Training methods and planning

Classification of Jerk-from-the-Chest Exercises and How to Use Them at Different Skill Levels

A. S. Medvedev, N. A. Masalgin, A. G. Errera, V. I. Frolov, State Central Institute of Physical Culture (GTsOLIFK)

English summary of Tyazhelaya Atletika. Ezhegodnik 1982 (Moscow: Fizkultura i Sport, 1982), pp. 15–17: the text is paraphrased, not translated; data tables are given in full with English labels.

Background

• At the XXII Olympics (104 Olympic records, 18 of them world records), half of all attempts were missed, and two-thirds of the misses came in the jerk from the chest.
• Known facts: the best bar path is vertical, and the optimal dip is about 10% of the lifter's height (A. Ivanov, 1975). The jerk has 3 periods and 6 phases. The key phase is braking: the shorter it is, the higher the force on the platform (r = 0.79).
• Assistance exercises had never been ranked by effectiveness. The only guideline was S. Arutyunyan's (1965): 89% weights, at most 5 lifts per session.

Tasks and methods

• Tasks: rank assistance exercises, find the optimal number of 90% lifts per session, and find exercises that best mobilise speed-strength.
• Recording: ground reaction force, bar path, knee angles and the EMG of the lateral quadriceps, recorded together.
• Subjects: 150 lifters at GTsOLIFK and at the Manuel Fajardo Institute in Havana: students, youth lifters and the Cuban national team. Over 1000 lifts and 7000 parameters were analysed.
• Exercises (90% of the best classic jerk): classic jerk; jerk from racks; jerk from behind the head; wide-grip jerk; push jerk; half-jerk.

Four parameters proved informative at every skill level: peak platform force F_max, time to reach it t₁, braking time t₂, and the EMG-based motor-unit mobilisation time F.A. ("frontal analysis"), which correlates with F_max.

Table. Technique parameters and EMG characteristics in jerk exercises (means)

* Printed 0.97, implausible beside 0.121–0.173; probably 0.097.

Findings

• Ranking: 1) behind the head; 2) from racks; 3) classic jerk; 4) push jerk; 5) wide-grip jerk; 6) half-jerk. Only the last two differed significantly from the rest.
• Why behind the head is best: the centres of gravity line up, so force passes rigidly to the bar. With the bar on the chest, the centre of gravity shifts forward and the abdominal muscles absorb part of the drive.
• Push jerk: F_max and t₁ are close to the classic jerk, but motor units are mobilised slowly.
• Half-jerk with rubber resistance (a 1-cm cord fixed to the floor and the bar, 5 kg tension at the chest): F_max rose from 204% to 284%, and t₁ fell from 0.4 to 0.33 s.
• Depth jumps (40 and 70 cm): mobilisation took 0.094–0.1 s against 0.129–0.131 s in the jerk, and F_max was 300% or more.
• Fatigue across sets (one lift per set): intramuscular coordination (F.A., EMG) deteriorates first and the external parameters later. Significant decline begins at sets 4–5 in qualified lifters and at sets 6–7 in less qualified ones. In the rubber half-jerk, F_max drops from set 8.

Recommendations

• Refine the jerk with the jerk from behind the head and the jerk from racks.
• Develop explosive strength with the rubber half-jerk and depth jumps, especially in advanced lifters.
• Jerk from racks at 90%, single lifts: at most 7 sets for 3rd-class lifters, at most 5 for 1st-class lifters and Masters of Sport.
• Rubber half-jerk at 90%: at most 8 sets, at any skill level.
• Do not overuse the push jerk. The half-jerk and the wide-grip jerk are strength-building aids.