Skiing: It’s All About Friction

glide2It’s all about friction. Really. Friction from the snow, friction from the air, friction from the surface of the ski or the clothing you wear.  The physics of skiing is all about how to overcome drag and resistance and allow a skier to slice his/her way down the mountain.  And if Newton’s laws have anything to do with it, a skier who controls friction best has the best chance of winning.

Find out the basics of friction and skiing.

Articles by Marcia Howell

Skiing: It’s All About Friction (Basic)

glide3aWhen Bioengineer, Parker Tyler, goes skiing, she probably isn’t thinking about the biology or the physics behind the activity.  Rather, he is enjoying the crisp, cool, mountain air, the clear view of the slope, and the anticipated exhilaration he will feel as she maneuvers to the bottom. She likely doesn’t consider earth’s gravitational force (9.81 m/s), or potential energy, or kinetic energy, or her own mass, or any of those other factors that will contribute to his acceleration.  However, scientists do think about these things and their thinking has affected many facets of the industry from clothing to equipment to style.

It’s all about friction. Really. Friction from the snow, friction from the air, friction from the surface of the ski or the clothing you wear.  The physics of skiing is all about how to overcome drag and resistance and allow a skier to slice his/her way down the mountain.  And if Newton’s laws have anything to do with it, a skier who controls friction best has the best chance of winning.

Back to Parker, her potential energy is greatest at the top of the hill where she perches until the start of her run.  Her body is physically fit and adrenaline is taking over, sending added energy to her muscles, vision center, quick decision making regions of the brain, and the area that controls coordination.  Once she leaves starting position, gravity pushes down, mass pushes down, but the acceleration down the slope kicks in and changes how the forces affect the ride.  Potential energy turns into kinetic energy, or energy of motion, and everything he touches tries to resist and slow the movement.

Since Parker is a wise skier, she wears a GS suit (a sleek, form fitting suit with a minimum of abrasive surface area) and aerodynamic boots, hat (or helmet), gloves, etc.  As she accelerates, she assumes a crouching position to reduce air resistance and tighten the air current close to her body.  His skis are designed specifically for the type of skiing being done, the edges are sharp, and the bottoms are carefully waxed.  The wax waterproofs the skis, prevents them from drying out, and it reduces the wet drag of a kind of “suction” type friction from the snow.

When Parker comes to a curve, the skis will either be eased into the turn with the ski pointed in the same direction as her velocity, making a sharp cut in its wake, or she will choose a skidding type of maneuver where the skis will be forced in the direction she wishes to go, leaning away from the curve at a 45-90 degree optimal angle, and literally plowing snow away from her. Some skis have special designs that scientists have found will decrease the drag and increase the speed these curves can be safely made.  Surely, Parker will have researched and purchased those that fit his style and goals for skiing.

By the time she reaches the bottom, her potential energy is expended, the ensuing kinetic energy is maxed out, and now friction works against him to slow down her acceleration to a stop.  His adrenalin will return to normal levels, and her blood circulation and other systems will begin to function normally once again.  (At least until the next run.)

Research will continue to change the sport of skiing.  And no doubt, the savvy skier will keep tabs on the newest and best ways scientists will come up with to help us beat the forces working against us.

By: Marcia Howell, University of Utah

References:

Energy Transformation for Downhill Skiing. 2012. Retrieved from http://www.physicsclassroom.com/mmedia/energy/se.cfm

The Physics of Skiing. Real World Physics Problems. 2009. Retrieved from http://www.real-world-physics-problems.com/physics-of-skiing.html

Locke, B. 2012. The physics of skiing. Retrieved from http://ffden2.phys.uaf.edu/211_fall2002.web.dir/brandon_locke/Webpage/homepage.htm

Mears, A. 2002. Physics of Alpine Skiing. Retrieved from http://www.suberic.net/~avon/mxphysics/anne/Annie%20Mears.htm

How Chemistry Fuels the Body to Run

sports-usain-bolt-in-action-new-hd-wallpaper-usain-bolt-wallpaperUsain Bolt, the Jamaican sprinter who competed in the 2012 London Olympics, is widely known as the fastest man ever. Bolt is the first man in history to hold both the world records for the 100 meter and 200 meter sprint.  Running 100 meters in 9.58 seconds and 200 meters in 19.19 seconds required that he be able to produce and effectively use ample energy to support the strain he puts on all of the systems of his body.

