T1 Phys - Topic 14 - Intro to Exercise Physiology Apr 2020 PDF

Module #14 – Introduction to Exercise Physiology Energy Systems ‐ Review    ATP is split into ADP + Pi + energy – the energy is used to power cell functions to use the ATP again, you have to reform it (ADP + Pi + energy = ATP) cells reform ATP by one of 3 metabolic pathways: 1) from phosphocreati...

Module #14 – Introduction to Exercise Physiology Energy Systems ‐ Review    ATP is split into ADP + Pi + energy – the energy is used to power cell functions to use the ATP again, you have to reform it (ADP + Pi + energy = ATP) cells reform ATP by one of 3 metabolic pathways: 1) from phosphocreatine (PCr) 2) anaerobic cellular respiration 3) aerobic cellular respiration    the PCr system is unique to muscle fibres all cells can produce ATP using anaerobic and aerobic pathways the energy systems work together to generate ATP but one system is usually dominant based on the demand (e.g. sprinting vs. walking) 1) Phosphocreatine System (a.k.a. ATP‐PCr, creatine phosphate, anaerobic alactic)  PCr is a molecule that stores high amounts of energy in its chemical bonds  when PCr is split by an enzyme, the energy released is used to reform ATP  happens very fast therefore PCr is the first energy pathway used  provides energy for 3 – 15 seconds of maximal contraction  no oxygen needed, no lactic acid produced 2) Anaerobic Glycolysis  when muscle activity continues and PCr is depleted, glucose is used to make ATP  cells break down glycogen stored in their cytoplasm/sarcoplasm or glucose from the blood and the energy released in breaking them down is used to reform ATP  making ATP from glucose occurs in the cell cytoplasm and is called glycolysis  one molecule of glucose is broken into 2 molecules of pyruvic acid and 2‐3 ATP  if oxygen is present, pyruvic acid enters the mitochondria where it undergoes and series of reactions (that require oxygen) called aerobic cellular respiration  during heavy exercise/demand, not enough oxygen is available (hence ‘anaerobic’)  in the absence of oxygen, pyruvic acid does not go into the mitochondria but is instead converted into lactic acid/lactate  lactic acid diffuses out of the cell into the blood where it is used by other cells or converted back into glucose in the liver  no oxygen required and producing lactic acid = anaerobic lactic  capable of supplying energy for 30‐40 seconds Lactic Acid/Lactate     a metabolic by‐product of anaerobic metabolism at lower levels of activity, lactate does not accumulate it is also converted back into to glucose/glycogen in the liver (the Cori cycle) lactic acid has a ½ life of 15‐25 minutes and is cleared in (at most) a matter of hours p.256 3) Aerobic Cellular Respiration  this pathway is active when you are able to get oxygen in to the cells (e.g. at rest or at low‐moderate intensity exercise)  oxygen is delivered by myoglobin or from oxygen diffusing from the blood  in the presence of oxygen, pyruvic acid enters the mitochondria and in a series of reactions (that use oxygen), produces much more ATP (much more than glycolysis)  carbohydrates, fats, and proteins can be used in this process to make ATP  carbohydrates yield relatively little ATP  fats yield a lot of ATP  proteins aren’t used readily (often not even included)  at rest, cells of the body use aerobic metabolism to generate their ATP  in activities that last longer than 10 minutes, most (90%) of the ATP generated comes from the aerobic system p.257 Definitions Physical Exercise    a single acute bout of activity that requires energy expenditure above resting levels typically planned and structured designed to improve or maintain one or more components of physical fitness Acute Exercise Response  how the body responds to a single bout of exercise Training Adaptations  how the body responds over time to the stress of repeated bouts of exercise Repetitions (‘Reps’)  the number of times a particular movement is repeated Sets  a number of repetitions grouped together “...to failure.”  