Statistical Methods for Health Care Research

For the statistical consultant working with social science researchers the estimation of reliability and validity is a task frequently encountered. Measurement issues differ in the social sciences in that they are related to the quantification of abstract, intangible and unobservable constructs. In many instances, then, the meaning of quantities is only inferred. Let us begin by a general description of the paradigm that we are dealing with. Most concepts in the behavioral sciences have meaning within the context of the theory that they are a part of. Each concept, thus, has an operational definition which is governed by the overarching theory. If a concept is involved in the testing of hypothesis to support the theory it has to be measured. So the first decision that the research is faced with is \" how shall the concept be measured? \" That is the type of measure. At a very broad level the type of measure can be observational, self-report, interview, etc. These types ultimately take shape of a more specific form like observation of ongoing activity, observing video-taped events, self-report measures like questionnaires that can be open-ended or close-ended, Likert-type scales, interviews that are structured, semi-structured or unstructured and open-ended or close-ended. Needless to say, each type of measure has specific types of issues that need to be addressed to make the measurement meaningful, accurate, and efficient. Another important feature is the population for which the measure is intended. This decision is not entirely dependent on the theoretical paradigm but more to the immediate research question at hand. 6/14/2016 2 A third point that needs mentioning is the purpose of the scale or measure. What is it that the researcher wants to do with the measure? Is it developed for a specific study or is it developed with the anticipation of extensive use with similar populations? Once some of these decisions are made and a measure is developed, which is a careful and tedious process, the relevant questions to raise are \" how do we know that we are indeed measuring what we want to measure? \" since the construct that we are measuring is abstract, and \" can we be sure that if we repeated the measurement we will get the same result? \". The first question is related to validity and second to reliability. Validity and reliability are two important characteristics of behavioral measure and are referred to as …

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Validity and reliability.

Rate of force development (RFD) refers to the ability of the neuromuscular system to increase contractile force from a low or resting level when muscle activation is performed as quickly as possible, and it is considered an important muscle strength parameter, especially for athletes in sports requiring high-speed actions. The assessment of RFD has been used for strength diagnosis, to monitor the effects of training interventions in both healthy populations and patients, discriminate high-level athletes from those of lower levels, evaluate the impairment in mechanical muscle function after acute bouts of eccentric muscle actions and estimate the degree of fatigue and recovery after acute exhausting exercise. Notably, the evaluation of RFD in human skeletal muscle is a complex task as influenced by numerous distinct methodological factors including mode of contraction, type of instruction, method used to quantify RFD, devices used for force/torque recording and ambient temperature. Another important aspect is our limited understanding of the mechanisms underpinning rapid muscle force production. Therefore, this review is primarily focused on (i) describing the main mechanical characteristics of RFD; (ii) analysing various physiological factors that influence RFD; and (iii) presenting and discussing central biomechanical and methodological factors affecting the measurement of RFD. The intention of this review is to provide more methodological and analytical coherency on the RFD concept, which may aid to clarify the thinking of coaches and sports scientists in this area.

Physiological and methodological aspects of rate of force development assessment in human skeletal muscle.

The purpose of this review was to provide a physiological rationale for the use of eccentric resistance training and to provide an overview of the most commonly prescribed eccentric training methods. Based on the existing literature, there is a strong physiological rationale for the incorporation of eccentric training into a training program for an individual seeking to maximize muscle size, strength, and power. Specific adaptations may include an increase in muscle cross-sectional area, force output, and fiber shortening velocities, all of which have the potential to benefit power production characteristics. Tempo eccentric training, flywheel inertial training, accentuated eccentric loading, and plyometric training are commonly implemented in applied contexts. These methods tend to involve different force absorption characteristics and thus, overload the muscle or musculotendinous unit in different ways during lengthening actions. For this reason, they may produce different magnitudes of improvement in hypertrophy, strength, and power. The constraints to which they are implemented can have a marked effect on the characteristics of force absorption and therefore, could affect the nature of the adaptive response. However, the versatility of the constraints when prescribing these methods mean that they can be effectively implemented to induce these adaptations within a variety of populations.

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Implementing Eccentric Resistance Training-Part 1: A Brief Review of Existing Methods.

Purpose: To analyze the effects of different inertial loads on power production and power maintenance, as well as the number of sessions required for proper familiarization during the flywheel quarter-squat. Methods: Twenty-four high-level handball players attended 4 testing sessions consisting of 4 sets of 10 repetitions using 4 different inertial loads (0.025, 0.050, 0.075, and 0.100 kg·m2). In addition, a 5th set of 15 repetitions was performed. Both concentric and eccentric peak power and the eccentric:concentric ratio were recorded. Results: The results showed the need to perform 3 sessions for a proper familiarization (ie, outcomes stabilization). The inertial load of 0.025 kg·m2 led to greater concentric peak power compared with the other inertial loads (from likely to most likely greater values). Both 0.025 and 0.050 kg·m2 inertial loads entailed greater eccentric peak power compared with 0.075 and 0.100 kg·m2 (most likely greater). Conversely, the 0.025-kg·m2 inertial load showed a lower eccentri...

Influence of Different Inertial Loads on Basic Training Variables During the Flywheel Squat Exercise

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Load Quantification and Testing Using Flywheel Devices in Sports.

