CONTEXT: In older adults, loss of mobility due to sarcopenia is exacerbated in men with low serum T. T replacement therapy is known to increase muscle mass and strength, but the effect of weekly (WK) vs monthly (MO) administration on specific fiber types is unknown. OBJECTIVE: To determine the efficacy of WK vs MO T replacement on the size and functional capacity of individual fast and slow skeletal muscle fiber types. DESIGN, SETTING, AND PATIENTS: Subjects were randomized into a 5-month, double-blind, placebo-controlled trial. All subjects (ages, 61-71 y) were community-dwelling men who had T levels < 500 ng/dL. INTERVENTION: Subjects were dosed weekly for 5 months, receiving continuous T (WK, n = 5; 100 mg T enanthate, im injection), monthly cycled T (MO, n = 7; alternating months of T and placebo), or placebo (n = 7). Muscle biopsies of the vastus lateralis were obtained before and after treatment. MAIN OUTCOME MEASURES: Main outcomes for individual slow and fast fibers included fiber diameter, peak force (P0), rate of tension development, maximal shortening velocity, peak power, and Ca(2+) sensitivity. RESULTS: Both treatments increased fiber diameter and peak power, with WK treatment 5-fold more effective than MO in increasing type I fiber P0. WK effects on fiber diameter and force were 1.5-fold higher in slow fibers compared to fast fibers. In fast type II fibers, diameter and P0 increased similarly between treatments. The increased power was entirely due to increased fiber size and force. CONCLUSIONS: In conclusion, T replacement effects were fiber-type dependent, restricted to increases in cell size, P0, and peak power, and dependent on the paradigm selected (WK vs MO).
RCT Entities:
CONTEXT: In older adults, loss of mobility due to sarcopenia is exacerbated in men with low serum T. T replacement therapy is known to increase muscle mass and strength, but the effect of weekly (WK) vs monthly (MO) administration on specific fiber types is unknown. OBJECTIVE: To determine the efficacy of WK vs MO T replacement on the size and functional capacity of individual fast and slow skeletal muscle fiber types. DESIGN, SETTING, AND PATIENTS: Subjects were randomized into a 5-month, double-blind, placebo-controlled trial. All subjects (ages, 61-71 y) were community-dwelling men who had T levels < 500 ng/dL. INTERVENTION: Subjects were dosed weekly for 5 months, receiving continuous T (WK, n = 5; 100 mg T enanthate, im injection), monthly cycled T (MO, n = 7; alternating months of T and placebo), or placebo (n = 7). Muscle biopsies of the vastus lateralis were obtained before and after treatment. MAIN OUTCOME MEASURES: Main outcomes for individual slow and fast fibers included fiber diameter, peak force (P0), rate of tension development, maximal shortening velocity, peak power, and Ca(2+) sensitivity. RESULTS: Both treatments increased fiber diameter and peak power, with WK treatment 5-fold more effective than MO in increasing type I fiber P0. WK effects on fiber diameter and force were 1.5-fold higher in slow fibers compared to fast fibers. In fast type II fibers, diameter and P0 increased similarly between treatments. The increased power was entirely due to increased fiber size and force. CONCLUSIONS: In conclusion, T replacement effects were fiber-type dependent, restricted to increases in cell size, P0, and peak power, and dependent on the paradigm selected (WK vs MO).
Authors: Walter R Frontera; Virginia A Hughes; Lisa S Krivickas; Sang-Kyu Kim; Mona Foldvari; Ronenn Roubenoff Journal: Muscle Nerve Date: 2003-11 Impact factor: 3.217
Authors: J J Widrick; J G Romatowski; J L Bain; S W Trappe; T A Trappe; J L Thompson; D L Costill; D A Riley; R H Fitts Journal: Am J Physiol Date: 1997-11
Authors: Melinda Sheffield-Moore; E Lichar Dillon; Shanon L Casperson; Charles R Gilkison; Douglas Paddon-Jones; William J Durham; James J Grady; Randall J Urban Journal: J Clin Endocrinol Metab Date: 2011-08-24 Impact factor: 5.958
Authors: R H Fitts; J G Romatowski; J R Peters; D Paddon-Jones; R R Wolfe; A A Ferrando Journal: Am J Physiol Cell Physiol Date: 2007-04-04 Impact factor: 4.249
Authors: Shalender Bhasin; Linda Woodhouse; Richard Casaburi; Atam B Singh; Ricky Phong Mac; Martin Lee; Kevin E Yarasheski; Indrani Sinha-Hikim; Connie Dzekov; Jeanne Dzekov; Lynne Magliano; Thomas W Storer Journal: J Clin Endocrinol Metab Date: 2004-11-23 Impact factor: 5.958
Authors: J J Widrick; K M Norenberg; J G Romatowski; C A Blaser; M Karhanek; J Sherwood; S W Trappe; T A Trappe; D L Costill; R H Fitts Journal: J Appl Physiol (1985) Date: 1998-11
Authors: Meghan E Downs; Jessica M Scott; Lori L Ploutz-Snyder; Robert Ploutz-Snyder; Elizabeth Goetchius; Roxanne E Buxton; Christopher P Danesi; Kathleen M Randolph; Randall J Urban; Melinda Sheffield-Moore; E Lichar Dillon Journal: Life Sci Space Res (Amst) Date: 2020-05-20