Lecture 1

Question 1

Define what is meant by neuromuscular performance?

Answer 1

The maximal output, within the first few seconds of contraction, that an individual can produce

Question 2

What is meant by isometic, isokinetic and isointertial?

Answer 2

Isometric - fixed length
Isokinetic- fixed velocity
Isointertial- fixed mass

Question 3

Define power? and what is the equation for power?

Answer 3

Definition: the rate of doing physical work

Power= Force x velocity

Question 4

Why is power important to athletic performance?

Answer 4

High correlations have been found between peak power output and performance

Jump height and peak power - r=o.8
200m sprint and CMJ peak power- r=-0.69
Throwing performance and peak power during bench press- r=0.71

Question 5

Why is power output important for health?

Answer 5

Power is required for mobility, everyday tasks and independance.

Clarke et al., 2011 found with increasing age, power output decreases. This is considered to contribute to decreased mobility across the groups.

Question 6

Define Force and Torque?

And what equation enables transfer between these variables?

Answer 6

Force is a linear vector quantity that produces an acceleration of a body in the direction of its application

Torque is the rotational equivalent of force

to transfer= T = F x d
where d is the distance between the pivot and the line of the force application

Question 7

What are advantages and disadvantages of isokinetic Dynamometers ?

Answer 7

Advantages: Can measure a number of different joints, and a number of different angles for each joint

Disadvantages: lots of padding and compliance which can alter the angle of measurement up to 20 degrees

Question 8

Describe the Angle-Torque relationship

Answer 8

Torque is measured from a number of different joint angles (or muscle lengths). The results show an inverted U relationship, where people are generally stronger toward to the middle of the range (90 degrees)

Question 9

What are the advantages and disadvantages of isometric measurements of human force/torque output?

Answer 9

Advantages:
easy to use for both participant and investigator
Highly controlled (isometric=no movement) neuromuscular situation for more mechanistic measurements like EMG
High reliability and sensitivity

Disadvantages:
Limited validity- movement is generally more dynamic, acting over a ROM
Measurements have 0 velocity, thus 0 power
Typically involve only a single joint/muscle
Highly specific and only relevant to the joint angle measured

Question 10

What are the similarities and differences of custom built and isokinetic dynomometers?

Answer 10

can both take identical measurements

IKD can do a range of joints, each joint in a range of angles

IKD’s have more padding and limited rigidity; thus significant compliance can occur (20 degrees for IKD vs
4 degrees for custom built (Tsopoulos et al., 2007 and Folland et al., 2014)

Greater resting baseline noise recorded for IKD; thus poor for sensitive movements

Question 11

What is velocity?

Answer 11

The rate at which movement is covered per unit of time

Distance/time in a direction

Question 12

What are ways to measure velocity?

Answer 12

Timing gates
Motion analysis
Laser and radar based movement systems
GPS or accelerometer 
linear replacement transducer

Restrained movement:
Non-motorised treadmill- belt speed
Cycle ergometer

Question 13

Describe the force-velocity relationship? and how power is then intergrated from this relationship?

Answer 13

There is a hyperbolic relationship between force and velocity, that is: force is greatest when velocity is 0 (isometric) and decreases in a curvilinear fashion as velocity increases.

Power can that be calculated for any given force and velocity (P= F x V), where maximum power (V-optimum) occurs at 1/3 max velocity and 1/3 max force

Question 14

What are isovelocity measurements?

Answer 14

Velocity is mechanically regulated in an IKD or ergometer.

The primary outcome variable is torque or power

Question 15

What are the key points when analysing isovelocity data?

Answer 15

1) Despite knee joint moving through ROM, the angle-torque relationship still clearly shows peak torque occuring toward the middle of the range
2) at greater velocities, peak torque decreases

Question 16

What are the two measurement issues at higher isovelocities, using an IKD?

Answer 16

1) short isovelocity period: as velocity increases, the time taken to reach and stabilise at the precise velocity is greater, decreasing the time spent at isovelocity before the deceleration phase
2) Torque overshoot or impact spike from the IKD accelerating up to isovelocity speed increases with increasing isovelocity speed. At very high speeds, impact spike can be greater than peak contraction torque, potentially leading to misinterpretation of the data

Question 17

Using an IKD and a calculated power-velocity relationship doesn’t give use the full picture of the optimum velocity for power. Why is this?

Answer 17

IKD can only measure torque at angular velocities up to 300-400 degrees per second due to short isovelocities periods. Humans can produce movements at velocites around 1000 degrees per second. Thus an IKD cannot reproduce the full story of the power-velocity relationship.

Question 18

What did McCartney et al. (1985) report measuring torque-velocity and power-velocity relationships with cyclists?

Answer 18

They measured torque and power during cycle sprints at 10 different velocities (1 to 190 RPM)

It was shown that as crank velocity goes up, torque output goes down (torque-velocity relationship). However, the findings were more linear in a whole body instead of an isolated muscle.

Following this, optimum crank velocity for power output was then determined as 120 RPM.

Implications: cyclists looking to compete in fixed gear sprinting can set the gear to enable them to cycle at their V-optimum.

Question 19

Describe the basic need to know bits of Isoinertial tasks?

Answer 19

Isoinertial means fixed mass. The resistance to the movement is provided by the inertia of accelerating a fixed mass

It has the highest ecological validity

The scientific understanding is lesser due to the difficulty measuring isoinertial tasks

Question 20

How did Jimenez-Reyes et al. (2014) measure the force-velocity relationship during an isoinertial task? and what were the findings?

Answer 20

Participants performance max jumps with a range of loads on a force place

The force-velocity relationship is similar to both isometric and isokinetic, however, is even more linear. With an Rsquared value of 0.98

Question 21

How did Samozino et al., 2012-14 show that F-V profiles (or slopes) differ between athletes? How did this effect power?

Answer 21

They showed that athletes with a steeper slope were more force dominant, whilst those with less steeper slopes were velocity dominant.

They went on to show that ones F-V slope can influence jumping performance independent of max power.

They concluded by saying ones F-V slope can be compared to the optimum to modify their characteristics and enhance performance.

Question 22

How long does is take to reach peak force during an Isometic MVC? and what implications are there because of this?

Answer 22

≥250 ms

In sport thats a long time:
- Ground contact time during sprinting: 100ms
- ACL rupture occurs ≤ 50ms after ground contact
These events are occurring before peak force is even reached.