Kines 233 Lab 1
T/F Wingate test highly reproducible?
True- reproducible when person is familiar with test (also for sprint cyclists)(training specificity)
Vertical jump calculation
VJ= Jump reach - standing reach
If the coupling time is long (opposite), the involuntary recruitment will be eccentrically expressed, which may?
increase eccentric muscular loading ® ↑ muscle stiffness (beyond that of tendons?)
Muscle fiber type composition is not the only performance influencing factor, what other factors contribute?
neural -biomechanical -biochemical -psychological
Theoretical relationship between muscle fiber characteristics and actual physical performance (study done on weightlifters and muscle fiber type)
the high percentage and large cross-sectional area of fast oxidative fibers in weightlifters are strongly related to performance in both weightlifting and in vertical jump performance
What are some facts about the Wingate Anaerobic Power Test?
• 30-second, maximal-effort cycling test • developed in the Wingate Institute (Israel) • measures short-term anaerobic power output
Why is angular velocity 180 degrees/second?
• EMG evidence à FT motor units (human biceps brachii) were activated at ~ 50% MVC • evidence - glycogen depletion as a marker à preferential recruitment of FT fibers at 50% MVC • isometric leg extension endurance time at 50% MVC negatively correlated with %FT (1975) • 180 deg/s elicited » 30% of maximal shortening velocity, and ... • a peak torque output of the initial contractions that corresponded to » 50% of maximal isometric torque "thus, ... reasonable to assume a substantial involvement of FT motor units at least during the initial maximal knee extensions"
Mechanical Model of Skeletal Muscle Function
Musculotendinous unit behaves as a contractile component in (muscle fiber) parallel with one elastic component (muscle membrane) and series with another elastic component (tendons)
Anaerobic step test equation / steps.
Absolute power= BW (N) x Step Height (m) (.40) x # of steps in 1 min x 1.33 / 60seconds = (Answer in Watts) Relative = Absolute / Kg = W x Kg
Overview of equation for Peak power
- do equation to find peak power then convert to watts for relative and absolute
How many afferent fibers and motor fibers does it contain?
-2 sensory afferent fibers and 1 motor efferent fiber innervate the spindles
The decline in power may be used to evaluate?
-Anaerobically derive energy from (ATP-CP) / anaerobic glycolysis -short duration (glycolytic capacity not fully exhausted thus cannot be evaluated)
Wingate lab equations / steps. (same thing for 10s test)
-Compute the absolute (kpm/s) and relative (kpm/s/kg) peak (0-5s) and minimum (26- 30s) power scores. -* To obtain this number, the data printout rpms for the correspondign 5s period must be added and divided by 60 -body mass (kg) = • 0.07 = (kp)
What has been reported from EMG activity for pre-stretch vs non pre-stretch?
-EMG activity does not change significantly in muscle that performs an isometric action and is then stretched • EMG activity has been reported to be not significantly different between a prestretch and a non-prestretch muscle action
What does the ergometer measure? and what resistance setting is set ?
-Specific type of work done -7% body mass for untrained (each revolution is 6m)
What causes reflex recruitment of additional motor units? (knee jerk reflex)(myosynaptic stretch reflex)
-Stimulation of the muscle spindles results in reflex contraction of the stretched muscle via a myotatic* reflex, also known as a stretch reflex. -muscle spindle performs both, a sensory and a motor function
T/F Elite athletes posses more elastic energy?
-True elite athletes high forces created = muscle stiffness exceeds tendon stiffness==== tendons deformed more than muscle== more potential energy
What is a muscle spindle and what is its function?
-a long cylindrical fluid-filled connective tissue capsule with tapered ends. ---Stimulated by stretch; provide mechanosensory information to the CNS regarding the length and rate of length change in skeletal muscles
Anaerobic Step Test Procedures Pt 2 (Stepping Technique)
-all-out, single-leg for 60 seconds -arms may be used for balance; cannot be "pumped" vigorously -back must be kept straight with each step (otherwise the step doesn't count) -knee of testing leg must be fully extended; otherwise ... -Time is called every 10 seconds
Anaerobic Step Test Procedures Pt 1 (Equipment used)
-bench (ht = 15.75 in., 0.40 m) -chronometer -scale - measure body mass (kg) -calculator
Lab 3 supplement lab steps and procedures
-establish the maximal handgrip score (MVC, lb.) (dominant hand) of 2 subjects. Compute 50% of the respective scores. -Have the subjects sustain a 90s handgrip effort at 50% MVC during which the respective surface EMG signal from the dominant forearm is recorded. Keep an eye on the dynamometer's force dial throughout the entire effort for the sake of keeping the dial as close as possible to 50% MVC during the entire effort. • Determine the EMG signal amplitude (average RMS) corresponding to the initial an final 5- second periods of the 50% MVC efforts
What occurs during the peak power phase?
