Carrying Heavy Shopping Bags and Muscle Function

Takei Back Strength Dynamometer (T.K.K. 5002 BACK-A Type-3) used to measure back strength to the nearest 1 kg. Measurements taken with the legs, back and arms straight and the torso flexed to 30 degrees at the hip with the handle held in a natural grip. Participants instructed to gradually pull as hard as they could on the handle in order to raise the upper part of their body without bending their knees. Three trials performed with the maximum value used in the analysis.

Assessed using a countermovement jump with hands on hips. Participants instructed to crouch into a squat position and then jump as high as possible with legs fully extended and landing on the same spot with knees extended and feet together. After a familiarisation attempt, participants to perform three countermovement jumps and the maximum peak power used in the analysis. Jump height and flight time calculated using Microgate Optojump Next software version 1.10.5.0 connected to photoelectric bars RX10 and TX10 (Microgate Optojump Next, Bolzano, Italy) placed parallel to each other.

Jump height derived from the equation: H = g×t2/8 (H = the jump height (m), t = jump flight time (seconds) and g = acceleration due to gravity (9.81 m/s-2))

Assessed using a countermovement jump with hands on hips. Participants instructed to crouch into a squat position and then jump as high as possible with legs fully extended and landing on the same spot with knees extended and feet together. After a familiarisation attempt, participants to perform three countermovement jumps and the maximum peak power used in the analysis. Jump height and flight time calculated using Microgate Optojump Next software version 1.10.5.0 connected to photoelectric bars RX10 and TX10 (Microgate Optojump Next, Bolzano, Italy) placed parallel to each other.

Peak Power calculated using the Sayers equation: Peak Power (Watts) = 60.7 × jump height (cm) + 45.3 × body mass (kg) - 2055

Endurance assessed by a 60 second sit to stand test using a 46.5cm high, straight-backed chair with a hard seat and no arm rests. From a seated position with hands on shoulders and arms crossed across the chest, participants instructed to stand up from the chair until their legs were completely straight, then sit back down again (one complete sit to stand) as many times as possible in 60 seconds. The number of complete sit to stands used in the analysis.

Jamar hydraulic hand dynamometer in handle position II used to measure grip strength to the nearest 1 kg. Measurements taken with the participant seated with feet flat on the floor, elbow flexed 90 degrees by their side and with the wrist just over the end of the arm of the chair in a neutral position (thumbs-up position). Participants instructed to squeeze as hard as possible until the needle stopped rising with the verbal encouragement of "squeeze, squeeze, squeeze and relax". Three trials performed on each side, alternately, with the maximum value used in the analysis in accordance with the Southampton protocol

Assessed using a Body Composition Analyzer Type BC-418 MA (Tanita Corporation, Tokyo, Japan) to determine whole body bioimpedance between the hands and feet by applying a constant current of 90 microamps at 50kHz through the body. Measurements taken in the standing position with bare feet placed on the footplate electrodes and the hand grip electrodes held by the side of the body. Whole body impedance used to derive skeletal muscle mass.

The number of complete corridor lengths walked with the shopping bags in 15 minutes was recorded for those in the intervention group.

Perceived exertion was measured using the Borg Rating of Perceived Exertion scale (RPE) [44] from 6-20, with 20 meaning the harderst exertion and 6 the least exertion at the end of each 15-minute carry for those in the intervention group.