Energy is derived from the food we put into our bodies and the oxygen we breathe. The food is chemically changed and metabolized at the cellular level (aerobically—with oxygen, anaerobically—without), which means it goes through processes that eventually convert it to ATP (adenosine triphosphate).   ATP is the source of energy that gives Bolt and other athletes the ability to do amazing things.

Learn the basics of how chemistry fuels running or read the more technical details.

Articles by Josh Sewell

How Chemistry Fuels the Body to Run (Basic)

Usain St. Leo Bolt, World Champion

sports-usain-bolt-in-action-new-hd-wallpaper-usain-bolt-wallpaperUsain St. Leo Bolt, a Jamaican sprinter who competed in the 2012 London Olympics, is widely known as the fastest man ever. Bolt is the first man in history to hold both the world records for the 100 meter and 200 meter sprint. He earned gold medals in both of these events at the 2008 and 2012 Olympics (Usain Bolt 2012). When sprinting, Bolt’s body must produce enough energy to run 100 meters in 9.63 seconds. There are amazing processes going on simultaneously within this runner’s body that are allowing this all to happen.

The Origin of Energy

Metabolic processes begin long before an athlete competes. In fact, the precursors to these processes begin at the dinner table. Energy begins in the form of a healthy meal consisting of carbohydrates, fatty acids, and amino acids. These “fuel” molecules are then metabolized into substances such as glucose, pyruvate, lactate, and the aforementioned acetyl-CoA.

The end product of these metabolic processes is a very important molecule called adenosine triphosphate (ATP). ATP is the molecule that supplies our body with the necessary energy to perform. The cells that make up our body all use ATP to perform many necessary functions such as cell signaling (Bell et al. 2003), transport of molecules in and out of cells (Skou 1965), muscle contraction (Adelstein and Eisenberg 1980), and even for the synthesis of more ATP through our metabolism (Champe and Harvey 1987, Campbell et al. 2005). Through cell signaling, ATP allows our central and peripheral nervous system to function properly (Bell et al. 2003), it allows actin and myosin crossbridges in our muscles to function so that we can flex and contract muscles (Adelstein and Eisenberg 1980), allowing us to move and perform. In our metabolism, ATP is used to allow glycolysis to continue, which in turn produces more ATP (Champe and Harvey 1987, Campbell et al. 2005). When our body has low levels of ATP, it knows when to produce more and will increase the rate of glycolysis and the citric acid cycle accordingly.

Glycolysis

Glycolysis literally translated means to split sugar (Glucose—sugar, lyse—to split). Glycolysis can be aerobic when we have sufficient oxygen, or anaerobic when the oxygen in our system is low. Virtually all sugars can be converted to glucose which is free to diffuse in and out of the cells that make up the different tissues of our body. Glycolysis is a process that ends up in a net formation of two ATP molecules per glucose molecule.

Anaerobic Glycolysis

Anaerobic glycolysis takes place without oxygen and is the way our metabolism supplements the demand for short, intense bursts of energy. Events lasting approximately 10 seconds or somewhat longer (e.g. 100-m run) utilize anaerobic glycolysis for energy in ATP production (Knuttgen and Komi 2003). This can only be sustained for short periods of time (Knuttgen and Komi 2003).  Lactic acid is produced during anaerobic glycolysis and is responsible for the burning sensation sometimes felt in muscle fibers.

Aerobic Glycolysis and The Citric Acid Cycle

When there is adequate oxygen in the body, aerobic glycolysis takes place and is coupled to the citric acid cycle. The citric acid cycle yields much more energy than glycolysis alone. If we add all of the energy yielding products of the breakdown of one glucose molecule, we can obtain 15-17 times more ATP through the breakdown of one glucose molecule.

Learn the technical details about the chemistry of running.

By: Josh Sewell, University of Utah
Joshua Sewell graduated from Brigham Young University-Idaho with a Bachelor’s of Science in chemistry and a minor in biology. He is fascinated by biochemistry and the processes that make the body work. Josh is currently a graduate student working on a Ph.D. in chemical engineering where he is focused on microbially enhanced coalbed methane recovery and applications. Outside of the lab, Josh enjoys spending time with his wife, Sara, and his two daughters, Oakley and Zoe.

References:

Adelstein, R. S., & E. Eisenberg. 1980. Regulation and Kinetics of the Actin-Myosin-ATP Interaction. Annual Review of Biochemistry 49: 921-56.