-noted within the first few seconds -high score requires a very high contractile effort -supported predominantly by the ATP-CP system
From the resulting power-time data, which variables can be computed?
-peak anaerobic power (highest power output averaged over a 5-s period) -mean anaerobic power (over entire 30-s) -total work -fatigue index = (peak - min.) / max x 100
How many types of specialized fibers do muscle spindles contain?
-two types of specialized fibers with contractile capabilities called intrafusal fibers. (Nuclear bag/Nuclear chain) -contains 1-3 nuclear bag fibers and 3-9 nuclear chain fibers.
Anaerobic Step Test Procedure (Needed measurements)
-weight of the performer (N): body mass (kg) x 9.80665 -number of successful steps in 60 s
Expressing Peak Power in Watts
1 kp/m = 0.163W 1watt = 6.12 kp/m ex. 86.81 kpm/s x 60 sec = 5208.6 kpm/m x 0.163 = 849 W (absolute score) 849 W / 75kg = 11.32 W/kg (relative score)
Sprocket size ratio (pedal cranks to flywheel) is used to convert flywheel rpm to pedal rpm. What is 1 pedal revolution to flywheel revolution?
1 pedal revolution = 3.71 flywheel revolutions 3.71 52 14 = ratio of flywheel to pedal revolutions = 3.71
Vertical Jump lab steps and calculations (before T test)
1. Before performing the Thorstensson Test, all volunteers will be assesed for vertical jump height (VJH) in the VERTEC device. VJH (in) = (jumping reach) - (standing reach) = 3 highest peak torque values (ft-lb) from first 5 efforts / peak torque values (ft-lb) from last 3 efforts Fatigue index first then fiber type %FT = (FI) - 5.20 / 0.9 = % %ST = 100 - (%FT) = %
regression equation
A formula for a line that models a linear relationship between two quantitative variables. y=a+bx If y known= x can be predicted for FT%
What are the steps to operate the biodex?
1. Turn on the dynamometer/computer power by pressing the following four (4) buttons in the specified sequence: 1)main power button (back lower left) 2) lower green button (back lower right) 3) computer button (upper left aspect of computer) 4) upper green button (back lower right). 2. Follow the on-screen instructions to remove any attachments. The dynamometer will initialize. 3. Reattach the desired attachment (e.g., knee extension) making sure to line up the "dots" on the attachment and power head axis. 4. Click on the following icons, menus, and submenus in the following order: PATIENT OPEN KINES 233 NEW PROTOCOL ISOKINETIC UNILATERAL KNEE (extension/flexion) CON/CON: TEST: 180/300 5. Select side (left or right). 6. Clear (ROM) limits. 7. Set Away and Toward (ROM) limits. 8. Calibrate Position. 9. Establish Limb Weight. Manually fully extend the subject's test leg. Press the black "Hold / Resume" button on the motor head unit while holding the leg in position Set Limb Weight. 10. Continue. 11. Run test - Green Start Arrow. 12. Analyze Curves. To run a new test, you must repeat all of the above from the beginning.
What are the steps for Thorstensson testing?
1. had subjects perform Thorstensson test 2. established their fatigue index 3. assessed %FT (biopsy) of same subjects 4. developed a regression equation to predict obtained %FT (biopsy) from recorded fatigue index (% decline in peak torque)
How many gamma motor neurons does a myotatic reflex contain?
6
How do you calculate a subjects mass based on mass?
7% of riders mass - Ex (5.25 kg/0.07 = 75kg)
List the steps of the myotatic stretch reflex (muscle spindle reflex)
A stimulus (1) is transmitted to the CNS via the afferent neuron (2). In the CNS, the afferent neuron bifurcates (3) (in gray matter) and synapses with an alpha motor neuron (4a) and an inter-neuron. ! The alpha motor neuron (4a) leads to contraction (5) of the agonist (quadriceps). ! The efferent fiber (4b) that synapses with the inter-neuron inhibits the excitation of the antagonist (hamstrings) (reciprocal inhibition)
Muscle Fiber type distribution on different athletes
Dependent on sport and muscles used The VL has a greater %ST fibers in aerobic athletes who primarily use the legs for their activity (e.g., runners). Athletes whose sport requires endurance of the upper body (e.g., kayakers) possess a greater %ST fibers in the deltoid.
