Week 2: Impact Force Variables and Injury

Question 1

The Leiberman et al., 2010 study hypothesised that footwear may be the cause of injury behind running. Discuss the result.

Answer 1

There was a loss of impact peak when running barefoot for habitual shod runners- more of a mid foot strike.
However, it is not realistic for the majority of people to transition into barefoot running. Removing shoes may displace the load and affect injury risk elsewhere in the body.

Question 2

What percentage of typical shod runners have RFS?

Answer 2

75-80%

Question 3

How does cushioning aim to reduce impact loading?

Answer 3

through changing the material properties of the shoe to reduce the magnitude of the peak impact force and the rate at which it occurs

Question 4

Define: Impact force

Answer 4

An abrupt collision between foot and ground that occurs between 0-50ms of stance and is 1.5-3BW in magnitude.

Question 5

What were the aims and results of the Hreljac et al., (2000) Study?

Answer 5

The study conducted an evaluation of lower extremity overuse injury potential in runners.

No significant difference was found between the injured group and uninjured group in the peak impact force and loading rate.

Significantly higher in the injury group

Question 6

What were the aims and results of the Bennell et al., (2004) study?

Answer 6

The study evaluated ground reaction forces and bone parameters in females with tibial stress fractures.

There was no significant difference between impact phase variables or propulsive phase variables across the injured or uninjured group.

Question 7

What were the aims and results of the Milner et al., (2006) study?

Answer 7

The study examined tibial stress fractures in female runners.

There were higher loading rates for the tibial stress fracture group compared to the uninjured group.

Question 8

What are the limitations of conducting a retrospective study?

Answer 8

There may have been variation within the controlled variables. For example, across all the literature the shoe design in the control group may have differed. There may have also been variation in factors known to influence GRF such as running speed. Additionally, participants may have had altered kinematics post injury or differing responses to injury.

Question 9

What are the aims and results of the Bredewg et al., (2013) study?

Answer 9

A prospective study to look at the GRF in injured and uninjured individuals.

Te baseline variables taken at the start of the study indicated that the injured runners had higher average loading rates compared to the non-injured runners.

Question 10

What are the aims and results of the Davis et al., (2016) study?

Answer 10

A prospective study looking at general injuries in female runners.

There was a significant difference in peak loading rates between individuals who were injured and those who did not incur injury.

significantly higher in those who were injured.

Question 11

What are the aims and results of the Nunns et al., (2016) study?

Answer 11

The study evaluated four biomechanics and anthropometric measures to predict tibial stress fracture in 1065 royal marines.

There was support for looking at the impact phase but did not look at loading rates.

There were higher peak heel pressures under the heel for those who did get injured.

Question 12

Outline the aims and results of Zadpoor and Nikkoyan (2010) systematic literature review.

Answer 12

The review investigate the relationship between lower extremity stress fractures and the ground reaction force.

There were a wide variety of conclusions drawn from each study. However, there was more support for the use of loading rates.

The stress fracture group showed significantly higher vertical LR for a large number of studies

Some studies found no significant difference

LR was a potential mechanism for injury

Question 13

Outline the aims and results for the Van der Worp et al., systematic review

Answer 13

the review investigate whether runners who suffer injuries have higher vertical GRF than those who don’t.

Loading rate was higher in injured cases.

Question 14

Describe the appartatus used in the shore test

Answer 14

A durometer is held vertically against the substrate of interest. The value on the scale is proportional to the amount of indentation of the durometer.

Question 15

Outline the results of the Nigg et al., (1988) running study.

Answer 15

There were no changes in GRF or kinematics with variation of insoles across the two different types of shoe.

Insoles did not provide any form of cushioning.

Question 16

What were the results of the Dixon et al., (2008) military boot study.

Answer 16

There was no significant difference in peak impact force between any condition despite the marked differences in mechanical test findings.

The time of occurrence and peak impact force was significantly later for insole C- the forces remained the same but the change in time also affects the average loading rates.

Insole C has a significantly lower loading rate than the other conditions.

Question 17

Outline the results from the O’Leary et al., (2008) running study.

Answer 17

1. insoles reduced the rate of loading
2. insoles reduced the impact force
3. insoles reduced tibial acceleration

Question 18

Why might differences be seen between biomechanics and mechanical test findings?

Answer 18

Differing footwear conditions across studies

May depend of the type of participant = experience / injury

Insole cushioning is affected by footwear

Adjustments in kinematics

Question 19

What 5 factors were identified by Bobbert et al., (1992) as influential to GRF

Answer 19

1. Variation in stiffness of joints or muscle activation
2. Joint angles
3. Shoe/ surface or insole properties
4. Human heel-pad properties
5. Heel impact velocity (running speed)

Question 20

What did Hamill et al., (2011) discover about strike index?

Answer 20

Participants adjusted from rear foot to mid foot strike when changing from shod running to barefoot running

The change in impact characteristics was due to the change in footfall pattern not midsole thickness.

Impact force was lower in the barefoot condition

The effect from shoe variation is less that originally thought

Question 21

Describe the findings from the Shorten and Mientes study (2011)

Answer 21

GRF is influences by the acceleration of all body segments

Force is applied to the distill foot as well as the heel

An area of the distal foot was in contact with the ground during the impact peak.