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

Effect of Instructions 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

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

Grip Strength, Work Capacity and Recovery Relationships between strength, fatigue and work capacity central to occupational rehabilitation questions in paper how important is strength as a component of work capacity how do work capacity and strength affect recovery time

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)

Background Prediction equations for muscular endurance at a given % of max contraction - constants for each muscle group (Sato) results 10-30 % 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

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

Methods Standard body position and instructions Establish pre trial max - isometric isometric - 3 trials 3-5 sec 20-30 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%

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

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

Comparing Isokinetic Strength 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 22-36 (table 1) 3 box sizes 25 - 50 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

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

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

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 recovery 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 isokinetics correlation variable with speed difficult to establish safe %