1. Strength Testing; variability and relevance
Readings -
Matheson - Effects of instructions on isokinetic trunk strength variability, reliability absolute value and predictive value
Garg - A comparison of isokinetic lifting strength
Wolf - relationships among grip strength work capacity and recovery
OUTLINE
Summaries of above findings and discussions
Complete knowledge of methods and results not required

2. Effect of Instructions: (Matheson)
Previous discussions emphasized the need for standardized protocol
consistent instructions important
Matheson paper supports this tenet
asks - what type of instructions produce the best results?
Optimize reliability, validity
Hypothesize
high demand instruction
decrease variability
increase peak torque
produce stronger correlation with performance capacity
than uniform instructions asking subject to put in a consistent effort

3. Instructions - Discussion
With high demand instructions
Found a reduction in performance variability
Table 2 and 3 % coefficient of variation - four trials each speed
less variability at slower speeds
peak torque - fig 1,2 tables 3 and 4
higher in high instruction group
groups affected similarly by changes in velocity
Predictive ability - two heights
separate comparisons table 6-9
significant correlation's found in high demand instruction set
not found in low demand instruction set

4. Psychological Factors
Classic experiments - arm strength
normal conditions
immediately after loud noise
while subject was screaming loudly
influence of alcohol and amphetamines
hypnosis
observed increased strength - most with hypnosis
theorized temporary modification in CNS - argued most people - neural inhibition (protective reflex)
reduced inhibition
highly trained athletes
arousal - unexplainable feats
early phase of strength training

5. Comparing Isokinetic Strength (Garg)
Goal of research
determine effects of speed of lifting and box size on isokinetic strength
compare isokinetic with
static lifting strength
psychophysically determined MAW
9 male college students - range in age (table 1)
3 box sizes cm wide
lift floor to bench
open technique - subjects choice **
rate .2 /min (every 5 minutes) - 1 hr
static strength measured at origin of lift
iso kinetic - 3 speeds
RPE for all lifts - low back

6. Results Progressive decline in mean and peak isokinetic strength
with inc speed and inc box width
speed had greater impact than width
* high speed lifting perceived to be less stressful
RPE 10.7 (fast) vs 12.7 (slow)
static strength and MAW higher correlation with mean than peak isokinetic strength
high speed - mean isokinetic - within 6% of MAW
low speed - mean - equal to mean static strength

7. Recommendations
recommend - both speed of lifting and box width should be controlled carefully
job specific simulation with isokin
using MAW and Static strength testing
* SST results in higher allowable limits
*MAW - effectiveness not as well documented
avoid isokinetics - complex relationships with persons safe max

8. Grip Strength, Work Capacity and Recovery
Wolf
Relationships between strength, fatigue and work capacity central to occupational rehabilitation
strength and endurance correlation exceeds .90
endurance tests - % of body weight
strength test often one rep max (isotonic) ; not always appropriate
1 RM= (weight) / [1- (RM * .02)]
questions in paper
how important is strength as a component of work capacity
how do work capacity and strength affect recovery time

9. Relationships - Background
Capacity to sustain work activity
inversely related to power required
exponential decrease in endurance, as demand approaches max
after injury - loss of power - loss of capacity
rest from injury - often increases impact - muscular de-conditioning
Rehab
strengthen and condition
difficult to establish and define dose of intervention
goal is to accelerate rate of rehab and shorten treatment time( ref 5-7)

10. Background
Prediction equations for muscular endurance at a given % of max contraction - constants for each muscle group (Sato)
results % decline in strength
longer bout, lower recovery strength
Fatigue - theory
short - high intensity exercise - metabolic inhibition
longer duration - non- metabolic
at level of E-C coupling - K+ ?
Relevance of isometric evaluation
low - due to low prevalence of isometric activity

11. Relationships Research goals address 40 healthy subjects - 1/2 male
develop technology necessary to support a treatment strategy
dose of exercise is able to be closely tied to expected levels of recovery
address
expected work duration
work capacity
recovery rates
40 healthy subjects - 1/2 male
repetitive gripping task
25, 50 and 75 % of max
1 sec reps until fatigue
measure isometric grip strength 1, 5 10 and 20 min of recovery

12. Methods Standard body position and instructions
Establish pre trial max - isometric
isometric - 3 trials 3-5 sec sec interval
5 min rest
evaluate isotonic strength
LIDO - isotonic - progressive protocol
complete ROM in less than 1 sec
inc resistance - repeat to fatigue
Test - based on isotonic results
repetitive gripping to fatigue
75% and 50% of isotonic max
then 25% for twice as long as 50%

13. Evaluation After final trial - re-evaluate isometric grip strength
average of three trials
immediate, 1, 5 , 10 and 20 min recovery
Results
correlation isometric / isotonic strength
no correlation between isometric or isotonic strength and duration of work at either 75 or 50 %
significant relationships between isotonic strength and work capacity
strength more important a predictor of capacity at 75 % level - than duration

14. Recovery No significant gender differences
either recovery time or % at time points
table III and fig 1
Recovery rate and time to recovery
subjects categorized - time to 100%
significant differences in degree of recovery Fig 2
no differences in rate
similar slope, different starting points - degree of loss of strength predictor of length of recovery
Standards - avg 20% decline in strength with protocol - 20 min recovery
variation - abnormal - intervention
standards - tables 4 and 5

15. Conclusions on Types of Strength testing
High demand instructions(isokin)
Reduce variability with high demand instructions
higher correlation to isotonic
better predictive ability for capacity
isokinetics
correlation variable with speed
difficult to establish safe %
recovery from fatigue - FCA
duration of work difficult to correlate to either isotonic or isometric strength
work capacity correlates better to isotonic strength than isometric
recovery rates similar between genders and degree of strength loss
useful in diagnosis