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C-12 Free Communication/Slide - Older Adults Thursday, May 30, 2019, 9: 30 AM - 11: 30 AM Room: CC-202C

Age-related Differences in Rectus Femoris Muscle Size and Hip Flexion Maximal and Rapid Torque Characteristics

1188 May 30 10:00 AM - 10:15 AM

Palmer, Ty B.; Palmer, Bailey M.

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Medicine & Science in Sports & Exercise: June 2019 - Volume 51 - Issue 6S - p 311-312
doi: 10.1249/01.mss.0000561443.12582.df
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Previous studies have reported that decreases in muscle size of the rectus femoris (RF) may contribute to age-related deficits in leg extension strength. However, we are aware of no studies that have examined the contribution of RF muscle size to age-related differences in hip flexion strength, and more specifically, the age-related differences in maximal and rapid torque characteristics.

PURPOSE: To determine the effects of age on RF muscle size (cross-sectional area [CSA]) and hip flexion maximal and rapid torque characteristics in young and old men.

METHODS: Fifteen young (age = 25 ± 3 yr; body mass = 86 ± 17 kg; height = 176 ± 5 cm) and 15 old (73 ± 4 yr; 83 ± 10 kg; 173 ± 6 cm) men underwent two diagnostic ultrasound assessments followed by two isometric maximal voluntary contractions (MVCs) of the hip flexors on an isokinetic dynamometer. RF CSA (cm2) was measured on the right leg using a portable B-mode ultrasound imaging device and linear-array probe. For each MVC, participants laid supine with the knee- and ankle-joints immobilized using custom-built stabilizing apparatuses. All MVCs were performed on the right leg at a hip joint angle of 20° above the horizontal plane. Participants were instructed during each MVC to flex the thigh at the hip “as hard and fast as possible” for 3-4 s. Isometric MVC peak torque (PT; Nm) was calculated as the highest mean 500 ms epoch during the entire 3-4 s MVC plateau. Rate of torque development (RTD; Nm·s-1) was calculated as the peak of the first derivative of the torque signal.

RESULTS: There were no differences between the young and old men for body mass (P = 0.624) and height (P = 0.156). The old men exhibited lower CSA (old = 10.05 ± 1.82 cm2; young = 12.16 ± 2.59 cm2; P = 0.015), PT (old = 117.22 ± 17.42 Nm; young = 144.16 ± 29.72 Nm; P = 0.005), and RTD (old = 1129.62 ± 374.77 Nm·s-1; young = 1718.26 ± 633.04 Nm·s-1; P = 0.005) than the young men. Significant relationships were observed between CSA and PT (r = 0.520; P = 0.003) and RTD (r = 0.534; P = 0.002).

CONCLUSION: These findings demonstrated that RF muscle size and hip flexion PT and RTD decrease in old age. The significant relationships observed between CSA and PT and RTD in the young and old men perhaps suggest that these age-related declines in RF muscle size may play an important role in the lower hip flexion maximal and rapid torque values observed in older adults.

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