Instructor note: A good instructor resource for the material presented in this lecture is provided in the Lesson-1 folder (Brown SP. Exercise Physiology. In: Brown SP, ed. Introduction to Exercise Science. Baltimore: Lippincott Williams & Wilkins; 2001. ).

1

Exercise physiology is the study of the body’s response and adaptation to exercise.

2

We will begin by discussing the major body systems that adapt to exercise. There are many more adaptations to exercise than are listed here. These are the most important in terms of physical performance.

3

The purpose of the respiratory system is gas exchange. Specifically, oxygen diffuses across the alveoli and is loaded on hemoglobin molecules in the red blood cells of the capillaries surrounding the lung. Oxygen moves in a diffusion gradient. The concentration in the lung is greater than the concentration in the capillary circulation. At sea level, blood leaving the lung is 98% (or more) saturated with oxygen. Even in conditions of very hard exercise, blood oxygen saturation does not typically drop (with the exception of a few highly elite athletes, where a very small drop can occur). This means that delivery of oxygen to the bloodstream by the lungs is not a limiting factor for exercise performance. The other gas that is exchanged in the lung is CO2 (carbon dioxide). The body produces carbon dioxide as a by product of producing energy from carbohydrates, fat and protein. Blood that arrives at the lung has a high concentration of CO2 due to these metabolic processes (even more during exercise), so CO2 flows from the bloodstream to the lungs (the opposite of the direction of travel of oxygen). Carbon dioxide is offloaded and oxygen is on loaded at the lung/capillary interface. Strength training has little impact on lung function. Endurance/aerobic training can increase the efficiency and fatigue resistance of the diaphragm (muslce that inflates the lungs) and the intercostals and abdominal muscles that are active during very heavy breathing. Endurance/aerobic training can also increase maximal ventilation rate. Reference: Essentials of Exercise Physiology, Second Edition, McArdle, W.D., Katch, F.L., and Katch, V.L., Chapter 10, Page 229-260, Chapter 14, Page 373-374 Lippincott Williams & Wilkins, 2000.

4

The cardiovascular system consists of the heart, blood and circulatory system (arteries, arterioles, capillaries, venules and veins). The purpose of the cardiovascular system is to deliver blood to all parts of the body. Blood carries oxygen, nutrients, hormones and other substances necessary for body function. The heart has a right side and a left side with separate pumps. The right side of the heart receives blood from the body and pumps blood to the lungs. The left side of the heart receives blood from the lungs and pumps it out to the rest of the body. Because the left side does more work, it is comprised of a larger chamber and more muscular walls. Strength training can produce some changes in the heart. The heavy straining and increased pressure in the thoracic cavity during heavy lifts can produce a large back pressure for the heart to work against. This can result in a thickening or hypertrophy of the left ventricular muscular wall. Total stroke volume (blood pumped with each beat of the heart) can increase slightly as well. In the muscle tissue, capillary density (how much capillary area per square centimeter) can decrease as the muscle grows larger. This is thought to reduce the aerobic capacity of the muscle by reducing the capacity to deliver oxygen rich blood to all parts of the muscle rapidly. However, the impact of this adaptation is small and probably unimportant. Endurance or aerobic training can produce substantial changes in the cardiovascular system. The left ventrical (main pump) gets larger and stronger, pumping more blood per beat (increased stroke volume). Because maximum heart rate is fixed, this adaptation allows an athlete to pump more blood at the highest work levels. It is also partially responsible for a lower resting heart rate (more blood pumped per beat = fewer beats per minute necessary). A greater stroke volume results in a lower heart rate at any given work rate. For example, after completing a training program a runner will have a lower heart rate at the same running speed, compared to before completing the training program. Blood volume and capillary density, especially in the muscles, is increased, resulting in more muscle blood flow. Together these adaptations result in a greater capacity to deliver blood to working muscles. Blood pressure can also decrease with endurance or aerobic training. There is some evidence to suggest that the decline in maximum heart rate with age can be reduced with regular endurance exercise. The ability to deliver sufficient oxygenated blood to working muscles is a primary determinant of maximum aerobic capacity, often referred to as VO2 max (maximum rate of oxygen consumption). A high VO2 max is associated with a high potential for aerobic/endurance sports. The aforementioned adaptations can increase aerobic capacity and VO2 max. Reference: Essentials of Exercise Physiology, Second Edition, McArdle, W.D., Katch, F.L., and Katch, V.L., Chapter 11, Page 263-294, Chapter 14, Page 370-373, Chapter 15, Page 415, Lippincott Williams & Wilkins, 2000.

