ASEP Procedures Recommendation 1: Accurate Assessment of Muscular Strength and Power
Strength and power are fundamental components of performance that are commonly assessed to better understand functional capacity and overall exercise prescription. The validity and reliability of these measurements are essential for every practitioner when implementing proper techniques for collection and analysis of strength and power tests. Through the different modes of exercise, isometric, isotonic and isokinetic in addition to concentric and eccentric, general guidelines on the assessment are utilized to conduct the trial successfully.
Appropriate planning and organization of each assessment and evaluation are crucial to reduce the likelihood of errors and to better understand possible limitations that may occur. Component such as familiarization and specificity are essential to consider when performing all types of assessments and could increase the likelihood for variation among measurements. Another aspect though possessing little data for decreasing the risk of injury, general guides for warm up prior to assessment should be provided to maintain consistency for each participant.
These among many other aspects are important when conducting isometric or static testing. This form of evaluation is performed with no change in muscle length, to primarily assess smaller changes in fiber length and other elastic components. The major advantage of isometric or static assessment is the large variety of devices that are designed to be simpler and quicker to use. This allows for testing large groups of participants and for the estimation of other variables, such as rate of force development and strength throughout the range of motion. The major pitfall with this form of testing is that the isometric strength at one angle has a poor correlation with other joint angles.
Considerations for this evaluation also include the duration of the contraction due to differing rates of maximum force development among individuals. The literature seems to recommend approximately a one second period for transition and about a four to five second period to allow for maximum isometric contraction. Recommendations on intervals between reps and the number of reps state that the use of a 30 to 60 second rest will allow for adequate recovery and performing fewer reps will limit the effects of fatigue.
The next contraction evaluation discussed is isotonic testing, where individuals perform a movement against a fixed mass against gravity, generally on a machine. These tests reported to possess high-testreliability; criticism on the isotonic 1-RM test develops from the perceived notion that muscles perform submaximal contractions, except for the “sticking-point” of the lift. Using multiple sets to build up to a maximum weight lifted can also cause fatigue, standardization of warm up and progression procedures are crucial to create reliable results.
Including bench press, other tests can be administered, such as the vertical jump test. Two types of vertical jump test are squat jump and counter movement jump, which differ in respect to an opposing concentric contraction performed in the counter movement jump, prior to the maximal jump assessment. A high reliability and validity are reported with these evaluations, according to previous literature, with the exception of existing variability pertaining to warm up and practice procedures. In regards to testing specificity, the vertical jump is the primary method and recommendations discuss using three practice trials and when performing multiple attempts to maintain constant arm movement.
The Wingate Anaerobic Cycle Test (WAT) is employed to assess the anaerobic power of the lower body. Measuring five-second intervals to understand peak power in Watts, mean power across all six data points and fatigue percentage, the difference between the highest and lowest measurements. With high-testre-test reliability, the validity of this measurement can be difficult to understand because there is no “Gold Standard” of anaerobic measurement. The resistance that is set for each individual is found through the use of equations using body weight but finding the optimal resistance can be difficult. This procedure is standardized through testing 30-second intervals to find revolutions/second to assess the appropriate resistance for each participant.
The final assessment type is isokinetic testing, is through constant velocity, showing a match between a velocity set by a machine and the movement of the participant. In order to maximize the reliability of this assessment, factors like variable measured, proper positioning and stabilization, and narrowing data for analysis must be considered during assessment. Three specific measurements, peak torque, work and peak power, are the most commonly used variables. Assessing maximum torque in any range of motion, the amount of torque over a certain distance and power establishing work over a certain interval of time, respectively.
Various aspects of this testing must be under careful consideration to maximize the reliability of these measurements. Range of motion, practicing instructions and movements, and the amount of repetitions must be determined based upon the goals of the assessment. When using the dynamometer, the velocity in which the participant moves against or with should be in a random sequence to control for any order effect. Additionally, the bilateral deficit is an important component that may affect torque against similar velocities and seem to have a significant effect on female participant measurements.
Proper calibration of the dynamometer is crucial in limiting both velocity and torque overshoot. Due to the selection of a preset velocity, the limb being tested can display speeds and torque greater than the preset velocity, especially at the end of the acceleration phase. The lever arm attempts to accommodate for these overshoots and spikes by counteracting the velocity with a braking mechanism. The probability of error is increased with this catch-up or braking mechanism of the lever arm and should be considered when analyzing the data. When discussing the relationships between these variables, there is an apparent decrease in overall torque when velocity increases during a concentric contraction. When comparing power and velocity, there seems to be an optimal velocity of approximately 240 degrees per second to maximize power in males, and 180 degrees per second for females.
Multiple devices and methods are incorporated to assess strength and power related variables. Understanding the desired method of assessment will allow for greater reliability and validity of the measurements. Previous understanding of the aspects of each experimental trial provides researchers the opportunity to appropriately standardize all instructions and test specific considerations to achieve optimal data collection and analysis.