EMG analysis while using a smartphone

The purpose of this study was to clarify the influence of different postures on the activity of the shoulder girdle and lower back muscles while using a smartphone. Sixteen healthy male participants maintained two postures while using a smartphone : a good posture in which the tragus and acromion were closer to the vertical line passing through the greater trochanter, and a poor posture in which the tragus and acromion were farther from the vertical line passing through the greater trochanter. The target muscles were the rhomboid major (Rhom), upper trapezius, middle trapezius, lower trapezius (LT), lumbar erector spinae (LES), and lumbar multifidus (LMF). The activities of the Rhom and LT were significantly lower with poor posture than those with good posture. The activities of LES and LMF were significantly higher with poor posture than those with good posture. The results of this study indicated that poor posture was associated with hypoactivity of the shoulder girdle muscles and hyperactivity of the lower back muscles when compared with good posture. Poor posture for prolonged periods while using a smartphone would lead to malfunction of the shoulder girdle muscles and musculofascial lower back pain

On Weighted-Sum Orthogonal Latin Squares and Secret Sharing

Latin squares are a classical and well-studied topic of discrete mathematics, and recently Takeuti and Adachi (IACR ePrint, 2023) proposed (2,n)-threshold secret sharing based on mutually orthogonal Latin squares (MOLS). Hence efficient constructions of as large sets of MOLS as possible are also important from practical viewpoints. In this letter, we determine the maximum number of MOLS among a known class of Latin squares defined by weighted sums. We also mention some known property of Latin squares interpreted via the relation to secret sharing and a connection of Takeuti-Adachi\u27s scheme to Shamir\u27s secret sharing scheme

EMG activity during 2000 m rowing

This study aimed to clarify the changes in the activity of the trunk and lower limb muscles during 2000-m rowing. Ten male rowers performed a 2000-m race simulation on a rowing ergometer. Electromyography results of the abdominal muscles, back muscles, gluteus maximus (GMax), biceps femoris (BF), and rectus femoris (RF) were recorded. The electromyographic activity during the three strokes after the start (initial stage), at 1000m (middle stage), and before the end (final stage) were analyzed. From the handle position, the rowing motion was divided into five phases (early-drive, middle-drive, late-drive, early-recovery, and late-recovery). The peak activities of the abdominal muscles, back muscles, GMax, and BF in each stroke of the rowing motion were delayed at the middle and final stages compared to the initial stage (P < 0.05). The peak activity of the RF was observed in the late-drive phase at the initial stage, whereas a high RF activity was observed in the middle-drive phase at the middle and final stages (P < 0.05). Considering the results of the activity of the back muscles and RF, RF muscular endurance enhancement may lead to a decrease in the load on the back muscles and help prevent muscular low back pain in rowers