Effect of Instability on Power and Speed in Bench Press

The aim of this study was to analyse and compare the speed and power parameters in bench press training in different degrees of instability: 1) stable (PBE), 2) with asymmetric load (PBA), 3) with oscillating load (PBO), 4) on fitball (PBF) and 5) on bosu (PBB). For this purpose, 20 male subjects (10 trained and 10 untrained) with specific experience in training under unstable conditions were evaluated with respect to mean propulsive velocity (MPV), maximum velocity (MV) and power (POT) with different types of external load: low load (40% of 1RM), medium load (60% of 1RM) and high load (80% of 1RM) in each condition.

Therefore, the aim of this study was to analyse the effect of different degrees of instability on power and speed of execution in the bench press exercise. For the design of this quasi-experimental research, with an ad hoc protocol, an intersubject comparison was used in 5 different conditions. 20 male participants were grouped into two groups based on their previous experience with unstable training and volunteered for this study. Expert group (n= 10; 23.70 ± 4.30 years; 81.40 ± 9.67 kg; 179.50 ± 8.95 cm; 3.5 ± 4.10 years of strength training experience; 9 ± 10.60 months of unstable training experience) Novice group (n= 10; 25.60 ± 6.50 years; 77.80 ± 4.44 kg; 176.40 ± 2.80 cm; 3.40 ± 1.96 years of strength training experience; 0.90 ± 0.99 months of unstable training experience). Subjects with no experience in training with unstable loads (having implemented unstable loads in their training at some point) or current or recent injuries (within the last 6 months) that caused them to alter their normal physical activity were excluded from this study. This study was in accordance with the Declaration of Helsinki (2013). All participants gave written informed consent prior to the study. Subjects performed the bench press exercise by assessing mean propulsive velocity and power with 3 different loads for each of the unstable situations: light (40% of 1RM), moderate (60% of 1RM) and high (80% of 1RM). In a familiarisation session, subjects performed the relative loads with each condition to determine their strength-velocity profiles and their optimal work percentages. In addition, an incremental load test was performed to determine the 1RM of each of the participants to determine the external load for each load percentage in each of the subjects.

Each subject performed 3 repetitions for the light load (40% RM; VMP > 1.0 m/s), with 1 minute rest; 2 repetitions for the medium load (60% RM; 0.65 m/s ≤ VMP ≤ 1.0 m/s) with 2 minutes rest and 1 repetition for the heavy load (80% RM; VMP < 0.65 m/s) with 4 minutes rest. A metronome was used for the start countdown and to time the eccentric and concentric portions of the exercise. Subjects began the bench press with their elbows fully extended, maintaining a grip distance slightly greater than shoulder width. The bar was then lowered to their chest and then applying as much thrust as possible until full elbow extension on a 2-1-0 count. The timing sequence involved 2 seconds for the eccentric phase, a 1 second hold (to minimise the contribution of the rebound effect and allow for more reproducible and consistent measurements) and for the concentric "up" phase the highest possible execution speed, until the bar returned to the starting position.

Inclusion Criteria: two years of continuous strength training experience a minimum of 6 months of suspended training experience Exclusion Criteria: Athletes who presented pain or skeletal or neuromuscular disorder