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Curtin University
School of Physiotherapy

Strength and fitness evaluations should not be included in a pre-season assessment!

Proposition for Debate - by Phoebe Cheuk

Contents

Statement of the Topic

Fitness and Strength Evaluations should not be included in a Preseason Assessment

Introduction

In many sports, training for successful competition has become a year-round issue. To assist in better preparation, a competitor's year may be divided into off-season and in-season phases, indicating reduced or increased competition commitments, respectively . The science of training is used for optimisation of training methods and selection of teams for competition in high-performance sport . This paper discusses the affirmative and negative arguments about the use of fitness and strength evaluation in preseason assessment, with reference to the recent literatures.

Strength Evaluation

Athletic strength and power assessment can be used for strength diagnosis or talent identification, to monitor the effects of training interventions and to estimate the relative significance of strength and power to particular pursuits.

Muscular strength

Muscle strength refers to the capacity of a muscle to develop active tension, irrespective of the specific conditions under which tension is measured.

Muscular work and power

Muscular work is the measured as the output of mechanical energy calculated by the force exerted multiplies by the distance through which it is applied. It is appropriate to refer to any measure of strength as power. Power refers to the rate of muscular work output and is expressed as the unit of work per unit time.

Muscular endurance

This relates to the quality of muscle that is the opposite of fatigue. It may be defined as the ability of contracting muscles performs repeated contractions against load or the ability to delay the onset of fatigue. There is no standardized testing protocol for this kind of assessment.

Mode of testing

Currently, isometric, isoinertial and isokinetic dynamometry are employed in assessment. Each form has its supporters and detractors.

Isometric dynamometry
MVC can be developed against an immovable object, without a change in joint angle. Results from isometric protocol have been used as indicators of athletic strength.
Isoinertial / isotonic dynamometry
1 repetition maximum (1RM) can be determined by a weightlifting task on a constant external loading.
Isokinetic dynamometry
Peak torque can be developed by concentric or eccentric contraction of the limb moving at a constant angular velocity.

Fitness Evaluation

Fitness testing is used to enhance athletic performance, setting goals and monitor progress of an athlete or selecting teams for competition. In athletes, physical fitness can be defined as a set of attributes that people have or achieve relating to their ability to perform physical activity and plays an important role on their performance. It is a dynamic, multidimensional, related to heredity, environment and personal interest. Different sports depending on their duration and intensity require different types of specific energy system, strength and skills. Components of physical fitness include cardiorespiratory function, relative leanness, flexibility, muscular strength and endurance.

Cardiorespiratory function

Aerobic fitness test

It can be determined by the maximum oxygen uptake (VO2 max) utilise during an exercise that last for longer than 2 minutes

Anaerobic threshold test

Anaerobic threshold may be defined as the workload just below which steady-state exercise can continue for a prolonged time. It depends on muscle fibre composition, tissue oxygen diffusion and extraction, mitochondrial density, and the balance of the Kerb's cycle. Anaerobic threshold has been extensively used for predicting anaerobic performance.

Anaerobic fitness test

Cycle tests, standing board jump and vertical jump tests are used to determine the anaerobic fitness of the athletes.

Relative leanness

  • Body girth measurement: Thigh, hip, calf and biceps
  • Body density measurement: Hydrostatic weighing
  • Body fat measurement: Skin fold test

Flexibility

Static flexibility
involves the actual range of the muscle and its ability to lengthen or deform, with no relationship to speed of movement
Dynamic flexibility
is the ability to use that range of joint movement by overcoming the resistance to movement during the performance of an activity, at the normal speed of that activity.

Preseason Assessment

Preseason assessments often consist of measurements including muscle strength, flexibility, balance and fitness testing. It is used for:

  • performance monitoring
  • set training regime
  • assess injury potential, and
  • assess the athlete's health status

Information collected is used as a baseline to compare with the result in mid or end of the season testing. For a test to have predictive value it must incorporate some of the dynamic physical characteristics required for a particular sport.

Sports-Specific Assessment

Sport specific assessments are essential to provide information about an athlete's capability of participating in sports and additional information can be gained to improve performance and prevent injuries. The literature of training science prove that the training of general condition, validity for all forms of sports lead to considerable improvements of particular physical parameters.

Affirmative Argument

Reliability and validity of dynamometry testing

Strength and power assessment is a difficult task which include: the fledgling status of research within this area, our limited understanding of the mechanism underpinning strength and power performance and development, and limitations associated with various dynamometry . The debate between proponents and opponents of isokinetic assessment emphasises its apparently high internal and apparently low external validity respectively . No single testing mode in dynamometry is obviously the best or most valid for testing strength and there is no proof that one particular testing mode has any more inferential capacity with regard to functional activity.

Dynamometry currently used can measure power associated with tasks in which either the load or the velocity of movement are held constant. Power can be excellent predictor of measures of peak torque, but give little information about the muscular performance. The 1RM lift used in isoinertial testing is limited to some extent by the experience and the skill of the individual, which in turn compromise the internal validity.

