California State University, Fullerton, CA Upper Body Muscle

Upper Body Muscle Activation Between Stable and Unstable Load During Eccentric Bench Press Dustin D. Dunnick  Saldiam R. Barillas  Lee E. Brown, FACSM  Jared W. Coburn, FACSM  Scott K. Lynn Human Performance Laboratory  Department of Kinesiology  California State University, Fullerton, CA INTRODUCTION

RESULTS

INTRODUCTION: The bench press is one of the most commonly used upper body exercises in training. There is conflicting research on use of an unstable surface, but little to no research on the use of an unstable load (UL). PURPOSE: To investigate muscle activation during the eccentric phase of a bench press while using a stable load (SL) and UL. METHODS: Twelve males (age= 24.3 ± 2 yrs.; height= 177.0 ± 6.8 cm; mass= 87.6 ± 11.4 kg) completed 2 experimental conditions (SL and UL) at two different intensities [60% 1RM and 80% 1RM]. UL was achieved by hanging 16kg kettlebells by elastic bands from the end of the bar. All trial lifts were set to a two second cadence with a hold at the bottom of the lift. Subjects had electrodes attached to 5 muscles [pectoralis major (PM), anterior deltoid (AD), medial deltoid (MD), triceps brachii (TB) and latissimus dorsi (LD)] and performed three isometric bench press trials to normalize electromyography data. After 48 hours, subjects completed the opposite condition. RESULTS: There was no effect of intensity but there was an interaction of condition and muscle. The AD had significantly greater muscle activation using UL (0.69 ± 0.21 relative to MVIC) compared to SL (0.63 ± 0.22 relative to MVIC). All other muscles showed no significant differences. CONCLUSIONS: These results suggest that the use of an UL may increase AD activation during the eccentric phase. The use of an UL could be incorporated into training to increase muscle activation.

The bench press is one of the most commonly used upper body exercises in training. There is conflicting research on use of an unstable surface, but little to no research on the use of an unstable load (UL).

There was no effect of intensity but there was an interaction of condition and muscle. The AD had significantly greater muscle activation using UL compared to SL (Figure 3). All other muscles showed no significant differences.

PURPOSE To investigate muscle activation during the eccentric phase of a bench press while using a stable load (SL) and UL.

Figure 1. Unstable load.

METHODS Twelve males (age= 24.3 ± 2 yrs.; height= 177.0 ± 6.8 cm; mass= 87.6 ± 11.4 kg) completed 2 experimental conditions (SL and UL) (Figures 1 & 2) at two different intensities [60% 1RM and 80% 1RM]. UL was achieved by hanging 16kg kettlebells by elastic bands from the end of the bar. All trial lifts were set to a two second cadence with a hold at the bottom of the lift. Subjects had electrodes attached to 5 muscles [pectoralis major (PM), anterior deltoid (AD), medial deltoid (MD), triceps brachii (TB) and latissimus dorsi (LD)] and performed three isometric bench press trials to normalize electromyography data. After 48 hours, subjects completed the opposite condition.

Relative to MVIC

ABSTRACT

1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0

*

Pectoralis Major

Anterior Deltoid Stable Load

Medial Deltoid

Triceps Brachii

Latissimus Dorsi

Unstable Load

Figure 3. Muscle activation during eccentric bench press. * Unstable significantly greater than stable.

CONCLUSIONS Figure 2. Stable load.

These results suggest that the use of an UL may increase AD activation during the eccentric phase. The use of an UL could be incorporated into training to increase muscle activation.