Bell, P. D., J.Y. Lapointe, R. Sabirov, S. Hayashi, J. Peti-Peterdi, K. Manabe . 2003. Macula densa cell signaling involves ATP release through a maxi anion channel. Proceedings of the National Academy of Sciences of the United States of America 100 (7): 4322-27.

Ericinska, M., & F. Dagani. 1990. Relationships between the neuronal sodium/potassium pump and energy metabolism. Effects of K+, Na+, and adenosine triphosphate in isolated brain synaptosomes. The Journal of General Physiology 95 (4): 591-616.

Knuttgen, H. G., & P.V. Komi. 2003. Basic Considerations for Exercise. In P. V. Komi (Ed.). Strength and Power in Sport (Vol. 3). Blackwell Science, Malden, Massachusetts, USA.

Champe, P., & R.A. Harvey. 1987. Lippincott’s Illustrated Reviews: Biochemistry. J.B. Lippincott Company, Philadelphia, Pennsylvania, USA.

Campbell, P. A. Smith, & T. Peters. 2005. Biochemistry Illustrated, Biochemistry and molecular biology in the post-genomic era (Fifth ed.). Elsevier Churchill Livingstone, Edinburgh, Scotland.

Skou, J. 1965. Enzymatic basis for active transport Na+ and K+ across cell membrane. Physiological Reviews 45 (3): 596-618.

Usain Bolt. (2012, August). Usain Bolt. Retrieved from http://usainbolt.com/bio/.com/bio/

How Chemistry Fuels the Body to Run (Technical)

Usain St. Leo Bolt, World Champion

Usain St. Leo Bolt (See Figure 1), a Jamaican sprinter who competed in the 2012 London Olympics, is widely known as the fastest man ever. Bolt is the first man in history to hold both the world records for the 100 meter and 200 meter sprint. He earned gold medals in both of these events at the 2008 and 2012 Olympics (Usain Bolt 2012). When sprinting, Bolt’s body must produce enough energy to run 100 meters in 9.63 seconds. There are amazing processes going on simultaneously within this runner’s body that are allowing this all to happen.

Figure 1: Usain St. Leo Bolt4

Aerobic and Anaerobic Respiration

To understand what is going on in an athlete’s body, we must first understand the difference between aerobic respiration and anaerobic respiration. When an athlete runs, there is a high demand for oxygen and a limited supply. A Sprinter like Bolt finishes a race before he is able to breathe heavier and accrue more oxygen. For the most part, Bolt’s body is running on a process called anaerobic glycolysis (Kudo et al. 1996). Anaerobic essentially means “without oxygen.” Anaerobic glycolysis allows his body to produce limited energy when he has low levels of oxygen in his system. Every time Bolt takes a breath, his body is supplied with a very limited amount of oxygen that is instantly used to fuel a process that yields much more energy: aerobic glycolysis coupled to the citric acid cycle (also known as Kreb’s cycle or the tricarboxylic acid cycle) by acetyl coenzyme A (Acetyl CoA). Acetyl-CoA is produced when the oxygen supply in our body is abundant. This is one of the reasons we breathe more heavily when we engage in physical activity. Our body has feedback mechanisms that tell us to breathe in more oxygen to allow our body to produce energy at a faster pace (Skou 1965, Lamb and Stephenson 2006b).

The Origin of Energy

Metabolic processes begin long before an athlete competes. In fact, the precursors to these processes begin at the dinner table. Energy begins in the form of a healthy meal consisting of carbohydrates, fatty acids, and amino acids. These “fuel” molecules are metabolized into substances such as glucose, pyruvate, lactate, and the aforementioned acetyl CoA.

The end product of these metabolic processes is a very important molecule called adenosine triphosphate (ATP). ATP is the molecule that supplies our body with the necessary energy to perform. The cells that make up our body all use ATP to perform many necessary functions such as cell signaling (Bell et al. 2003), transport of molecules in and out of cells (Winder and Hardie 1996), muscle contraction (Adelstein and Eisenberg 1980), and metabolism (Skou 1965, Lamb and Stephenson 2006b). Through cell signaling, ATP allows our central and peripheral nervous system to function properly (Bell et al. 2003). It allows actin and myosin crossbridges in our muscles to function so that we can flex and contract muscles (Adelstein and Eisenberg 1980), allowing us to move and perform. In metabolism, ATP allows glycolysis to continue, which in turn produces more ATP (Skou 1965, Lamb and Stephenson 2006b). ATP is one of the most important molecules in our body because essentially, it gives the cells in our body the ability to perform all the functions necessary to sustain life. Studies have shown that a decrease in ATP is the chief factor responsible for increased energy production.5 When our body has low levels of ATP, it knows when to produce more and will increase the rate of glycolysis and the citric acid cycle accordingly.

