Prediction of muscle fiber composition using multiple repetition testing

Abstract

Direct determination of muscle fiber composition is invasive and expensive, with indirect methods also requiring specialist resources and expertise. Performing resistance exercises at 80% 1RM is suggested as a means of indirectly estimating muscle fiber composition, though this hypothesis has never been validated against a direct method. The aim of the study was to investigate the relationship between the number of completed repetitions at 80% 1RM of back squat exercise and muscle fiber composition. Thirty recreationally active participants’ (10 females, 20 males) 1RM back squat load was determined, before the number of consecutive repetitions at 80% 1RM was recorded. The relationship between the number of repetitions and the percentage of fast-twitch fibers from vastus lateralis was investigated. The number of completed repetitions ranged from 5 to 15 and was independent of sex, age, 1RM, training frequency, training type, training experience, BMI or muscle fiber cross-sectional area. The percentage of fast-twitch muscle fibers was inversely correlated with the number of repetitions completed (r = –0.38, P = 0.039). Participants achieving 5 to 8 repetitions ( n = 10) had significantly more fast-twitch muscle fibers (57.5 ± 9.5 vs 44.4 ± 11.9%, P = 0.013) than those achieving 11–15 repetitions ( n = 11). The remaining participants achieved 9 or 10 repetitions ( n = 9) and on average had equal proportion of fast- and slow-twitch muscle fibers. In conclusion, the number of completed repetitions at 80% of 1RM is moderately correlated with muscle fiber composition.

Association of muscle fiber composition with health and exercise-related traits in athletes and untrained subjects

“…We report novel associations of STMF% and with heart rate, chest depth and fracture risk and support previous relationships of this trait with age, endurance ability and blood pressure. Once replicated in independent cohorts, measures of resting heart rate, chest depth and self-reported tolerance to long distances could be combined with additional variables, such as consecutive back squat repetitions at 80% 1RM [ 3 ], to investigate whether the indirect estimation of STMF% can be improved using multiple non-invasive measures. An ability to indirectly estimate muscle fiber composition with confidence would be particularly useful to practitioners working in health, exercise and professional sport, where there is limited access to direct assessment of muscle fiber composition.…”

“…Slow-twitch muscle fibers (STMF) have higher oxidative capacity than fast-twitch muscle fibers (FTMF), which have higher glycolytic enzyme activity [ 2 ] and faster maximal shortening velocities that contribute to superior maximal power [ 1 ]. Subjects with a greater proportion of STMF generally complete a greater number of repetitions at 80% 1 repetition maximum (1RM) during resistance training than individuals with increased proportion of FTMF [ 3 ].…”

Impact of Training Protocols on Lifting Velocity Recovery in Resistance Trained Males and Females

“…Women have been shown to present with a higher type-I fiber area, higher concentrations of circulating estrogens, higher muscle perfusion, a lower reliance on the anaerobic metabolism, and be less sensitive to central fatigue [9,11,12]. While many of these factors have indeed been associated with fatigability and/or recovery [9,27,28], they or their association with recovery and/or fatigability are subject to change dependent on the contraction type, training intensity, training status, hormonal status, etc. [9,[29][30][31].…”

Muscle architecture a new dimension of talent identification: A mini review

“…Campion, 1979; Suter, E., W. Herzog, J. Sokolosky, J.P. Wiley, 1993) [6,10,11,12,30] . Accurate determination of muscle fiber composition is invasive and expensive, while in-direct measurement approaches necessitate the use of specialized resources and skills to be effective (Hall et al, 2021) [13] . Tensiomyography (TMG) is a new technique for determining the type of muscle fibers on the basis of the contractile properties of skeletal muscle fibers.…”