5

The signal to initiate muscle contraction comes from a motor nerve. Typically, a motor nerve controls several muscle cells (from just a few, to over 100). A motor nerve and the muscle cells that it controls are together called a motor unit. All of the muscle cells within a motor unit share similar characteristics. We classify muscle fiber types according to these characteristics. There are 3 basic muscle fiber types: fast twitch – large, high force, powerful fibers that fatigue rapidly, store lots of glycogen and respond well to strength training; slow twitch – smaller fatigue resistant fibers that have a high aerobic capacity, are very fatigue resistant, respond well to aerobic/endurance training but do not respond well to strength training. Intermediate fibers have characteristics that are in between fast and slow twitch. When the motor nerve sends a signal, all of the muscle cells in that motor unit will contract. Muscles contain many motor units. The amount of force produced by a muscle is controlled primarily by turning on more or fewer motor units. This is done in a specific order and follows Henniman’s Size Principle of Muscle Fiber recruitment. At low force levels, small, slow twitch motor units are recruited. As the force level increases, intermediate motor units are recruited. At high force levels, large, fast twitch motor units are recruited. Large initial forces are required to produce explosive/fast movements, so large, fast twitch fibers are recruited to produce very rapid movements, even with lighter loads. Novice weight lifters are unable to recruit all available motor units. Advanced lifters can recruit 95% or more of the available motor units. Strength training results in an increase in the size of muscle cells, especially fast twitch muscle. Through repeated training, fast twitch muscle cells begin to take on the characteristics of intermediate muscle fibers. This improves their fatigue resistance, while retaining the high force and hypertrophy potential of fast twitch fibers. The ability to recruit a higher % of available motor units is one of the first adaptations to a strength training program. This results in increased strength, even before any hypertrophy occurs. Endurance training can cause the aforementioned fast twitch to intermediate muscle fiber conversions. This type of training can also cause intermediate fibers to take on some of the characteristics of slow twitch fibers, particularly their ability for high levels of aerobic metabolism and fatigue resistance. High volume endurance training may result in decreased muscle size. Long endurance sessions (<90 minutes) can produce a catabolic hormone profile, resulting in muscle protein breakdown and the use of the protein for metabolic energy production. Elite endurance athletes often have less muscle mass than sedentary adults. Flexibility training (stretching) results in lengthening the muscle fibers and the tendons, which connect muscles to bones. Reference: Essentials of Exercise Physiology, Second Edition, McArdle, W.D., Katch, F.L., and Katch, V.L., Chapter 12, Page 297-326, Chapter 15, Page 389-424, Lippincott Williams & Wilkins, 2000.

6

The purpose of the metabolic systems is to provide energy for all body processes, including movement. There are 3 basic metabolic pathways or systems. The phosphagen system is a short duration system. It can produce a very large amount of energy, but only for a short duration. The phosphagen system can fuel activities up to about 10 seconds in duration. After approximately 10 seconds, phosphagen energy stores start to decline and sustainable power output declines as well. If you did an all out sprint, you would begin to slow significantly after 10 seconds due to depletion of the phosphagen system energy stores. For longer duration activities that do not exceed 2 minutes, the primary energy system used is the glycolytic system. This is an anaerobic (without oxygen) system that is also high capacity (but not as high as the phosphagen system), but glycolytic system energy production starts to decline rapidly after one minute. The glycolytic system produces lactate (lactic acid) as a by product. For events that last longer than 2 minutes, the aerobic energy system provides most of the energy. This system can provide energy indefinitely and is the primary system providing energy to your body at rest and during lower intensity exercise. The aerobic/oxidative system has a large capacity but a much lower energy production rate than the other two systems (lasts a long time but does not provide as much short term energy). A 40 yard sprint would rely mainly on the phosphagen system. A 440 yard run would rely mainly on the glycolytic system. A 10K run would rely mainly on the aerobic/oxidative system. Reference: Essentials of Exercise Physiology, Second Edition, McArdle, W.D., Katch, F.L., and Katch, V.L., Chapter 5, Page 125-140, Lippincott Williams & Wilkins, 2000.

