Effect of Instability on Power and Speed in Bench Press
Condition: Instability, Joint
MeSH terms: Joint Instability
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): Power and execution speed as a function of instability experience
Intervention type(s): Other
Intervention description(s): 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.
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Other
Keywords: Strength Training; Unstable Devices; Balance; Speed Training; Core