Glycolysis

Glucose

Glycolysis literally translated means to split sugar (Glucose—sugar, lyse—to split). Virtually all sugars (whether arising from our diet or from catabolic reactions in the body) ultimately can be converted to glucose; glucose is free to diffuse in and out of the cells that make up the different tissues of our body. Diffusion generally occurs from areas of high concentration to areas of low concentration. For this reason, when cells are depleted of glucose, more is able to be supplied through diffusion.

Glycolysis can be aerobic when we have sufficient oxygen, or anaerobic when the oxygen in our system is low. The reactions involved with glycolysis begin in the same pathway, regardless of the amount of oxygen present.

Glycolysis (See Figure 2) begins when a phosphorous molecule is added to the glucose molecule to form glucose 6-phosphate. This process is called phosphorylation and in this case, the phosphorylation is performed by an enzyme called hexokinase. Enzymes are biocatalysts that speed up reactions such as this one. The phosphorylation is irreversible. Once the phosphorylation occurs, the glucose molecule is blocked from leaving the cell without some kind of special carrier molecule. This commits the glucose molecule to the glycolysis process. The phosphorylation of glucose uses the phosphorous from an ATP molecule, which almost seems counterproductive since ATP is what glycolysis is trying to produce, but we can consider this an investment since more ATP will be produced further along in the process. When the ATP gives up a phosphorus molecule, it is converted to adenosine diphosphate (ADP).

Next, the enzyme phosphoglucose isomerase converts glucose 6-phosphate to fructose 6-phosphate. Fructose 6-phosphate is an isomer of glucose 6-phosphate, which means that they have the same chemical formula (i.e. they are made of the same number and type of atoms) but a different structural formula. This means that they are made up of the same atoms, but they are shaped differently. After isomerization, phosphofructokinase (an enzyme) phosphorylates fructose 6-phosphate to form fructose 1,6-bisphophate. An additional investment of ATP is made in the phosphorylation of fructose 6-phosphate. This makes two total ATP molecules invested into glycolysis for each molecule of glucose. Soon we will see why glycolysis is worth the investment of energy in the “payoff” phase.

Once fructose 1,6-bisphophate is made, it is cleaved (or split) into dihydroxyacetone phosphate and glyceraldehyde 3-phosphate by the enzyme Aldolase. This is the ‘lysis or lyse’ step in glycolysis. Dihydroxyacetone phosphate is a precursor molecule only and cannot proceed further down the pathway of glycolysis without modification. Triose phosphate isomerase (an enzyme) catalyzes the reversible conversion of dihydroxyacetone phosphate to another molecule of glyceraldehyde 3-phosphate. This increases the total number of glyeraldehyde 3-phosphate molecules to two per molecule of glucose metabolized.

The glyceraldehyde 3-phosphate molecules are oxidized to 1,3-diphosphoglycerate by glyceraldehyde 3-phosphate dehydrogenase (an enzyme). This is an oxidation-reduction reaction converting nicotinamide adenine dinucleotide (NAD+) to a reduced form (NADH) and phosphorylating each of the glyceraldehyde 3-phosphate molecules to form 1,3-diphosphoglycerate (Skou 1965, Lamb and Stephenson 2006b). Glycolysis is closely regulated by the amount of NAD+ to NADH in our system (Witters et al. 1994). You can imagine that if there is a large buildup of NADH and not much NAD+ available, this step will slow down the rate of glycolysis.

Each 1,3-diphosphoglycerate is used to form an ATP using the enzyme Phosphoglycerate kinase and an ADP molecule (remember that two ADP were created in the investment of ATP in the earlier stages of glycolysis). This forms two ATP molecules so that the net production of ATP is now zero per molecule of glucose. 3-phosphoglycerate is the resulting molecule from each 1,3-diphosphoglycerate.