7

Many other body systems respond to exercise. Load bearing exercises (i.e. running, weight training) results in increased bone density. Hormone profiles change with exercise training. Experienced weight lifters produce more testosterone after training sessions. Trained athletes have a lower stress response (adrenaline hormones) to hard exercise. Also, our digestive system becomes better at accepting and processing fueling during exercise.

8

Next we will discuss some of the basic principles of exercise and conditioning.

9

The principle of specific adaptation to imposed demands simply means that you get better at what you do. The training demands placed on the body will determine how the body responds and what results will occur. Reference for the next 3 slides: 1. Implications and applications for training specificity for coaches and athletes,

Strength and Conditioning Journal, 28(3) 54-58, 2006. (article provided in Lesson 1 folder)

2. An excellent collection of research summaries on specificity can be found on the San Diego State Coaching Science Abstracts Journal web page here: http://coachsci.sdsu.edu/csa/vol12/table.htm

10

As discussed previously, the phosphagen system provides energy for very short, explosive efforts like a short sprint (8-10 seconds). Once depleted, it takes time to replenish these stores. Following low intensity exercise, the phosphagen system can be replenished in as little as 2 minutes. Following high intensity exercise, a minimum of 3 minutes is necessary. If rest durations are too short, a continual decline in the capacity of this system should be expected, with a resultant decrease in performance of successive intervals. When training for maximal short sprint performance (i.e., 50-100 yard), a minimum of 5 minutes of recovery should be provided between sprints to ensure adequate recovery. The same is true concerning rest between sets for a strength training program. If the goal is to use maximum weights on each successive set, at least 3 minutes rest should be provided between sets to ensure the recovery of the phosphagen system. The anaerobic glycolytic system converts glucose to lactate (lactic acid) and energy. This system does not have quite the same energy turnover rate as the phosphagen system, but it lasts longer (up to 2 minutes). A 400m sprint or ¼ mile run would fall in this energy system. High intensity efforts of 30 seconds to 2 minutes can produce large amount of lactate. Extended recovery periods are necessary if full recovery between bouts is desired (i.e., 10 minutes). The aerobic system has the lowest energy turnover, but it can sustain power output for a long time (hours). Even efforts as short as 2 minutes are using primarily the aerobic system (although anaerobic glycolysis is still engaged enough to produce considerable lactate). Efforts as long as 30-60 minutes are almost entirely aerobic, with a small contribution from anaerobic glycolysis. Training programs should target the appropriate energy system. Sprinters should not be doing large amounts of aerobic system efforts and marathon runners cannot train for the marathon using short sprints.

11

Although adaptations to the cardiorespiratory system contributes to fitness, a large component of fitness is in the individual muscles that are trained. What this means is that only trained muscles will adapt. This is the primary reason that most exercise is mode specific. Only the specific mode that is trained will show significant improvement. Training on the bicycle has some transfer to running, but the transfer is not significant. This is because different muscles are emphasized by the two activities. The degree of transfer from one activity to another is proportional to the degree that the same muscles and energy systems are used. Can you train for a PRT run on the bike, or by swimming? Research has shown that the transfer effects are small, so some improvement may be expected for untrained individuals, but it would be difficult to score well on the run without using a more specific run mode. In water running has been used with success to maintain fitness in injured runners. Because the motion is very similar, many of the same muscles are being used, resulting in enough transfer effects to maintain fitness. Maintaining fitness is different than building fitness and it is doubtful if high levels of run fitness could be built using water running alone.

