Characteristics of titin in strength and power athletes

Abstract

The purpose of this investigation was to identify characteristics of the muscle protein titin in different athletic populations with increased levels of strength and power relative to non-athletes. Subjects fell into one of four groups: (1) non-athletes (NA) ( n=5), (2) weightlifters (WL) (n=5), (3) powerlifters (PL) (n=5), (4) sprinters (S) (n=5). A one repetition maximum in the squat exercise was performed to assess strength. In addition, countermovement vertical jump trials were performed to assess power capabilities. Peak power (W(peak)) was calculated for the vertical jumps from force plate measurements. From gel electrophoresis analyses of muscle samples, titin-1 (T1) and titin-2 (T2) protein bands were identified, quantified and expressed relative to each other. In addition the relative mobility (R(f)) of T1 and T2 was determined as an estimate of molecular weight. The NA group [%T1=47.8 (5.1), %T2=52.2 (5.1), mean (SE)] had lower T1 and higher T2 percentages than WL [%T1=62.3 (6.6), %T2=37.7 (6.6)], PL [%T1=66.8 (5.0), %T2=33.2 (5.0)] and S [%T1=65.9 (4.9), %T2=34.1 (4.9)] groups (P< or =0.10, preliminary investigation into titin and exercise justifies more liberal alpha level). No significant differences were found in R(f) of T1 or T2 between the groups. This investigation has shown that there is a differential expression of titin protein bands in competitive athletes with increased levels of strength and power in comparison to untrained non-athletic individuals. Some relationships between titin characteristics and athletic performance were observed; however, no conclusions can be made based on these data as to the contribution of titin to strength or power capabilities.

Effects of Eccentric Exercise on Joint Stiffness and Muscle Connectin (Titin) Isoform in the Rat Hindlimb

“…Although measuring the absolute content of connectin within fibers is difficult due to its large molecular mass, its isoform composition (α:β) has been thought to be an indicator for the protein metabolism of connectin [20,21,30]. It has been shown that the relative content of β-connectin (β/α+β) is larger in fast type II fibers than in slow type I fibers [30], and the smaller β/α+β may provide larger passive resistance to stretch.…”

“…Several studies have investigated the relationship between resistance training and connectin isoform composition in human muscle. Although it has been shown that, in humans, exercise training did not cause a considerable change in the muscle connectin isoform composition [20], it has also been shown that β-connectin isoform percentage tends to be lower in competitive athletes than in non-athletes [21]. Therefore, a prolonged period of strenuous exercise training may cause any change in β-connectin, thereby affecting joint stiffness.…”

Effects of power training on muscle structure and neuromuscular performance

“…Moritani and deVries (1979) have demonstrated that in high intensity strength training the neural factors dominate in strength development at the three first weeks of training, while the hypertrophic factors start to play a major role after this time. In power training, increases in muscle power capabilities have been observed with coincidental changes in neural factors ; however, possible muscle structural adaptations have not been clearly identified (Ha¨kkinen et al, 1985;McBride et al, 2003;McGuigan et al, 2003).…”

“…While myosin is directly involved in the force production processes of muscle contraction, titin, which is a large protein acting as anchor between the z-lines and myosin within the sarcomere, is thought to have effects on the elastic characteristics of muscle fibers (Tskhovrebova & Trinick, 2002). It is possible that improvements in muscle power could be related to shifts in MHC or titin isoforms, because both of them contribute to the force production (Staron et al, 1990;McBride et al, 2003). Andersen and Aagaard (2000) have shown that the 3 months of heavy resistance training decreases the amount of MHC IIX content, while MHC IIA content increases.…”

Effects of an eccentric training programme on hamstring strain injuries in women football players

“…Sarcomeres that are exposed to greater strains may express titins with larger elastic segments. In fact, sprinters expressed a greater percentage of titin-1 isoforms than non-athletes [22]. It is possible that the titin is capable of storing and releasing elastic energy [18], and consequently, RSHS could be reduced.…”