Next, the phosphate atom is shifted on the #3 carbon of 3-phosphoglycerate to #2 carbon by phosphoglyceromutase to form 2-phosphoglycerate. 2-phopshoglycerate is then dehydrated by the enzyme enolase to form phosphoenolpyruvate (PEP). The next reaction forms the molecule pyruvate. Pyruvate is formed by the enzyme pyruvate kinase producing an additional ATP molecule from each PEP molecule. Two ATP molecules are formed for each glucose molecule. This gives a net of two ATP molecules for each molecule of glucose metabolized. The resulting pyruvate molecule is where anaerobic glycolysis and aerobic glycolysis differ (Skou 1965, Lamb and Stephenson 2006b).

Anaerobic Glycolysis

Sprinting, lifting weights, and short bursts of energy within aerobic exercise are all fueled by anaerobic respiration. When Bolt is sprinting, his oxygen demand exceeds the supply. Anaerobic glycolysis is the way our metabolism supplements the energy demand for these short, intense bursts of activity. Events lasting approximately 10 seconds or somewhat longer (e.g. 100-m run) utilize anaerobic glycolysis for energy in ATP production (Kudo et al. 1996).

Remember, the NADH that was formed in the oxidation-reduction reaction in glycolysis. When oxygen levels are low, this NADH reacts with the pyruvate leftover from glycolysis to form lactate and NAD+. This NAD+ is then recycled and used to allow the glyceraldehyde 3-phosphate molecules to be oxidized to 1,3-diphosphoglycerate in glycolysis allowing the glycolysis cycle to continue to produce more ATP (Skou 1965, Lamb and Stephenson 2006b). This can only be sustained for short periods of time (Kudo et al. 1996). Once our body adjusts to the strenuous activity and the energy demand by breathing in oxygen, aerobic glycolysis kicks in.

It is interesting to know that production of lactate and other metabolites during extreme exertion results in the burning sensation that is felt in active muscles. While lactic acid accumulation inside muscle fibers is responsible for the burning sensation we feel, it is not responsible for decreased muscle performance (“muscle fatigue”). There are several broad types of muscle fatigue, and the contribution of each to the overall decline in performance depends on the muscle fiber type and the intensity and duration of the activity (Tilton et al. 1991). Arguments have been made that lactic acid buildup in active muscles is advantageous and other arguments have countered saying that it is disadvantageous (Witters et al. 1994). Those that advocate that lactate is advantageous make the argument that the lower intracellular pH, due to the acidity of lactate, counters the effects of high potassium levels which inhibit membrane transport channels from functioning at full capacity (Tilton et al. 1991). Those that argue that lactate has an inhibitory effect report that lactate induced an impairment of calcium release channels (Bangsbo and Juel 2006). Calcium plays a crucial role in muscle contraction (Kudo et al. 1995), so this argument makes a valid point as well.

Figure 2: Glycolysis6

Aerobic Glycolysis and Acetyl CoA

For longer distance running, when oxygen supply is able to meet the demand, oxidative decarboxylation of pyruvate occurs to form Acetyl CoA yielding an NADH for each pyruvate. This occurs in cells that contain mitochondria. The mitochondria are considered “the powerhouses of the cell” because they are where the citric acid cycle occurs. Oxidative decarboxylation of pyruvate by the enzyme pyruvate dehydrogenase converts pyruvate (inside the mitochondrial matrix) to acetyl CoA.

Acetyl CoA is the precursor to the citric acid cycle (Skou 1965, Lamb and Stephenson 2006b).

The Citric Acid Cycle

The citric acid cycle is an eight-step process after pyruvate has been converted to acetyl CoA (See Figure 3). It begins by the condensation of acetyl CoA and oxaloacetate to form citrate by the enzyme citrate synthase. Next is the isomerization of citrate to isocitrate, a molecule with the same number of atoms, with a different makeup. After isomerization, oxidation and decarboxylation of the resulting isocitrate occurs. This converts isocitrate to alpha-ketoglutarate and is catalyzed by the enzyme isocitrate dehydrogenase. This is another oxidation-reduction reaction and requires an NAD+ molecule. This forms the first of three NADH molecules.