Although isokinetic testing has high test-retest reliability, most of the isokinetic testing was done in the knee flexion and extension task. Therefore, it is impossible to generalise the useful information to other joints. Besides, the movement is often single, isolated joint assessment and loading pattern bear little relationship to most sporting activity. This is especially true as the velocity and loads encountered vary within and between tasks in sports.

Strength testing as an indicator of injury potential

Most of the early studies indicate a correlation between muscle strength and injuries were retrospective. Therefore, the result may be biased as the injury rather than the cause was investigated.

An investigation done to reveal the relationship between strength, flexibility and endurance of shoulder internal and external rotators in swimmers suffered from shoulder impingement. The result showed that no significant relationship was found between pain and strength ratio, but did reveal the negative correlation with endurance ratio. This may suggested that absolute strength measures are not a good indicator of dysfunction.

Lack of correlation between strength measures and athletic performance

There are limited amount of published material correlation strength and power to athletic performance. A low correlation was showed between the isokinetic strength measurements and the functional performance. This work is central to the use of such indices in talent identification.

A large number of studies using all forms of dynamometry in a variety of ways to monitor the effects of resistance training, it is often unknown whether the measurement procedures used best reflect modulations in athletic performance. In dynamometry testing, isometric test mode bears little resemblance to the dynamic nature of most sporting task. Further, isoinertial bears little resemblance to many athletic pursuits in terms of posture, pattern or speed of movement. Isokinetic strength testing has been used as a primary assessment tool to determine a patient's strength, ability to progress to an advanced activity level. However, literature has suggested isolated muscle testing does not give enough information on a patient's functional ability, especially in the sports arena.

Another study included twenty healthy female subjects to compare the isotonic strength 1) for knee extensor in OKC condition, 2) for hip, knee and ankle extensor in a squat exercise (CKC) and a vertical and standing long jump test. Result showed that lower limb extensor CKC muscle strength was more highly related to jumping performance than knee extensor strength in OKC situation.

A significant drop in both maximal concentric and eccentric quadriceps and hamstring torques occurred over a season of amateur ice hockey, in spite of 2 to 3 training season. No relationship was found between the drop in muscle strength and injury rates and performance. There is obvious lack of scientific data relating changes in physical fitness to performance in sports.

Sensitivity of strength measures to the effect of training

Isometric, isoinertial and isokinetic measures have been used to assess the effects of training. Some studies has showed that sprinting training did not change a 60 second jumping power even though there is significantly increase in sprinting performance. Other studies showed isokinetic training of 1 limb produced significantly increments in isokinetic but not 1RM. The reason may have been a more statical power than the absence of training effect.

A marked reduction in the coefficient would suggest that the various form of dynamometry were not measuring similar adaptation, and this is the seminal issue when monitoring the effects of training.

Strength as an indicator for return to sport

Investigate the relationship between isokinetic strength of quadriceps and a single leg hop for distance test in healthy subjects. No significant difference existed between knee extensor strength and single leg hop distance performance was resulted. Statical analysis revealed that isokinetic strength does not correlate strongly with functional task. They suggested that isokinetic strength test alone is not a sufficient criterion for returning patients to functional activity.

Selected measures of physical and functional capability in anterior cruciate deficient athletes and their correlation with athletic ability were investigated. Result showed that peak torque ratio of quadriceps and hamstrings were not related to the functional capacity of subjects and may not have a great effect on the decision for return to sporting field.

Correlation of fitness test and athletic performance

Valid and standardised test should be built into training process for all performance relevant features of the sport in question. However, it is often difficult to measure fitness, which involves different energy systems and high level of technical skill in different sports.

Traditional standardised tests of cycle or treadmill ergometer were shown to be a poor indicator of performance in sports with the use of a sport specific field, only a moderate correlation (r = 0.65) was found. They suggested that other factor such a skill, agility and visual acuity were more indicative of performance although the test provides a reasonable assessment of fitness. For many sports involving non-rhythmic movements sport specific testing may be impossible or only performed using elaborate and expensive equipments.

Body girth tends to reduce or remain unchanged after a period of training and competition, and this cannot be explained by the training specificity. National standard female gymnasts showed a significant intra-season increase in body density when assess at the pre-, mid- and post season points and similar result found in elite swimmer in the preparation phase. Research has indicated that appropriate sport specific levels of relative fat and fat-free weight are beneficial to performance in sports. Body fat changes in response to season but no correlation with performance has been found. Inconsistency in the body density was most found in male athletes that cannot be useful for fitness evaluation.

Investigated the relationship between isokinetic strength of quadriceps and a single leg hop for distance test in healthy subjects. No significant difference existed between knee extensor strength and single leg hop distance performance was resulted. They concluded that a single leg functional performance test alone may be insufficient in the dynamic assessment of patient's functional level. The belief that functional test performance tests when compare to isokinetic measurements, mimic a more functional environment is well supported. However, the lack of tested validity of one single leg tests or many other functional test are unknown

Relationship of fitness and injury

Flexibility is part of the fitness assessment adopted because of the perceived relation between performance on these test and low back pain. However, this relationship was not well validated . A study on healthy examines the relationship between performance on muscular strength and flexibility (sit-up and sit-and-reach tests). Result showed that no relationship between sit-up and sit-and-reach test performance and reported low back pain. The sit-up and sit-and-reach tests provide no criterion-related validity . Therefore, these test are not suitable for health-related fitness batteries.

