Research methods

A Device for Measuring the Parameters of Bar Motion

A. Komor, Poland

English summary of Tyazhelaya Atletika. Ezhegodnik 1982 (Moscow: Fizkultura i Sport, 1982), pp. 69–70: the text is paraphrased, not translated; figures are the original images.

Abridged from Sport Wyczynowy (Poland), 1980, No. 10, pp. 51–56; prepared by G. Sverkunova. The editors describe it as giving immediate bar-motion data in training.

Design

Free-standing steel housing. On top: parameter selectors, auto-scaling switches for velocity and acceleration, a manual set-up key, the mains switch, and six coaxial outputs (X, Y, Vx, Vy, ax, ay).
Inside: pulse rotation sensors and conversion electronics.

Principle

A cord runs to the middle of the bar. The device measures its exit angle α and length R (polar coordinates).
These are converted to X, Y and differentiated: Vx = dx/dt, Vy = dy/dt, ax = d²x/dt², ay = d²y/dt².
Auto-scaling sets the recorder signal equal to 5 m/s or 10 m/s², so values are read straight from the chart.

Sketch of a bar pulling a cord from a braked drum with angle and length sensors feeding a converter — Fig. Device for recording bar motion: 1 — bar; 2 — cord; 3 — cord-extension sensor; 4 — cord exit-angle sensor; 5 — braking motor; 6 — converter; 7 — bar path.

Records

Bar-path diagrams: quantitative (deviation from the vertical, momentary dips of the bar) and qualitative (smoothness).
Phase diagrams: likewise; e.g. bar velocity at any height.
Velocities and accelerations against time.
Works for any point of the body or apparatus, except very large, fast or impact movements. Well received by athletes and coaches.

Acceleration unit printed “10 m/c” (m/s² meant); the printed ax, ay formulas show “dt” in the denominator.