This reaction is followed by another oxidation-reduction reaction. Oxidative decarboxylation of alpha-ketoglutarate to form succinyl CoA by alpha-ketoglutarate dehydrogenase complex occurs. This forms another NADH from NAD+. Succinate kinase catalyzes the cleavage of succinyl CoA to form succinate. The cleavage of succinyl CoA produces a guanosine triphosphate (GTP), which contains the same energy content as an ATP molecule. After succinate is formed, it is oxidized, in another oxidation-reduction reaction, to form fumarate. Since the reducing power of succinate is not sufficient to reduce NAD+ to NADH, the oxidation-reduction reaction is enabled this time by the molecule flavin adenine dinucleotide (FAD). This forms the reduced form of FAD, FADH2. Fumarate is then hydrated to the molecule malate by the enzyme fumarase.

The final step of the citric acid cycle is the oxidation of malate to oxaloacetate catalyzed by the enzyme malate dehydrogenase. This produces the third and final NADH molecule and leaves an oxaloacetate molecule to react with acetyl CoA to renew the cycle. Keep in mind that for each glucose molecule, two molecules of acetyl CoA are formed. This produces a total of six NADH molecules, two FADH2 molecules, and two GTP molecules for each glucose molecule. If we add all of the energy yielding products of the breakdown of one glucose molecule, we have a total of ten NADH molecules, two FADH2 molecules, two GTP molecules, and a net of four ATP molecules. Each NADH is capable of producing 3 ATP, each FADH2 is capable of producing 2 ATP, and each GTP is equivalent to one ATP. This yields a total of 38 ATP assuming that all of these products go on to produce an ATP. We can now see why we need more oxygen when we work hard over longer distances. The oxygen is essential to allow glycolysis to link to the citric acid cycle and produce more energy to sustain us (Skou 1965, Lamb and Stephenson 2006b).

Figure 3: The Citric Acid Cycle11

Summary – How does this affect running?

As Bolt lines up at the starting line, he listens for the starting gun. His body has already started to produce extra ATP because of his warm-up exercises. As the gun goes off, ATP begins working in conjunction with actin and myosin fibers that make up his muscles, enabling him to contract his muscles and move. His central and peripheral nervous system communicate with his muscles through cell signaling, which is enabled by ATP. His cells start to notice a lack of ATP, which signals the production of pyruvate through glycolysis. With each breath of air, oxygen molecules diffuse from his lungs into his bloodstream and finally into his cells where they allow oxidative decarboxylation of pyruvate forming acetyl CoA. Acetyl CoA allows the metabolism of oxaloacetate in the citric acid cycle to produce more ATP. As his cells are starved of oxygen between breaths, anaerobic glycolysis occurs and pyruvate is fermented into lactate in his muscles, producing a burning sensation in his muscles. Bolt crosses the finish line well ahead of his competitors, all made possible by the adenosine triphosphate produced during metabolism.

 

By: Josh Sewell, University of Utah
Joshua Sewell graduated from Brigham Young University-Idaho with a Bachelor’s of Science in chemistry and a minor in biology. He is fascinated by biochemistry and the processes that make the body work. Josh is currently a graduate student working on a Ph.D. in chemical engineering where he is focused on microbially enhanced coalbed methane recovery and applications. Outside of the lab, Josh enjoys spending time with his wife, Sara, and his two daughters, Oakley and Zoe.

 

 

References:

Adelstein, R. S., and E. Eisenberg. 1980. Regulation and Kinetics of the Actin-Myosin-ATP Interaction. Annual Review of Biochemistry 49: 921-56.

Bangsbo, J., and C. Juel. 2006. Lactic acid accumulation is a disadvantage during muscle activity. Journal of Applied Physiology 100 (4): 1410-12.

Bell, P. D., J.Y. Lapointe, R. Sabirov, S. Hayashi, J. Peti-Peterdi, K. Manabe . 2003. Macula densa cell signaling involves ATP release through a maxi anion channel. Proceedings of the National Academy of Sciences of the United States of America 100 (7): 4322-27.

Ericinska, M., and F. Dagani. 1990. Relationships between the neuronal sodium/potassium pump and energy metabolism. Effects of K+, Na+, and adenosine triphosphate in isolated brain synaptosomes. The Journal of General Physiology 95 (4): 591-616.

Karaki, H., H. Ozaki, M. Hori, M. Mitsui-Saito, K. Amano, K. Harada. 1997. Calcium Movements, Distribution, and Functions in Smooth Muscle. Pharmacological Reviews 49 (2): 157-230.

