy departments in the United States and find that the average astronomer is growing older at a rate of about 6 months per year at present. This aging will continue through the end of the 1990s, at which time we predict that the average professorial astronomer will be around...

The relationship between home range area and body size of terrestrial mammals is reconsidered in light of the concept of biological time. Biological time is an internal, body-mass-dependent, time scale to which the durations (of rates) of biological events are entrained. These events range from purely physiological (e.g., muscle contraction time) t...

All skeletal muscle can produce roughly the same maximal cross-sectional force; however, the power (energy X time-1) required to develop and maintain that force increases with increasing contraction velocity. Thus the rate of muscle tension development may be of primary importance in setting the energy demand of contracting muscle. We have estimate...

The concept of adaptation has long been a central idea in the study of the survival and evolution of life on earth (e.g., Williams, 1966). The potential existence of biological adaptation is best thought of as a hypothesis to be tested or an idea to be approached, and not a phenomenon that is automatically inherent in each and every characteristic...

The adaptation of muscle structure, power output, and mass-specific rate of maximal O2 consumption (VO2max/Mb) with endurance training on bicycle ergometers was studied for five male and five female subjects. Biopsies of vastus lateralis muscle and VO2max determinations were made at the start and end of 6 wk of training. The power output maintained...

One can predict fasting endurance in mammals by dividing energy reserves by their rate of use. The result, the scaling of fasting endurance, favors large body size. This relationship is of primary significance in seasonal environments where organisms must endure occasional periods of fasting.-from Authors

The quantitative structural composition of skeletal muscle tissue shows a wide range of variability among different species of animals and in any one species among muscles with a different function. Moreover, experimental manipulations such as exercise training or chronic electrical stimulation can dramatically change the ultrastructural appearance...

Allometry is used as a tool to explain the apparent mismatch of oxygen consumption and diffusing capacity in the mammalian lung. By combining equations for pulmonary capillary volume and cardiac output, it is apparent that erythrocyte transit time through the lung must scale disproportionately to body mass. This inequality is a consequence of physi...

The heart mass was measured and the volume density of mitochondria, Vv(mt,f), morphometrically estimated in 11 mammalian species ranging from shrew (3 g) to cattle (920 kg). The mass or the volume of the heart muscle (Vh) was found to scale as Mb0.970 whereas Vv(mt,f) scaled as Mb−0.044. Hence, the total volume of mitochondria in heart, V(mt), scal...

In European woodmice the amount and intensity of daily activity was compared to oxygen uptake and to the potential for oxidative metabolism of heart and skeletal muscle. One group of animals was inactivated by exposition to light during night time; another group of animals was trained by enforced running on a treadmill. The oxidative potential of t...

Since O2 is mainly consumed in muscle mitochondria during heavy physical work, one would expect to find a relationship between the volume density of mitochondria in skeletal muscles and maximal O2 uptake. We analyzed the volume density of mitochondria, Vv(mt,f) in four muscles of a series of African mammals ranging in body mass from 0.4 to 251 kg....

The relationship between capillary density and mitochondrial volume density in skeletal muscle tissue is investigated on 25 African mammals ranging in body mass from 0.4 to 251 kg. As a general trend higher capillary densities, NA (c,f) are found in muscles with higher volume densities of mitochondria, Vv(mt,f). The individual data however show con...

The Concept of physiological time is extended from contributions of Adolph, Hill, and Stahl to included a wider range of events in the life histories of mammals and birds. The durations of physiological, developmental, and ecological cycles show nearly parallel exponential relationships to body size (masss1/4). Maximum life span approximates a fixe...

Desert shrews (Notiosorex crawfordi; 4 g) enter into daily bouts of very shallow torpor, when restricted in their food intake. These bouts, though interrupted and uneven, last throughout that portion of the day the animals' cages are lighted. Body temperature is apparently regulated by fine adjustments of metabolic heat production in hypothermic as...

The physiological and ecological coupling of the desert shrew (Notiosorex crawfordi) to its environment has been examined. Mean standard metabolism between 32 and 36 C equaled 17.12 W·kg⁻¹. Below 32 C metabolic rate increased linearly to a high of 79 W·kg⁻¹ at 10 C. The heat transfer coefficient was 3.05 W·kg⁻¹ · C⁻¹ below 32 C. At 37 C air tempera...

The renal morphology of three species of desert dwelling Perognathus rodents were compared to Dipodomys and two species of sympatric cricetid rodents. Perognathus has a highly adapted unipolar kidney capable of urine concentration up to 7,500 mOsm/KgH2O. Two major modifications were observed in these kidneys. (1) There is elongation of both the inn...