Biceps Brachii Regional Growth In Response To 12-weeks Of Resistance Training: 681 5:00 PM - 5:15 PM

Resistance training causes skeletal muscle to increase in size. The biceps brachii flexes the forearm and supinates the hand, and therefore must not only resist any weight that is held in the hand but also must resist any turning effect caused by the hand held weight.

PURPOSE

To determine if elbow flexion resistance training causes a differential growth pattern in three distinct regions of the biceps brachii, near the origin (top of upper arm), the belly (middle of upper arm), and near the insertion (bottom of upper arm).

METHODS

68 subjects (49F, 19M) (25.9±0.8 y, 68.9±12.0 kg, 169.2±1.0 cm, mean ± SEM) participated in a 12wk non-dominant biceps strength training program. A progressive periodized training protocol consisting of 4wks of 12 reps (65–75% IRM), 5wks of 8 reps (75–82% 1RM) and 3wks of 6 reps (83–90% 1RM) was employed. The exercises included a preacher bench curl, concentration curl, and standing curl. Subjects were studied pre- and post-training using MRI. A series of axial slices (15 slices, 16mm slice thickness, 0mm interscan spacing, 256 ± 192 matrix, 22 ± 22cm FOV) were collected to study a 24cm length of the upper arm. Volumes were calculated by determining the number of pixels in an assigned region of interest (ROI) within each successive slice, calculating the area (cm2) of each ROI, multiplying by the slice thickness (1.6cm), and summing the successive slice volumes. Pre-training volumes subtracted from post-training volumes yielded training-induced change in volume.

RESULTS

Three-slice volumes, compared for the origin, belly, and insertion regions, revealed differential growth. Biceps brachii volumes increased by 5.5±0.7mL (origin), 8.8±1.1mL (belly) and 12.6±1.3mL (insertion) (p<0.05).

CONCLUSIONS

These results indicate training-induced differential growth within the three regions of biceps brachii tested, with the largest change in volume near the insertion. This may have resulted from an increased training challenge experienced near the insertion due to a greater torque requirement needed to maintain proper hand supination.

Supported by: NIH-IDS RO1 NS40606-02