Explosive muscular contractions are fundamental to sports activities such as sprinting, jumping or throwing. In these types of contractions the rate at which force is developed has been suggested to be the most important physical capacity. Therefore, the aims of these review was: to review the reliability of rate of force development (RFD) measures; to show the relationships between  RFD and performance in specific sports movements; and to provide information about the response of RFD variables to different training interventions. From a total of 655 articles, after the exclusion criteria 60 articles were read. RFD has shown high to very high reliability in most of the studies, independently of the device used or the specific variable measured. The RFD at early time intervals has shown the higher correlations with performance in several sports movements. In addition, RFD at early time intervals has been shown sensitive to most training interventions, therefore, it seems to be the key point among RFD variables.

https://dialnet.unirioja.es/descarga/articulo/5113120.pdf

Rate of force development: reliability, improvements and influence on performance. A review.

Muscle hypertrophy has been associated with both athletic performance and quality of life. Although hypertrophy-oriented resistance training methodologies are very popular, it is still unclear the different physiological and perceptual responses to some of these methodologies. The aim of this study was to compare the acute effects of four different hypertrophy-oriented resistance training methodologies. During four weeks, seventeen participants with experience in resistance training performed a once-a-week resistance training session, differing the methodology (traditional, pyramid, agonist supersets and agonist paired supersets). Acute responses to the different training sessions were measured via lactate concentration, peak velocity losses, rating of perceived exertion, and number of assisted repetitions. Both lactate concentration and rating of perceived exertion showed that the agonist paired supersets caused greater values compared with either the traditional or the pyramid methodologies. Although all of the methodologies led to significant decreases in peak velocity, these decreases were not different between methodologies. The results of the present study highlight the agonist paired supersets as being the most stressed methodology when talking about acute fatigue responses to a single training session. Further research is required to evaluate if these large acute fatigue effects could lead to greater muscle hypertrophy following a training intervention.

https://dialnet.unirioja.es/descarga/articulo/5774948.pdf

Comparison of acute responses to four different hypertrophy-oriented resistance training methodologies

Abstract The aim of this research was to assess the reliability of a specific change of direction test (i.e., “On-Court COD test”) in youth badminton players, evaluate the effect of age on On-Court COD performance, and examine its correlations with linear speed, change of direction speed, and vertical jump tests. Forty-two young badminton players (27 males and 15 females; age: 17.3±1.6 years, body height: 170.3±7.5 cm, body mass: 59.0±9.7 kg) were divided into two age groups (Under 17 years and under 19 years). Tests included: linear sprints (5, 10, and 20-m), bilateral/unilateral countermovement jumps, a hexagon test, traditional and modified 505 change of direction tests; and On-court COD. Results showed an excellent intraclass correlation coefficient score (0.90) and a very low coefficient of variation values (1.6%) for the On-Court COD test. Comparing age groups, under 19 players were significantly faster in linear sprints (i.e., 5, 15 and 20-m; small to moderate effect sizes) and in all change of direction tests (moderate to large effect sizes). Moreover, the On-Court COD test showed moderate to large (r=.513-.779) relationships with both acceleration and COD abilities in under 17 players, and with linear sprints, COD, and jump performances in under 19 players. These data indicate that the On-Court COD test is a useful and reliable means to assess COD performance in youth badminton players and it is associated with acceleration, sprint and jump performance.

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On-Court Change of Direction Test: an Effective Approach To Assess COD Performance in Badminton Players

Background Eccentric overload training (EOT) has been proposed as an effective stimulus to optimize dynamic athletic performance. Nevertheless, the appropriate intensity during EOT remains unknown. The purpose of this study was to evaluate the influence of the inertial load used during an EOT program on performance adaptations in rugby union players. Methods Fifteen rugby players were divided into a low (0.025 kg·m2; G 0.025) or a high (0.075 kg·m2; G 0.075) inertial load for training. Both groups trained using the flywheel half squat exercise twice a week during the seven-week EOT. Athletic performance was evaluated by testing the half squat maximum repetition (1RM), countermovement jump (CMJ), 40 m linear sprint, the modified agility T-Test, and power output in the flywheel squat exercise. Data were analysed using magnitude-based inferences. Results Both groups improved their 1RM and CMJ to a similar extent. Nevertheless, the G 0.025 showed likely trivial changes in linear sprint (ES=-0.02), and possibly positive effects on the agility T-Test (ES=0.16), while the G 0.075 showed possibly negative effects on 40 m linear sprint (ES=-0.23) and likely trivial effects on the T-Test (ES=0.07). Conclusions Due to the similar gains in 1RM and CMJ, and the superior maintenance in linear sprint, the use of low inertial loads during EOT may be a better option when looking for athletic performance optimization.

Jose Luis Hernández-Davó

Papers

Load Quantification and Testing Using Flywheel Devices in Sports.

Rate of force development: reliability, improvements and influence on performance. A review.

Comparison of acute responses to four different hypertrophy-oriented resistance training methodologies

On-Court Change of Direction Test: an Effective Approach To Assess COD Performance in Badminton Players

Differential effects of low vs. high inertial loads during an eccentric-overload training intervention in rugby union players: a preliminary study.