Jose A. Arevalo

Skeletal muscle fatigability and myosin heavy chain fiber type in resistance trained men.

Abstract Bagley, JR, McLeland, KA, Arevalo, JA, Brown, LE, Coburn, JW, and Galpin, AJ. Skeletal muscle fatigability and myosin heavy chain fiber type in resistance trained men. J Strength Cond Res 31(3): 602–607, 2017—Forty years ago, Thorstensson and Karlsson in 1976 described the link between muscle fatigability and fiber type, finding that more fast-twitch fibers were associated with a quicker onset of quadriceps fatigue. This provided the foundation for the Classic Thorstensson Test of fatigability and subsequent noninvasive fiber type prediction equation. This equation was developed with data from recreationally active (REC) men but has been implemented in participants with heterogeneous physical activity/exercise backgrounds. The accuracy of this approach in resistance trained (RET) men has not been established. Moreover, muscle fiber typing techniques have evolved considerably since this seminal work. Therefore, we reexamined this relationship using RET men and a more sensitive fiber typing method (single fiber myosin heavy chain [MHC] isoform classification). Fifteen RET men (age = 24.8 ± 1.3 years) performed maximal knee extensions (via isokinetic dynamometry) to determine peak torque (PT) and quadriceps fatigue percentage (FP) after 30 and 50 repetitions. Vastus lateralis (VL) single fiber MHC type was determined and fibers were grouped as %Fast (expressing MHC IIa, IIa/IIX, or IIx; no MHC I containing fibers). Resistance trained men exhibited 46% greater PT (RET = 207 ± 28 N·m vs. REC = 130 ± 8 N·m) and 28% more %Fast (RET = 61 ± 4% vs. REC = 44 ± 4%) than REC men. Additionally, RET men had a relatively homogeneous FP (64 ± 1%) ranging from 53 to 72%. No relationship was found between FP and MHC fiber type (R 2 = 0.01, p > 0.05). The Classic Thorstensson Test may not accurately estimate VL fiber type composition in RET men, highlighting the (a) unique phenotypical/functional adaptations induced by chronic RET and (b) the need for more sensitive cellular/molecular analyses in RET muscle.

Bench press and pushup repetitions to failure with equated load

The bench press and pushup are commonly used for training upper body muscular strength and endurance. Although they are often used interchangeably, differences between the two relative to body mass load are unknown. Furthermore, sex differences may exist due to anthropometric body mass specificity. The purpose of this study was to evaluate the relationship between the pushup and bench press when performing repetitions to failure with an equated load. On day 1, 25 recreationally trained subjects (16 men, age = 23.00 ± 2.36 years, height = 178.19 ± 9.61 cm, mass = 74.80 ± 13.44 kg; 9 women, age = 23.11 ± 2.71 years, height = 160.78 ± 5.95 cm, mass = 53.63 ± 5.60 kg), performed a one repetition maximum bench press and an isometric pushup on a force plate to determine bodyweight load supported in both the up and down positions. Grip width on the bench press was measured as the distance between middle fingers and was used for hand placement during pushups. For the down position, a safety squat device was placed on the right triceps to signal that the upper arms were parallel to the ground, while for the up position, triceps were perpendicular to the floor. Days 2 and 3 consisted of performing repetitions to failure for either the bench press or pushup exercise with a load that was equal to the average relative bodyweight force of the up and down pushup positions. For the pushup, subjects followed a 60 beats per minute tempo and the test was terminated if they failed to complete a full repetition; they could not maintain cadence or there were three faults in form. For the bench press, they followed the same 60 s tempo and the test was terminated if they failed to complete a full repetition or could not maintain cadence. A 2 (exercise: bench press, pushup) × 2 (sex: men, women) mixed factor ANOVA demonstrated no interaction, but there were significant (P < 0.05) main effects for exercise and sex where more repetitions were performed in the pushup (19.36 ± 11.68 reps) than the bench press (11.40 ± 8.38 reps) exercise. Also, men performed significantly more repetitions to failure (men =20.22 ± 8.20 reps, women = 6.78 ± 5.69 reps). For combined sexes, there was a significant (P < 0.05), strong relationship (r = 0.82) between bench press and pushup repetitions to failure. For men, there was a significant (P < 0.05), strong relationship (r = 0.81), while for women, there was a moderate relationship (r = 0.76). Men had significantly (P < 0.05) greater bench press one repetition maximum (men = 99.29 ± 23.98 kg, women = 42.17 ± 8.88 kg), percentage of body mass supported as an average of the up and down positions (men = 74.33 ± 2.57%, women = 69.70 ± 2.63%) and bench press one repetition maximum relative to their body mass (men = 1.32 ± 0.22%, women = 0.79 ± 0.13%). The bench press and pushup are two distinct upper body exercises for repetitions to failure due to upper body musculature and body position sex differences. Choice of the pushup or bench press exercise should be based on training goal and sex.