12

The strength training research literature has demonstrated two additional aspects of training specificity. The graph on the left shows the results of strength testing of two different groups. Both groups trained on an isokinetic dynamometer (ID). The ID allows constant velocity contractions to be performed by keeping the speed of movement constant, while allowing force to vary. In other words, once you set a movement speed, you can push as hard as you want, but the speed will remain constant. One group trained at 96 degrees per second (slow speed), the other at 239 degrees per second (fast speed). You can see from the graph on the left that when strength was tested at various speeds, each group improved the most at the speeds at which they trained. The graph on the right demonstrates joint angle specificity. In this case, each group trained their elbow flexors (biceps) with isometric contractions at a specific joint angle. Again, after testing strength at different joint angles, you can see from the data that each group improved more at the joint angle that they used in training. Reference: Training induced alterations in the in vivo force velocity relationship of human muscle, Caiozzo, VJ, Peerrine, JJ, Edgerton, VR., Journal of Applied Physiology, 51, 752, 1981. Myoelectrical and mechanical changes linked to length specificity during isometric training, Thepaut-Mathieu, C., Van Hoecke, J., and Maton, B., Journal of Applied Physiology, 64, 1502, 1988.

13

This chart discusses training specificity for some of the components of physical fitness. Skill: Skill is the application of coordinated muscle actions. Examples are hand-eye coordination, balance, accuracy, and smooth movements. Coordination of movement is very mode specific and transfer effects are almost non-existent. Practicing free throws with a basketball will not help a baseball player with pitching accuracy. Skills must be trained very specifically for any improvement to occur. Power: Power is the application of force over a short duration. Power is sometimes described as explosiveness. Accelerating off the line for a football player, a vertical jump, or a power clean are all examples of power activities. Because power is determined by a combination of strength and skill, it is very mode specific. Strength training alone can help with power production, but practicing the actual skill is necessary due to the skill component. Strength: Strength is the ability to produce force. Strength transfer from one movement or activity to another is proportional to the extent that the same muscles are used. Therefore there can be significant transfer if the movements are similar. A heavy tire flip and a deadlift both involve hip and knee extension. Training the deadlift would be expected to help with this task. Muscular endurance: Muscular endurance is the ability to perform repeated repetitions of a particular movement (i.e., situps, pushups). Like strength, there is some transfer to similar movements but little transfer to strength. Doing pushups would do little for increasing your bench press strength. Maximum aerobic capacity: Maximum aerobic capacity refers to the top end work rate in the aerobic metabolic system. This would correspond to the maximum work rate (i.e., run pace) that you can hold for 4-9 minutes. The PRT run is very close to this level. Most people would run the PRT at more than 95% of their maximum aerobic capacity. Training at this intensity provides a strong stimulus for increases in cardiac stroke volume, or the amount of blood the heart can pump with each beat. It also results in significant changes in the specific muscles used in training. The cardiovascular adaptation (stroke volume) may provide some transfer to other exercise modes, but total transfer is limited by the muscles trained. Aerobic endurance: Aerobic endurance is the ability to continue low intensity aerobic activity for an extended period of time (i.e., long run). This ability is limited primarily by metabolic fatigue in the muscles, so it is very mode specific. Flexibility: Flexibility is the ability to move a muscle/joint through a full range of motion. This fitness ability is completely mode specific. Stretching affects only those muscles that are stretched.

14

The acute affect of a training session is reduced performance due to fatigue. If adequate recovery is provided, the body overcompensates, resulting in improved performance. This simple phenomenon is called the overload-recovery cycle, or progressive overload. In order to continue to improve over time, the training stimulus needs to provide progressively more overload, with adequate recovery. Overload can be achieved by increasing either the intensity, volume or frequency of training sessions (or a combination). Done correctly, progressive overload leads to a steady increase in average fitness Reference: Avoiding Overtraining: Monitoring of recovery in endurance athletes, Lundin, P., National Strength and Conditioning Journal Vol 7 (6), 1985, Pg-41-41. (article provided in Lesson 1 folder)

15

If the overload or stress is too great, or inadequate recovery is provided, we get a decline in fitness, rather than an increase. This is called overtraining. If the training stimulus (or stress) is inadequate, there is no overcompensation response, and therefore no gain in fitness. Reference: Avoiding Overtraining: Monitoring of recovery in endurance athletes, Lundin, P., National Strength and Conditioning Journal Vol 7 (6), 1985, Pg-41-41. (article provided in Lesson 1 instructor resources folder)

16

The adaptations that occur from training programs begin to disappear once the training program is ended. This effect is called reversibility or detraining. The time course and magnitude of detraining depends on many factors. In general, the more highly trained the athlete, the greater the magnitude of detraining . A reduced training volume, rather than total cessation of training, has been shown to prevent detraining for a significant period of time. If an athlete is forced to reduce training volume significantly, maintaining intensity, rather than volume (for strength and aerobic/endurance) seems to be most important.

