Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

Stratified Sampling Method

Stratified Sampling Method

Sampling is a technique to select a portion (or subset) of the larger population and study that portion (the sample) to gain information about the population. The sampling method ensures that samples are drawn without bias and accurately represent the population. Because measuring the entire population in a study is not practical, researchers use samples to represent the population of interest.
To choose a stratified sample, divide the population into groups called strata and then take a...

Cross-Sectional Research

Cross-Sectional Research

In cross-sectional research, a researcher compares multiple segments of the population at the same time. If they were interested in people's dietary habits, the researcher might directly compare different groups of people by age. Instead of following a group of people for 20 years to see how their dietary habits changed from decade to decade, the researcher would study a group of 20-year-old individuals and compare them to a group of 30-year-old individuals and a group of 40-year-old...

Group Design

Group Design

The most basic experimental design involves two groups: the experimental group and the control group. The two groups are designed to be the same except for one difference— experimental manipulation. The experimental group gets the experimental manipulation—that is, the treatment or variable being tested—and the control group does not. Since experimental manipulation is the only difference between the experimental and control groups, we can be sure that any differences between the two are due to...

Body Water Content and Fluid Compartments

Body Water Content and Fluid Compartments

Life's biochemical processes occur within aqueous solutions. Solutes are substances that are dissolved within these solutions. The human body contains a variety of solutes, which can differ across various body parts. These can encompass proteins—such as those responsible for clotting and carbohydrate transport—as well as electrolytes. In medicine, an electrolyte is often described as a mineral ion derived from a salt possessing an electric charge. Examples include sodium ions (Na+) and chloride...

Buoyancy and Stability for Submerged and Floating Bodies

Buoyancy and Stability for Submerged and Floating Bodies

In fluid mechanics, buoyancy and stability are key concepts for understanding the behavior of submerged and floating bodies. When a stationary body is fully or partially submerged in a fluid, the fluid exerts a force on the body known as the buoyant force. This force acts vertically upward through a point called the center of buoyancy, which is the center of the displaced fluid volume. According to Archimedes' principle, the magnitude of the buoyant force is equal to the weight of the fluid...

Longitudinal Research

Longitudinal Research

Sometimes we want to see how people change over time, as in studies of human development and lifespan. When we test the same group of individuals repeatedly over an extended period of time, we are conducting longitudinal research. Longitudinal research is a research design in which data-gathering is administered repeatedly over an extended period of time. For example, we may survey a group of individuals about their dietary habits at age 20, retest them a decade later at age 30, and then again...

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Safe cold-water thresholds while wearing wetsuits approved for open water swimming competitions.

Journal of applied physiology (Bethesda, Md. : 1985)·2026

Same author

Artificial Intelligence Model for Automated Identification of Bowel Preparation for Colonoscopy (AI-PREPOO): A Multicenter Study.

Journal of gastroenterology and hepatology·2026

Same author

Efficacy of budesonide and vedolizumab for IBD-U associated with Muckle-Wells syndrome.

Clinical journal of gastroenterology·2025

Same author

Machine-Learning Prediction of Bleeding After Endoscopic Submucosal Dissection for Early Gastric Cancer: A Multicenter Study.

JGH open : an open access journal of gastroenterology and hepatology·2025

Same author

Recombinant human fibroblast growth factor and autogenous bone for periodontal regeneration: Alone or in combination? A randomized clinical trial.

Journal of periodontal research·2024

Same author

Duodenal Diverticular Bleeding Treated with Endoscopy or Transcatheter Arterial Embolization: A Report of Two Cases and a Literature Review.

Internal medicine (Tokyo, Japan)·2023

Search research articles

Related Experiment Video

Updated: May 26, 2026

A Rapidly Incremented Tethered-Swimming Maximal Protocol for Cardiorespiratory Assessment of Swimmers

A Rapidly Incremented Tethered-Swimming Maximal Protocol for Cardiorespiratory Assessment of Swimmers

Published on: January 28, 2020

Multi-age-grouping paradigm for young swimmers.

Kosuke Kojima¹, Paul L Jamison, Joel M Stager

¹Department of Kinesiology, Indiana University, Bloomington, Indiana 47405, USA. kokojima@indiana.edu

Journal of Sports Sciences

|December 21, 2011

Summary

USA Swimming

Area of Science:

Sports Science
Biomechanical Analysis
Youth Athletics

Background:

Current youth sports classification systems often use multi-age groupings.
These systems may not accurately reflect developmental differences in athletes.
USA Swimming utilizes unisex multi-age groupings for competitive swimming.

Purpose of the Study:

To evaluate the effectiveness of multi-age classification in youth swimming.
To analyze the rationale behind USA Swimming's multi-age groupings.
To propose alternative classification systems for competitive swimming.

Main Methods:

Analysis of top 100 US swim performances from 2005-2007.
Inclusion of data for girls and boys across 15 age groups (7-20 years).

More Related Videos

Automated Analysis of C. elegans Swim Behavior Using CeleST Software

Automated Analysis of C. elegans Swim Behavior Using CeleST Software

Published on: December 7, 2016

Swimming Performance Assessment in Fishes

Swimming Performance Assessment in Fishes

Published on: May 20, 2011

Related Experiment Videos

Last Updated: May 26, 2026

A Rapidly Incremented Tethered-Swimming Maximal Protocol for Cardiorespiratory Assessment of Swimmers

A Rapidly Incremented Tethered-Swimming Maximal Protocol for Cardiorespiratory Assessment of Swimmers

Published on: January 28, 2020

Automated Analysis of C. elegans Swim Behavior Using CeleST Software

Automated Analysis of C. elegans Swim Behavior Using CeleST Software

Published on: December 7, 2016

Swimming Performance Assessment in Fishes

Swimming Performance Assessment in Fishes

Published on: May 20, 2011

Calculation of mean swim times for seven competitive events, stratified by age and sex.

Main Results:

Significant age-related differences in swim performance were observed up to age 14 for girls and 16 for boys.
These performance disparities indicate that multi-age groupings may not ensure competitive fairness.
Boys exhibited later age-related performance maturation compared to girls.

Conclusions:

Stratifying swimmers by single age is the most equitable method for ensuring competitive fairness.
Current multi-age systems in youth swimming may disadvantage younger athletes.
A rationale for separate unisex competitive groups for swimmers under 8 years is lacking.