How do you calculate fatigue index?
FI= (Peak power - Minimum power) / Peak power x 100 (Peak = first 5 sec) (Min= last 5 sec)
T/F To obtain the revolutions completed within any time period (e.g., 5 s), the data printout rpms for each corresponding second must be added and then divided by 30?
False - it should be divided by 60
T/F There is no correlation between fatiguability and proportion of FT fibers during Thorstensson test?
False- There is a positive correlation between fatigability (with rapid maximal voluntary isokinetic contractions) and proportion of fast twitch (FT) fibers in the contracting muscle
Rate of decline in power output is dictated by what?
Fatigue index score
Handgrip Dynamometry lab 4 Steps and procedures
Handgrip Dynamometry 1. After adequate practice, establish the maximal handgrip score (MVC, lb.) (dominant hand) of 3 subjects. Compute 50% of the respective scores. 2. Have the subjects sustain a 90s handgrip effort at 50% MVC during which the respective surface EMG signal from the dominant forearm is recorded. Keep an eye on the dynamometer's force dial throughout the entire effort for the sake of keeping the dial as close as possible to 50% MVC during the entire effort. 3. Determine the EMG signal MedianF (Hz) corresponding to the initial an final 5s periods of the 50% MVC efforts
MAKE SURE TO LOOK AT LABS DONE IN THIS SECTION AND UNDERSTAND EVERY STEP!!!!
I DONT WANT TOO BUT I WILL
Surface EMG Signal Frequency During Fatiguing Efforts (Lab 4 ) steps and procedures
Isokinetic Knee Extensions 1. Setup the Biopac wired EMG unit and software as necessary for surface EMG recording. 2. For each subject collect the surface EMG from the dominant vastus lateralis during the performance of the Thorstensson test. 3. Write the initial and final torque values from the subjects' Thorstensson Tests in the data tables shown below. Compute the subjects' fatigue index 4. Use the Acqknowledge software to determine the MedianF (Hz) of the initial and final 5s periods of the recorded EMG signals and compute its percent decline (%Decline MedianF).
Anaerobic Step Test Mean Anaerobic Power Computation
MAP (W) = [Force (N)] • [0.40 m • # of steps] • [1.33*] / 60 s (In Watts)
What is the main contributor to ATP regeneration (45-49%)?
Main contributor= glycolytic system Contribution of phosphocreatine and aerobic metabolism
Computation of peak power equation
Peak Power = F x D / T (FxD= Work)(Work/ Time = Peak Power) F= Resistance on rider based on body mass (1kp = weight force by mass of 1kg to gravity)(weight basket = 1kg) (4.25 kg + 1 kg= 5.25 kg ====== 5.25 kp) D= Distance in 5 s (# of pedal revolutions) T= 5s
Pushup lab steps and calculations
Power (W) (0-20s) = BW (N) x distance covered (m) x reps x 1.33) ÷ 20 s = 2. Compute your fatigue index based on the mean absolute power scores (kpm/s) of the first and last set. Write the result in the table presented above. Fatigue Index (%) = (first) - (last) / (first) • 100
More in depth for the mechanical model of SKM Function
Primary source of Force concentric action= contractile component (actin, myosin, crossbridge) -Series Elastic component= stretched stores elastic energy increases force production - Parallel elastic component (epi,peri,endomysium, sarcolemma) passive force with unstimulated muscle stretch
Supplemental activity Assessment of the Surface EMG Signal Amplitude / % MVC (Wyatt) Station 1
Setup the Biopac wired EMG unit and software for surface EMG recording. • Record the surface EMG (from the right biceps brachii (barbell curls) and/or right vastus lateralis (back squats)) during 4 incremental sets (5 reps/set). Increse the weight per set by 5 lb. and 10 lb. in the curling and squat sets, respectively. • For each subject compare the concentric EMG signal amplitude (average RMS) among the incremental sets. Used the electrogonimeter signal to establish the concenctric and eccentric phase of each repetition. • Was there a "visual" correlation between the concentric average RMS signal amplitudes and the corresponding loads used?
What is coupling time?