Knuttgen, H. G., and P.V. Komi. 2003. Basic Considerations for Exercise. In P. V. Komi (Ed.). Strength and Power in Sport (Vol. 3). Blackwell Science, Malden, Massachusetts, USA.

Kudo, N., A. Barr, R. Barr, S. Desai, and G. Lopaschuk. 1995. High rates of fatty acid oxidation during reperfusion of ischemic hearts are associated with a decrease in malonyl-coA levels due to an increase in 5’-AMP-activated protein kinase inhibition of acetyl-coA carboxylase. Journal of Biological Chemistry 270: 17513–17520

Kudo, N., J. Gillespie, K. Kung, L. Witters, R. Schuz, S. Clanachan, and G. Lopaschuk. 1996. Characterication of 5’AMP-activiated kinase activity in the heart and its role in inhibiting acetyl-CoA carboxylases during reperfusion following ischemia. Biochimica et Biophysica Acta 1301: 67–75

Champe, P., and R.A. Harvey. 1987. Lippincott’s Illustrated Reviews: Biochemistry. J.B. Lippincott Company, Philadelphia, Pennsylvania, USA.

Campbell, P. A. Smith, and T. Peters. 2005. Biochemistry llustrated, Biochemistry and molecular biology in the post-genomic era (Fifth ed.). Elsevier Churchill Livingstone, Edinburgh, Scotland.

Lamb, G. D., and D.G. Stephenson. 2006a. Lactic acid accumulation is an advantage during muscle activity. Journal of Applied Physiology 100 (4): 1410-12.

Lamb, G. D., and D.G. Stephenson. 2006b. Point Counterpoint: Lactic acid accumulation is an advantage/disadvantage during muscle activity. Journal of Applied Physiology 100 (4): 1410-12.

Skou, J. 1965. Enzymatic basis for active transport Na+ and K+ across cell membrane. Physiological Reviews 45 (3): 596-618.

Tilton, W., C. Seaman, D. Carriero, and S. Piomelli. 1991. Regulation of glycolysis in the erythrocyte: role of the lactate/pyruvate and NAD/NADH ratios. The Journal of Laboratory and Clinical Medicine 118 (2): 146-52.

Usain Bolt. (2012, August). Usain Bolt. Retrieved from http://usainbolt.com/bio/

Winder, W.W. and D.G. Hardie. 1996. Inactivation of acetyl-CoA carboxylase and activation of AMP-activated protein kinase in muscle during exercise. American Journal of Physiology 270: 299–304.

Witters, L. A., G. Gao, B. Kemp, and B. Quistorff. 1994. Hepatic 5’-AMP-activated protein kinase: zonal distribution and relationship to acetyl-CoA carboxylase activity in varying nutritional states. Arch. Biochem. Biophys. 308: 413–419.

Materials Science: Wood vs. Aluminum Bats (Basic)

It is common knowledge that metal baseball bats perform better in competition than wooden bats. The question is…why? There are several factors that explain why metal and wooden bats have such a disparity in performance.

In a 1977 study (when aluminum bats were first beginning to show up on the scene) using college players taking batting practice, it was shown that line drives coming off the wooden bat registered at 88.6 miles per hour while the aluminum bat registered batted ball speeds upwards of 92.5 miles per hour. This may not seem like a huge difference but it is large enough to, in some cases, take a pop fly and turn it into a home run.

The first reason metal bats outperform their wooden counterparts is that they are hollow. The hollow nature of metal bats allow them to be swung at a faster speed even if they are the same weight as a wooden bat. This is because the center of mass of the metal bat is closer to the handle and this allows a hitter to control more of bat’s mass and bring it through the hitting zone at a faster speed. This higher bat speed will produce faster batted ball speeds and send the ball farther.

With the center of mass closer to the handle, the bat has a lower moment of inertia. Inertia is the tendency of an object to resist motion. It is a function of mass and the square of a distance. With the center of mass closer to the handle, a hitter has to put in less work to moving the bat and swing at a higher speed.

When a ball is struck by a solid wood bat, the ball is compressed up to 75% of its diameter. A lot of energy goes in to this deformation and this will take away from the energy the ball will have when it leaves the bat. The hollow metal bat acts sort of like a spring and more of the energy from the hitter is able to be transferred into the ball and send it farther.

