A Criticism Of Metabolic Cost

A game of touch requires the use of all energy systems at once but in varied amounts. The body will automatically choose which energy system it requires the most based on the fitness components used. It has been identified above that the three main components used by a middle are; Aerobic capacity, muscular endurance and coordination. In figure 12.5 it shows the relationship between components of fitness and energy systems. Both aerobic capacity and muscular endurance relate to the Aerobic system. The aerobic system uses oxygen and is generally one of low-mid intensity and/or of a longer duration. Middles utilise this energy system because they continuously require energy production at an almost equal rate.

Dr. Delp’s research analyzes muscle movement, structure, and purpose with the use of model simulations mechanisms and other software technology. In Running with a load increases leg stiffness, it is identified that added loads to the body impacts running posture, causing crouching of the body, and does contribute to higher leg stiffness. In line with Dr. Delp’s talk today of the “Dynamics of walking and running,” a comparison is established between both types of movement and the authors delve into how each are impacted when under a load (ranging from 10-30% body fat). Subjects walking and running under a load, compared to zero load, were to found to have longer ground

Metabolism comprises of a vital set of biochemical reactions that all living organisms require to sustain life. For a marathon runner, their physiological response to strenuous exercise depletes both their fats and carbohydrate storage in order to supply energy in the form of Adenosine Triphosphate (ATP). ATP is the energy form that the human body uses for biological processes such as movement and synthesis of biomacromolecules. In regards to running a marathon, the athlete is capable of using a combination of both anaerobic and aerobic pathways, but these different systems predominate at different intervals in order to increase the energy allowed for the muscles.

1. How is there a lower metabolic cost but with the higher forces during eccentric contraction?

To minimize movement, participants were secured to the bed with a non-elastic strap placed over their hips. The study allowed the participants to practice 3-5 s MVCs to ensure contractions could be performed consistently. After training peak oxygen consumption increased from 35.8±1.4 to 39.3±1.6 mL min, this also increased exercise capacity on the ergometer with no effects on total ATP production or force-time integral during the MVC. In the first session, 6 sessions increased contribution of ATPox from 31±2 to 39±2% of total ATP turnover.

During normal gait with functioning limbs, arm swing is key to saving metabolic cost. In an experimental trial by Collins, it was found that normal arm swing resulted in minimal shoulder torque, but by holding the arms still against one’s side, it was found to require 12% more metabolic energy. While this experiment was not pertaining to prostheses, it is seen that without freely swinging arms during gait there is an increase in metabolic cost. It was also found that vertical ground reaction moments increased by 63% when arm swing was eliminated. 5

The article “Muscular contributions to hip and knee extension during the single limb stance phase of normal gait: a Theoretical Framework for Crouch Gait” by Allison Arnold, Frank Anderson, Marcus Pandy, and Scott Delp investigates the biomechanics of normal gait in hopes to uncover ideas to help determine treatments for crouch gait. Crouch gait is a bothersome abnormality that affects the gait pattern of people who suffer from the condition of cerebral palsy. It’s characterized by excessive flexion of the hips and knees during standing and excessive use of metabolic energy to complete a single gait cycle. Currently, the treatments for this condition are limited and have unpredictable outcomes due to the unknown biomechanical causes of the excessive flexion in crouch gait. These treatments include surgical lengthening of hamstrings, ankle-foot orthoses, and intense stretching regimens, with patients experiencing results ranging from no improvement in their symptoms to dramatic improvements. The vast array of results from treatments are due to the little understanding medical professionals have of not only abnormal gait patterns (such as crouch gait) but of normal gait as well (Arnold, Anderson, Pandy, and Delp, 2005). Despite the article’s title relating to crouch gait, the purpose of the study conducted was to examine and quantify the accelerations of normal hip and knee movements that were induced by specific muscles during the single limb stance phase and to rank these

Another explanation of bipedalism is that walking upright reduce the energy consumption. Michael Sokol, a professor from University of California, Davis, David Raichlen, a professor from University of Arizona, Tucson, and Herman Pontzer, a professor from Washington University, St. Louis, conduct an experiment that examines the energy consumption level for both humans and adult chimpanzees. Their studies suggest that “early transitional forms would have reaped some energy savings with minor increases in hip extension and leg length.” According the research, they also conclude that energetics is an important factor in the evolution of bipedalism and the improved efficiency of locomotion “ may accrued very early within the hominin lineage.”

[4] Wagner J., Solis-Escalante T., Grieshofer P., Neuper C., Müller-Putz G., Scherer R. (2012). Level of participation in robotic-assisted treadmill walking modulates midline sensorimotor EEG rhythms in able-bodied subjects. Neuroimage, 63(3):1203-11. doi: 10.1016/j.neuroimage.2012.08.019. Epub 2012 Aug 14. PubMed PMID: 22906791.

With the mentioned arguments against the metabolic cost hypothesis the question is still remained that what governs the decision making process in control of gait and whether people always prioritize the metabolic cost over other preferences. In this study we revisited this question by giving subjects different choices of step rates to walk with and asked which ones were more desirable to them. The desirability of a condition has an inverse relationship with the cost of that condition. We hypothesize that subjects will not always choose step rates with lower metabolic cost but in the majority of conditions they will choose trials that have step rates and step lengths closer to their preferred walking conditions. If true, this hypothesis provides

“The analysis of movement provides an athlete with optimal development as well as minimising the risk of developing injuries through the incorrect execution of a movement” (Ackland, Elliott & Bloomfield, 2009, p 301).

Sockol et al argue that bipedalism evolved from a need to reduce the cost of locomotion, in other words It was more efficient and conserved more energy allowing for a higher locomotor economy. Sockel et al also talks about the involvement of “ muscle forces generated to support bodyweight” (Sockol et al 2007) which is the main factor behind the cost of land movement in the test subjects and therefore in locomotion costs (Sockol et al 2007).

To maintain effectiveness of muscle and bone activity, the effects of on the musculoskeletal system are the greatest benefits a person can ask for.

b. John P. Wiley comments on the benefits of walking by stating, "Being on your

Most of the time when exercise is being performed, it is perceived that there is a need or want to become healthy, or stay healthy. When the word healthy comes to mind the first instinct is to think of the health of the body; to lose weight, tone the muscles, increase strength. Today there is a big focus on exercise for its many benefits that have been found from research in recent years. With great focus on weight, diet, and reducing the risk of disease in the future. This is proven, we need exercise to keep the body systems healthy. It helps reduces weight, blood pressure, the risk of many diseases, and helps us lead a long healthy lifestyle. What most are blind to however, is that not only does exercise help with body composition and reduction of risk, but it can also help to increase the cognitive function of the brain. Exercise is the food for the brain. ?Studies in ageing humans show that endurance exercise is protective against cognitive decline, especially executive planning and working memory. In both humans and primates, exercise increases attention and performance on cognitive tasks? (Ploughman, 2008). Exercise is a must, not only for the benefits for the body systems, but most importantly for the brain. Most individuals exercise for reduction of disease risk to in turn