Do test measures discriminate between individuals?

Many sports scientists and coaches endeavour to develop test batteries, which discriminate between superior and lesser performers in heterogeneous and homogeneous samples. However, most of them have been in gross level between males, and females, young and old.

Negative Argument

Reliability and validity of strength measure

Isometric assessment techniques present high test-retest reliability with the reliability coefficients of range from 0.85 to 0.99 have been reported by a number of researchers. For isoinertial testing, it is dynamic and has a greater external validity than isometric assessment through the manipulation of the temporal sequencing of eccentric and concentric contractions; it is possible to activate the stretch-shorten cycle.

Resistant training of some non-specific strength can be transferred to the multitude of movement patterns of athletic performance. The advantage of isokinetic assessment over isoinertial protocols is that it is easier to achieve measurement reliability and objectivity. Besides, isokinetic devices are commercially available, including the Cybex, Kin-Com, Biodex and Merac systems. The test-retest reliability of isokinetic tests is generally high. While the reliability coefficients for eccentric contraction are slightly less than that for concentric contractions, they remain high.

Torque generation at high isokinetic speeds has been shown to be correlated with the fibre characteristics of the muscle. This may provide some important insight to factors implicated in the development of strength and power.

Strength and flexibility imbalance associated with athletic injuries

138 female collegiate athletes participated in various sports were administered preseason strength and flexibility tests and followed for injuries during their sports seasons. Result found that there was an association of higher injury rates with knee flexor or hip extensor imbalance of 15% or more on either side of the body. They concluded that specific strength and flexibility imbalance are associated with lower extremity injuries in female collegiate athletes. Strength imbalance in 180 deg/sec was related to injury, but no significant difference found in 30 deg/sec.

Fitness testing and performance

Twenty uninjured female subjects performed isotonic strength tests for the knee extensors in OKC and for hip, knee and ankle extensors in the squat exercise (CKC). Result showed that a consistent finding of a positive relationship between vertical jump and CKC strength is because of the similar functional requirement of the lower limb during the lifting stage of CKC muscle strength testing and the propulsive phase of jumping.

Maximum oxygen uptake was measured during a continuous treadmill running test. A sports specific test data was performed in a squash court. The maximum heart rate and lactate values showed that players were under maximum loading during the test field. A high correlation was found between the field test data and the ranked playing ability. The test provides a good baseline reference for coach, and athletes for future improvement of the squash team.

The motor abilities could be considered as being highly relevant for performance in tennis had to be singled out and ranked. 14 motor ability tests were used to assess the elite tennis player. There were significant correlations between the test result and the level of performance. Factor analysis further reveals single characteristics, which are the special agility in running, power and strength and endurance.

Seasonal Variation

When interpreting the result of fitness and strength evaluation, seasonal variation needs to be considered. A number of studies have described the effects of seasons or periods of competition, training, detraining and reduced training on aspects of fitness. Depending on the performance level, the type of sport and the fitness parameter, the swings in fitness variable reported may be as high as 18% from one season to another.

Maximal oxygen intake (VO2Max) and respiratory anaerobic threshold were measured in international male skiers. A seasonal deterioration in aerobic endurance and muscle strength does occur in these athletes. The literature indicated that apart from few isolated cases, components of anaerobic fitness show little seasonal variation in men and women of different competitive ability.

Repetitive assessments of peak anaerobic power by five 6-second all out cycling ergometer sprints, throughout a year of elite netball training and competition showed a significant improvement only the initial stages of the preparation season. This unexpected result showed that most of the tests currently used to evaluate anaerobic fitness do not appears to be sensitive enough to detect seasonal variations.

A 30 second Wingate type test, performed by male and female elite speed skaters 4 times a year, failed to detect any significant seasonal variation in mean and peak power, which led to seasonal progression in performance.

Competitor with relatively low aerobic capacities usually demonstrates noticeable fluctuations in aerobic fitness between seasons of training and detraining. For elite athletes, a VO2 max was significantly lower at the end than the beginning of the season assessment also reveal lower mean VO2 max and maximal respiratory exchange ratios in male elite fencers, compare with off season. Given that aerobic fitness may well contribute to sports success in activity lasting for more than 2 minutes, such changes in maximal respiratory parameters may result in impaired performances.

Conclusion

In conclusion, more research is needed to investigate the external validity and the standardised the procedure strength and fitness evaluation, so as to improve the usefulness of information gathered. The lack of consistency in the correlation of strength and fitness measures with athletic performance, training effects; injury potential and readiness to return to sport obviously hinder the benefit of testing. It is unlikely that one assessment procedure can be used for a multitude of ends, and different levels of athlete ability within a given sport may require different assessment regime and minor changes in procedure may alter the usefulness of a procedure.

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Exercise Physiology Educational Resources 2000