Where does recruitment collide?

The progressive activation of additional motor units to raise the force a muscle produces: as the demand grows, the nervous system brings more motor units into play, and it does so in a broadly orderly sequence from smaller units to larger ones. Henneman's 1957 Relation between size of neurons and their susceptibility to discharge reported the size relationship that underlies this order, later known as the size principle. The referent is the switching-on of motor units within a working muscle, graded by force, and it is not the sourcing of job applicants, the entry of young fish into a stock, or the summoning of immune cells to a wound.[1]

Unit

The number and firing of motor units active in a muscle, at a given force

Recovery means

When force demand falls the units are derecruited, in a broadly reverse order, and stop firing

Measured by

Recorded by surface and intramuscular electromyography, and by decomposing the signal into single motor unit firings

The activities an organisation undertakes to identify, attract, and secure a pool of candidates for its open positions, and to keep promising applicants interested through the hiring process. Breaugh's 2008 Employee recruitment: Current knowledge and important areas for future research reviewed how recruitment sources, messages, and timing shape who applies and who stays in the pool. The referent is an employer's effort to source and draw in people for jobs, counted by applicants and yield, and it shares nothing with a muscle switching on motor units, a fishery gaining young fish, or leukocytes moving to a site of infection beyond the word.[2]

Unit

The flow of job applicants an organisation attracts to its openings

Recovery means

Not applicable

Measured by

Tracked by applicant counts, source yield, quality of hire, and the proportion of candidates who remain in the process

The number of new individuals that survive to enter a population or a fishery over a period, typically the young that reach a defined age or size where they first become part of the exploitable stock. Ricker's 1954 Stock and recruitment set out how the size of the spawning stock relates to the recruitment it produces, giving the reproduction curve that carries his name. The referent is a count or rate of fresh entrants to a population, read year by year, and it is a different thing from a muscle recruiting motor units, an employer recruiting staff, or a tissue recruiting immune cells.[3]

Unit

The number of new individuals entering a stock in a year or season

Recovery means

Not applicable

Measured by

Estimated from surveys of young year-classes, catch-at-age data, and stock assessment models fitted to a stock-recruitment relationship

The summoning of circulating immune cells out of the blood and into a site of infection or injury: white cells are captured on the vessel wall, roll, arrest, and then cross into the tissue, guided by adhesion molecules and chemical signals. Ley, Laudanna, Cybulsky, and Nourshargh's 2007 Getting to the site of inflammation: the leukocyte adhesion cascade updated set out the steps of this cascade. The referent is the directed movement of leukocytes to an inflamed site, described cell by cell, and it is unrelated to a muscle activating motor units, an employer drawing in applicants, or fish entering a stock.[4]

Unit

The passage of leukocytes from blood into an inflamed tissue

Recovery means

The recruited cells clear or die as inflammation resolves, and the vessel wall returns to a resting, non-adhesive state

Measured by

Observed by intravital microscopy of rolling and adhesion, and quantified by counting leukocytes that infiltrate the tissue