Interpretation of Isokinetic Tests
Concepts
• Introduction
• Principle of isokinetics
• Benefits of training through isokinetic
exercise
• Basic terminology
• Reading test results
• Curve analysis
Introduction
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Subjective/objective
Criteria-based protocols
Goals with reproducible data
Biodex advantage!
Principles of isokinetics
• Preset fixed speed
• Accommodating resistance
• Resistance = effort
• Torque measured throughout ROM
• Muscle loaded throughout ROM
• 30 degree overflow
– Strength
– physiological
Functional Test Speeds
• Walking – 233°/s
• Running – 1000°/s – 1200°
• Ankle during running – 540°/s
• Train & test at fast speeds
Benefits of training
• Time rate of tension development (TRTD)
– Upslope of the curve
• Decreased reciprocal innervation time (RIT)
– Time between end of agonist and beginning
of antagonist
• Strengthen musculotendinous junction
– Reduces risk of strains
Basic Terminology/Interpretation
• Peak torque:
– Absolute strength value (1 RM)
• Work:
– Functional value of muscle performance
– Torque over distance
• Power:
– How effective the muscle can perform work
over time
Reading test results
• Is the test reliable and valid?
– Coefficient of variance
– Large values?
– Acceptable CV’s (large/small muscle groups)
Reading test results
• Percent deficit
– Acceptable vs unacceptable
– Negative value?
– Considerations for unilateral athletes?
Reading test results
• Peak torque
– Difficult to assess if used alone
• Peak torque/body weight
– % of torque produced to body weight
– Normative goals - see chart
Reading test results
• Max rep total work
– Better indicator of neuromuscular function
– Muscle must remain recruited during entire
range
– Should occur within first few reps of test
• Work first 1/3..work last 1/3
– Should be more work in first 1/3
– Look for consistency
– Effort
Reading test results
• Work fatigue
– Ratio between first 1/3 and last 1/3
– Should decrease with progress
• Acceleration time
– Time to reach isokinetic speed
• Deceleration time
– From isokinetic speed to zero
– Eccentric control towards end of ROM
Curve analysis
• 4 regions of the curve
– Time rate of torque development (TRTD)
Curve analysis
 Force Decay Rate
T
FDR
ROM
Uninvolved side
FDR
ROM
Involved side
Curve analysis
• Reciprocal innervation time (V vs U)
Injury/condition curves
Chondromalacia patella
Q
H
Q
H
Plica syndrome
Patellar subluxation
ACL Deficiency
Summary Reports
• Absolute/relative
• Bilateral comparisons
• Unilateral comparisons
Speed
Ratio
60°/s
60% - 69%
180°/s
70% - 79%
300°/s
80% - 95%
450°/s
95% - 100%
T:BW Ratio
• General joint integrity
Males
Females
60°/s
110%-115%
60°/s
85% - 95%
180°/s
65% - 75%
180°/s
55% - 65%
300°/s
45% - 55%
300°/s
35% - 45%
450°/s
35% - 40%
450°/s
25% - 30%
Summary
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Correlate to clinical exam
Use pre-established criteria
Valid/reproducible or throw out
Documents muscular performance only