performing a given exercise until you cannot perform another repetition with proper technique p.258 Muscular Strength    the ability contractile tissue to generate tension (contract) often viewed in the context of the maximum force that can be generated by a muscle or muscle group with one contraction functional strength is the ability of the neuromuscular system to generate and control forces during functional activities Muscular Endurance  the ability to produce low‐intensity repeated activities over prolonged time frames Flexibility  the ability of a joint or series of joints to move through a full range of motion (ROM) without injury Exercise Responses Basic Responses to Acute Exercise (in the apparently healthy person)     heart rate: during exercise, it increases directly in proportion to the intensity of the exercise (there is a natural limit) blood pressure: systolic increases, diastolic doesn’t change appreciably (note: significant increases in blood pressure are seen with holding the breath on exertion (e.g. during resistance exercise)) blood flow: increases to the working structures, and is decreased to viscera ventilation: increases during exercise Training Adaptations (in the apparently healthy person)  muscular strength       muscular endurance      initial strength gains are due primarily to neural adaptation (often rapid – within 4‐8 weeks) neural adaptation: motor learning, increased motor unit recruitment, increased rate and synchronization of firing subsequent increases are due primarily to hypertrophy hypertrophy comes after the initial gains and is from increased protein content (i.e. actin, myosin) tendons, ligaments get stronger increased muscle capillarization increase in number and size of mitochondria increased energy substrate storage (PCr, fats, glycogen) tendons, ligaments get stronger flexibility/range of motion (ROM)   ongoing increased flexibility/range of motion improperly applied, there is a risk of hypermobility p.259 Parameters of Exercise FITT     frequency – how often the exercise is performed per day or per week intensity – how hard someone is working time – how long the activity is performed type – what is the activity being performed Frequency       appropriate frequency depends on the goal, mode of exercise (strength training, aerobic etc.), and the intensity e.g.: post surgical muscle setting (to offset atrophy, maintain neural pathways) may require low weight, low repetition isometric exercises multiple times per day e.g.: standard weight, standard repetition resistance exercises (to improve strength) usually require a day of recovery in between e.g.: maintenance of strength may require higher intensity exercise with 2‐3 days recovery in between e.g.: performance‐related cardiovascular training: higher % HRmax, 3‐5x per week e.g.: health‐related cardiovascular fitness: 60% HRmax, daily (one session or spread out over 10 minute bouts) Intensity    muscle strength training: 6‐12 reps (to failure), 2‐3 sets muscle endurance training: 15‐50 reps (to failure), 3‐5 sets aerobic training: 30 minutes, 60‐80% HRmax Time   how long the program is being done for (weeks – months) note adaptations and goals Type (Mode)   resistance training, balance/proprioception training, aerobic training specifics (e.g. strength, endurance, isometrics, running, swimming, walking...) Rest Interval   the amount of time between sets this ranges from 1‐2 minutes (low intensity exercise) to 4‐5 minutes (high intensity exercise) p.260 Note:   the above numbers reflect guidelines as they apply to apparently healthy people they will change based on patient presentation and your clinical decision‐making processes! p.261 Training Principles      specificity – select the exercise that is best suited to meeting the goal overload – to achieve the goal, you must challenge the system beyond its current level – manipulate FITT recovery – allow sufficient time between exercises (sets and days/week) progression – to achieve the goal, you have to move beyond the adaptation maintenance – once the goal has been achieved, it can be maintained with a reduction of 1/3 – 2/3 frequency as long as the intensity is maintained Detraining    ‘the partial or complete loss of training‐induced adaptations’ adaptations are reversible detraining may occur for many reasons (lack of compliance, injury, illness...) Delayed Onset Muscle Soreness (DOMS)    muscle tenderness, pain on palpation, stiffness after exercise typically starts about 8 hours after, peaks in 24‐48 hours and dissipates in a few days not fully understood but there are theories – the current models include the following factors:  unaccustomed high intensity exercise (especially eccentric exercises) causes damage to the structural proteins in the muscle fibres  inflammatory and immune processes activate  these processes (especially the fluid accumulation) also irritate nerve endings (causing pain) p.262 p.263