•The time course of detraining of strength training adaptations has not been thoroughly studied. The research shows different timelines depending on the strength training program employed and the training level of the individuals studied. In general, strength starts to decline after 3-4 weeks. Beyond 4 weeks, the strength loss can be considerable. •Endurance detraining begins in as little as 2 weeks. The initial declines in endurance are small, but large declines occur after 3 months. •Flexibility decreases rapidly after cessatation of a stretching program. Significant declines in flexibility can occur in as little as 7 days. •Skills are fairly resilient to detraining. Skills decay slowly and can be brought back to near previous levels within a short period of time.

Reference: Detraining, its effects on endurance and strength, Strength and Conditioning Journal, Feb. 1994, pg 22-28. (article provided in Lesson 1 instructor resources folder)

17

18

The Navy Operational Fitness and Fueling Series (NOFFS) is a complete fitness and nutrition program designed by Athletes Performance Incorporated, to address injury prevention and basic operational performance among Sailors. The program consists of warm ups, core work, strength training, flexibility and cardiovascular training. It is designed to be performed with minimal equipment (dumbbells, resistance bands and bodyweight). NOFFS kits come with resistance bands and laminated copies of all of the workouts. The workouts are presented as levels, with different options for large deck ships, small ships and submarines. The minimal equipment workouts, including all stretching and cardiovascular workouts, can be performed in a small 4’ X 10’ space. Also provided is easy to understand nutritional guidance. Navyfitness.com has the complete program, along with exercise videos and ordering information for NOFFS kits. Keep in mind that while NOFFS is an excellent program, it is also a generic program and may not address the specific demands of your situation. NOFFS is being taught and used an many entry level Navy schools and is the primary fitness program taught to all Navy Command Fitness Leaders.

19

The Human Performance Resource Center (HPRC), located at: http://hprc-online.org/, provides information on physical fitness, environmental physiology, nutrition, dietary supplements, psychology and medical concerns. The site is maintained by a panel of subject matter experts from all services.

20

The Navy has subject matter experts (SME) in a wide variety of fields that can help with operational fitness and physiology concerns. These SMEs are available to answer you questions and provide information and guidance. Aviation: The Naval Aerospace Medical Institue n Pensacola Florida specializes in aviation medicine. The Naval Survival Training Institute in Pensacola Florida specializes in aviation physiology (hypoxia, G-Induced Loss of Consiciousness, Fatigue, Swimming, Survival, Spatial Disorientation etc.). Submarine/Diving: The Naval Undersea Medicine Institute in Groton sepacilizes in submarine medicine and diving medicine/physiology. Surface: The Surface Warfare Institute of Medicine in San Diego specializes in issues relating to surface warfare medicine. Special Operations Forces: The Naval Special Operations Medicine Institue in Fort Bragg specializes in special forces medicine. Reserarch: Research in warfighter performance (all platforms and warfare specilties) is conducted at the Naval Health Research Center in San Diego. If you have a question relating to warfighter performance and physiology, chances are that they have an expert who specilzes in that area.

21

More technical information can be found at the Defence Thechnical Information Center website (http://www.dtic.mil/dtic/), which indexes and provides access to all DOD technical reports, including many excellent reports relating to military operational physical fitness. This screenshot shows the results of a search for “Navy SEAL Physical Fitness.” Most reports are available as PDF. DTIC would be an excellent choice for reports that are very military specific. The reports can be very technical. The SME organizations listed on the previous slide would be an excellent resource for understanding the information presented in these reports.

22

PUBMED is an indexing service that provides abstracts (short research summaries) for all biological science and medical journals. PUBMED indexes tens of thousands of journals. Almost any physiology, biological science or medical article published in a peer reviewed scientific journal will be indexed in PUMBED. This screen shot shows the same search “Navy SEAL Physical Fitness.” The difference between DTIC and PUBMED is that DTIC indexes DOD published reports only. To get the full text articles, rather than the abstracts, you can use the library function in Navy Knowledge Online, or use your local library. Most of the articles in PUBMED will be very technical in nature. Again, use the SME organizations previously identified for more information.

23