The length of the ammortization phase
What does the 1.33 mean in the Mean Anaerobic Power equation?
The negative work done during the eccentric portion of each step is estimated to be one third (33%) of the corresponding positive work. Hence, the total work accomplished (positive plus negative) is equal to the positive work times 1.33.
What test can be a useful field test to provide a non-invasive indicator of muscle fiber characteristics?
The vertical jump (a simple test for lower-body power) may be a useful field test to provide a non-invasive indicator of muscle fiber characteristics. VJ= Jump reach - standing reach
T/F In the 60s Anaerobic power-time curve(s) a fatigue index may be computed and used to evaluate improvements of (longer-lasting) "anaerobic" endurance during any given period of training?
True
T/F Power score for each 6 10s period can be computed by recording the number of steps every 10s ?
True
In order for the involuntary recruitment to be concentrically expressed what needs to occur?
a short eccentric-concentric coupling time is needed (associated with a short eccentric ROM and intense eccentric breaking force)
Thorstensson Test (Purpose and Outcome)
• Purpose: investigate the development of fatigue in human skeletal muscle with repeated fast maximal isokinetic actions, and its relation to fiber composition of the contracting muscle • Outcome: non-invasive estimation of muscle fiber type composition (knee extensors
What is Stretch-Shortening Cycle (SSC) and the Restitution of Elastic Energy?
• SSC muscle actions: those in which an active prestretch is followed by active shortening • natural part of most movements • typical pattern observed in walking, running, jumping (how about in throwing, kicking, cycling?) • active prestretch (when properly done) promotes potentiation of ensuing concentric actionThe
Restitution of Elastic Energy / EMG-to-VJH ratios (Lab)
• Setup the Biopac wired EMG unit and software as necessary for surface EMG recording during vertical jumping. • Setup the PROBOTICS Switch Mat. • After proper calibration, attach the Biopac electrogoniometer to the lateral aspect of the subjects left knee. • Collect the left knee joint angle along with the surface EMG from the right vastus lateralis during 6 vertical jump efforts (3 SJs and 3 CMJs) done on the PROBOTICS Switch Mat (Just Jump mode). • Record the vertical jump height (VJH) of all jumping efforts. • Use the knee joint angle data to determine the concentric EMG signal amplitude (average RMS) of the corresponding vertical jump efforts. • Compute the concentric EMG-to-VJH ratios (arbitrary units) for all jumping efforts.
Supplemental Lab Handgrip dynamometry (Frank)
• Setup the Biopac wired EMG unit and software for surface EMG recording during Handgrip Dynamometry. • After adequate practice, establish the maximal handgrip score (MVC) (lb.) (dominant hand) and the corresponding forearm's maximal RMS score (mV). Make sure the MVC effort lasts at least 5 seconds. In addition, compute the handgrip scores equivalent to 30%, 50%, and 70% of the maximal handgrip score (MVC). • After an adequate rest, record the forearm's surface EMG while holding steadily for 5 seconds the dynamonter's needle at 30%, 50%, and 70% of the maximal handgrip score. Compute the respective average RMS scofres (mV). Try to rest at least 90 seconds between each effort. • For each submaximal effort, compute the % MVC of the corresponding RMS signals.
During CMJ, DJ, the eccentric breaking force (if strong enough!) will?
• during CMJ, DJ, the eccentric breaking force (if strong enough!) will increase muscle stiffness (stress:strain ratio) beyond that of the tendons Storing and Restitution of Elastic -Stiffer muscles stretch tendons and load them with potential, elastic energy ® performance!
During SJ, muscle tension needed to maintain the initial (stretched), isometric position is low
• during SJ, muscle tension needed to maintain the initial (stretched), isometric position is low ♢ tendons do not stretch (no energy stored) ♢ muscle is responsible for increase force generation
What is the relevance of the stretch (myotatic) reflex?
• during SSC muscle actions, when a muscle is actively stretched, the resulting stretch reflex may amplify concentric force output • the voluntary recruitment (and its resulting force) will be supplemented by the involuntary recruitment triggered by the stretch reflex loop
Thorstensson Test (application if fiber type is known)
• establish physiological aptitude, potential for success → prescription of athletic events • implementation of conditioning programs aimed to improve a deficiency • can help explain individual differences in performance and response to training (what training can and cannot do)
Elastic energy stored in actin myosin cross bridges? What is needed?
