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

Rapid force development is a key factor influencing performance and injury risk in movements where little time is available for force production; thus there is a need to develop interventions that enhance this ability. In the present study, the influence of load knowledge on mechanical output [rate of force development; (RFD) and power] and muscle activation [electromyographic (EMG) responses] in the concentric-only bench press throw exercise was studied. Fifteen strength-trained individuals performed 6 sets of 6 maximal explosive repetitions in a single test session after extensive familiarization. In three of these sets the subjects were given knowledge about the load before each repetition (known condition; KC), whereas in the other three sets they were given no information (unknown condition; UC). In both conditions the loads were 30, 50 and 70 % of maximum, but condition and load orders were randomized. RFD (24–50 %) and power output (20–39 %) were significantly higher in UC in the early time intervals from movement onset (<150 ms). In addition, UC elicited greater EMG amplitudes in anterior deltoid both prior to movement onset (pre50–0 ms) and in the early time intervals (<100 ms) after movement onset, and in pectoralis major after movement onset (<100 ms). UC resulted in a greater initial activation of the muscles and both a higher RFD and mechanical power output in the early phase of the movement under all loading conditions (30–70 % of maximum). UC appears to offer a novel neuromuscular stimulus, and further research on the effects of continued exposure is warranted.

Load knowledge reduces rapid force production and muscle activation during maximal-effort concentric lifts

Flywheel Training Periodization in Team Sports.

This study aimed to evaluate the differences in power production between movement phases (i.e., concentric and eccentric) during the execution of resistance exercises with a flywheel device, differentiating between execution regimes (i.e., bilateral, unilateral dominant leg and unilateral non-dominant leg). Twenty young elite soccer players (U−17) performed two sets of six repetitions of the bilateral half-squat (inertia 0.025 kg·m−2) and the lateral-squat exercise (inertia 0.010 kg·m−2) on a flywheel device. During the testing sessions, mean and peak power in concentric (MPcon) and eccentric (MPecc) phases were recorded. The non-dominant leg showed higher values in all power variables measured, although substantial differences were only found in MPecc (ES = 0.40, likely) and PPcon (ES = 0.36, possibly). On the other hand, for both exercises, MPcon was higher than MPecc (ES = −0.57 to −0.31, possibly/likely greater), while only PPecc was higher than PPcon in the dominant lateral-squat (ES = 0.44, likely). These findings suggest that young soccer players have difficulty in reaching eccentric-overload during flywheel exercises, achieving it only with the dominant leg. Therefore, coaches should propose precise preventive programs based on flywheel devices, attending to the specific characteristics of each limb, as well as managing other variables to elicit eccentric-overload.

Eccentric-Overload Production During the Flywheel Squat Exercise in Young Soccer Players: Implications for Injury Prevention.

Obesity has become one of the major health problems of today’s society, being considered as an epidemic. For people with morbid obesity (Body Mass Index (BMI) ≥ 40 kg·m -2 ) who don’t lose weight using conventional weight reduction methods we must resort to bariatric surgery. There is controversy in the relationship between physical activity and weight loss after bariatric intervention. Therefore, the aim of this paper is to review and describe the different research existing about this topic. A literature review of Medline and Scopus databases was performed. From a total of 128 articles and after the exclusion criteria 24 full papers were read, out of which, 21 were observational research and 3 were experimental research. We found that physical activity positively correlated with weight loss; however, although there are no significant differences in the short term (six months), differences begin to be seen in the medium to long term (+ 9 months).

http://www.eurjhm.com/index.php/eurjhm/article/download/323/542

Bariatric surgery, weight loss and the role of physical activity: a systematic review

The purpose of the present meta-analysis was to examine the effect of flywheel resistance training (FRT) on main sport action (i.e., jumping performance, sprinting time and change of direction performance) improvements in athletes and healthy active people. A Boolean search strategy adapted for each of the databases employed was conducted to identify all studies measuring change in sport actions performance after FRT interventions up to July 2019. Outcomes were analysed using an average effect size (D+) and a 95% confidence interval (CI), which was calculated assuming a random-effects model. A total of 9 studies with 283 participants met the inclusion criteria and were selected for the analysis. The mean quality score (PEDro scale) of the articles included in the meta-analysis was 5.67. The meta-analysis showed significant positive effects on jumping performance (SMC 0.65; 95% CI, 0.11-1.19; p = 0.02), sprinting time (SMC 1.33; 95% CI, 0.39-2.28; p < 0.01) and change of direction performance (SMC 1.36; 95% CI, 0.58-2.14; p < 0.01) after FRT interventions compared to control/traditional resistance training groups. The results of the present meta-analysis provide evidence of the usefulness of FRT to improve variables related to sport performance in both athletes and healthy population.

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Jose Luis Hernández-Davó

Papers

Load knowledge reduces rapid force production and muscle activation during maximal-effort concentric lifts

Flywheel Training Periodization in Team Sports.

Eccentric-Overload Production During the Flywheel Squat Exercise in Young Soccer Players: Implications for Injury Prevention.

Bariatric surgery, weight loss and the role of physical activity: a systematic review

Effects of Flywheel Resistance Training on Sport Actions. A Systematic Review and Meta-Analysis.