Piqueras-Sanchiz, Francisco; Cornejo-Daza, Pedro J.; Sánchez-Valdepeñas, Juan; Bachero-Mena, Beatriz; Sánchez-Moreno, Miguel; Martín-Rodríguez, Saúl; García-García, Óscar; Pareja-Blanco, Fernando

Journal of Strength and Conditioning Research: November 2022 - Volume 36 - Issue 11 - p 2983-2991, doi: 10.1519/JSC.0000000000004068

PURPOSE:

To investigate the effect of set configuration on mechanical performance, neuromuscular activity, metabolic response, and muscle contractile properties.

PROCEDURES:

Sixteen strength-trained men performed two barbell squat training sessions @ 1) 3 sets of 8 repetitions (3 x 8)/5:00 rest between sets and 2) 6 x 4/2:00 rest between sets:

· The amount of resistance used for each protocol was 75% of the one repetition maximum (1-RM).

· The total volume was 24 repetitions.

· The total rest time was 10:00.

· The training density were equalized between protocols.

The pre-tests performed before and after each protocol were:

· Tensiomyography (TMG).

· Blood lactate and ammonia concentration.

· Countermovement jump.

· Maximal voluntary isometric contraction in the squat.

· Muscle force, velocity, power output values, and electromyography data were recorded for every rep of each protocol.

CONCLUSIONS:

The 6 × 4 protocol resulted in greater force, velocity, power, and lower neuromuscular markers of fatigue compared to the 3 × 8, especially in the last reps of each set.

The 3 × 8 protocol created greater lactate and ammonia concentrations, greater reductions in jump height, and greater impairments in TMG-derived velocity of deformation compared to the 6 × 4.

Implementing lower rep sets with shorter and more frequent between-set rest time decreases impairments in mechanical performance, especially in the final reps of each set. These effects may be facilitated by lower neuromuscular alterations, reduced metabolic stress, and better muscle contractile properties.

IN PLAIN ENGLISH:

Regarding energy system involvement in strength training (or any other activity for that matter) in general, a high-effort, high intensity event that continues longer (i.e., the eight reps in the 3 x 8 protocol vs. the four reps of the 6 x 4 protocol) would result in greater lactic acid (LA) accumulation due to the involvement of the glycolytic system that kicks in to fuel the event. However, the amount of resistance used (in this case 75% of a 1-RM) and the length of recovery time between sets need to be factored in.

In example, assuming one rep takes :02.5 to complete, 8 x 2.5 = :20 while 4 x :02.5 = :10. Energy system involvement would be ATP-PC (:10) + glycolysis (remaining :10) for the :20 eight-rep event (more potential LA accumulation) while only :10 for the four-rep event that solely relies on the ATP-PC system to complete (less potential LA accumulation). Now consider the 75% of a 1-RM used for each event and the 2:00 (6 x 4) vs. 5:00 (3 x 8) recovery time between sets. Because only four reps were completed in the 6 x 4 event (far from complete muscle fatigue and minimal LA accumulation) the 2:00 recovery time was adequate enough to allow the ATP-PC system to recover to approximately 90%, thus returning it to near full capacity. Conversely, the 75% of a 1-RM for double the number of reps in the 3 x 8 event clearly led to greater LA accumulation (despite the 5:00 recovery), rendering the muscles less functional (and thus the inferior test results).