Finally, metal bats do not break! When a wooden bat shatters, up to 80% of its energy can be lost. Batted balls rarely travel far when a bat is broken in a swing. This obviously does not occur in metal bats because of the strength of the material. This is also much cheaper for baseball teams as the need a small number of aluminum bats compared to the hundreds gone through by teams with wooden bats.

A study conducted that tested distances based on batted ball speeds using metal and wooden bats showed drastic results. Each ball was angled at 35 degrees and the batted ball speed was measured. A ball hit at 98.8 mph with a wooden bat will travel around 388 feet. A ball hit at a speed of 101.5 mph with a metal bat will travel just over 400 feet and a ball hit it a whopping 106.5 mph with a metal bat will travel upwards of 425 feet. This test shows that one of the major factors in the distance a ball travels is bat speed and higher bat speeds can be offered by metal bats!

(Note: The above can also be used to explain the differences between metal and wooden golf clubs!!)

By: Kenny Morley, Ohio State University 

 

References:

Russel, D. A.. Why Aluminum Bats Can Perform Better than Wood Bats. Retrieved from http://www.acs.psu.edu/drussell/bats/alumwood.html

Maddox, D. (2012). Altitude Plays a Big Role in Denver Baseball. Retrieved from http://voices.yahoo.com/altitude-plays-big-role-denver-baseball- 289433.html

Getting Punting Down to a Science (Basic)

Before the punter is able to punt the ball, there are several other elements he needs. First…the ball. One interesting fact about kickers is that they get their own balls inscribed with a K that is used in the game only for kicking. NFL Footballs are filled to between 11 and 13 psi but the special kicking balls are always filled to the highest possible pressure of 13 psi. PSI stands for pounds per square inch and this literally means that there is between 11 and 13 pounds of pressure pushing on each square inch of the football. When the air pressure is increased, the elasticity also increases. Elasticity is essentially how well the football is able to release energy and convert it into movement. With high pressure in the ball, the gases that expand when the ball is kicked are able to transfer energy to motion much easier than if their was less air pressure. Kickers have also been known to be very protective of their footballs. They rub them down with a horsehair brush and this removes the film and shows the stickier surface. This allows a punter to hold on to the snap much easier. The horsehair brush also firms up the ball and this increases the elasticity of the ball even further.

Finally, the punter is ready to step onto the field and do what he does best: punt the ball. Before the snap, a punter typically stands around 14 yards behind the ball. The first important part of the punt is the snap. The long snapper needs to get the ball the 14 yards into the punters hands. To do this, he must spin the ball in a counter-clockwise motion and throw it through his legs with considerable force. This spinning, similar to a bullet coming out of a gun, makes the football fly much straighter and makes it easier for the punter to catch.

When the snap is received, the punter will take 2 steps and attempt to drop the ball level or with the nose of the ball tilted slightly up. It is essential to kick as much of the ball as possible so that more force is transferred from the punters foot into the ball. Dropping the ball straight down allows for the punter to get his foot on a large portion of the ball, but it also allows him to put spin on the ball. This spin not only makes the punt more accurate, but it also causes the ball to stay in the air longer (this is called “hang-time”).

When the ball is finally kicked it becomes a projectile and follows the rules of projectile motion. The angle of the ball, when it leaves the punters foot, is very important. The ideal angle for the longest kick would be 45 degrees but different game situations may call for a different angle. For example, if the punter wanted to kick the ball higher, he would use an angle greater than 45 degrees to achieve that height. The ball flies in a parabolic shape and its motion can be described using vectors.  Vectors are lines that describe the velocity and the direction of an object in motion, which in this case is the football. A punted football has a vertical velocity vector as well as a horizontal velocity vector. The vertical vector describes how the football is moving up and down while the horizontal vector describes the motion relative to the ground.  When the football is at its highest, the vertical velocity vector is 0 and this is where punters want the spin of the ball to help hold it in mid-air. The longer the ball is able to stay at this point, the higher the hang-time and the farther the ball will fly.

Some equations that will govern the flight of the football include:

  • Range:
  • Height at specific time:
  • Distance at specific time:

 

Where V0 = initial velocity

Vy0 = initial vertical velocity

Vx0 = initial horizontal velocity

t = time

g = acceleration due to gravity

Θ = angle of the kick

By: Kenny Morley, Ohio State University 

 

References:

Freudenrich, C. (2012). How the physics of football works. Retrieved from http://www.howstuffworks.com/physics-of-football2.htm