• if elastic energy was stored during a prestretch in the actin-myosin cross-bridges, it would be lost as soon as these detached • Average attachment time = 30ms , thus, use of elastic energy stored in this fashion would require a very fast eccentric-concentric transition time
Facts about storing and restitution of elastic energy?
• magnitude of stored energy is proportional to the applied force and the induced deformation • muscle and tendon are arranged in series à subjected to same (tensile) force when stretched • distribution of the stored energy between them is a function of their deformation • deformation is a function of their stiffness
Anaerobic step test (Facts Pt 1)
• measures the mean anaerobic power output over a minute of sustained exercise • better indicator of "anaerobic capacity" due to its longer-lasting dependency on "anaerobic" energy systems (ATP-CP + glycolysis) • glycolysis is the primary contributor to the ATP regeneration chore • during maximal efforts lasting one minute and involving large muscle groups, the energetic support seems to be 65-70% anaerobic and 30-35% aerobic
How do you compute Fatigue index for the Thorstensson test?
• out of the first 5 spikes, take the average of the 3 highest à this represents "maximal strength" • take the average of the final 3 spikes à this represents "final strength" • subtract "final strength" from "maximal strength" and divide the result by "maximal strength." • multiply the resultant number by 100 • this last value represents fatigue index (i.e., % decline in peak torque
Anaerobic Step Test (Facts Pt2)
• power scores from the AST have been shown to improve as a result of intense anaerobic training • test may be used as a tool to evaluate the effect of such training on anaerobic endurance (at least during an intense and sustained 1-min effort) • the power scores from the AST strongly correlate to lean body mass (r = 0.87); moderately to dominant leg strength (r = 0.61)
Peak power computation example
• resistance (F) against flywheel = 5.25 kp (subject's mass = 75kg) • duration of peak power phase = 5s • how much horizontal distance (D) was covered in the 5s phase? • assuming the completion of 13.78 pedal revolutions in 5s ... • horizontal D = 13.78 rev x 6m/rev = 82.68 m (rev x 6 meters per rev) -work = 5.25 kp x 82.68 m = 434.07 kpm -peak power = 434.07 kpm ÷ 5s = 86.81 kpm/s
What occurs because of the storing and restitution of Elastic Energy?
• restitution of stored (potential) elastic energy (i.e., elastic recoil of tensed muscle-tendon unit) results in: ♢ strength of subsequent concentric (Å) action (i.e., very forceful, ballistic shortening) ♢ work, power of Å action ♢ ¯ metabolic, recruitment requirements for a given level of increase muscular tension ex., muscles, tendons, and ligaments as springs in series during running, jumping, etc.
Mechanisms Causing Greater Force During Stretch Shortening Cycle Performances?
• storing (and restitution) of elastic energy: ♢ myosin cross-bridges ♢ tendons ♢ other connective tissues • reflex recruitment of additional motor units
What is the relationship between muscle fiber characteristics and physical performance?
• strength/power athletes have higher %FT fibers than aerobic athletes • the cross-sectional area of FT fibers is larger in weightlifters and strength athletes than in sedentary individuals or aerobic athletes (selective hypertrophy) • based on the structure-function relationship that underlies physiology, a strong relationship would be expected between fiber type percentage and performance variables
Thorstensson Test (Methods)
• subject performs 50 consecutive, maximal effort knee extensions (~ 0.5 sec. in Original Study) • passive knee flexion (~ 0.7 seconds in OS) • an average of 50 extensions performed per min. • peak torque produced by each knee extension effort is recorded • angular velocity = 180 deg/s (why?)
Since the enhancement of force from a prestretch lasts longer than 30ms, other mechanism to store elastic energy must also be present. What are the other mechanisms?
• the majority of elastic energy is probably stored in within connective tissues -Tendons (primary source)
Storage and Restitution of Elastic energy Facts
• the stiffness of a tendon is constant while the stiffness of a muscle is variable • in response to high eccentric forces, muscle stiffness can exceed tendon stiffness ♢muscle resists stretching; tendon is stretched • in elite athletes, the storing of elastic energy is primarily in the tendons
A very forceful ecc.-con. transition (CMJ, DJ) will
♢ Increase the magnitude of eccentric "breaking" force ♢ Increase the extent of muscle recruitment just prior to added force generation (ecc.-con. carry-over!) -Increase muscular force output independent of that resulting from elastic E restitution! -Greater concentric force for a given level of recruitment during CMJ, DJ
