Massimiliano Ditroilo

The effectiveness of two novel techniques in establishing the mechanical and contractile responses of biceps femoris

Portable tensiomyography (TMG) and myotonometry (MMT) devices have been developed to measure mechanical and contractile properties of skeletal muscle. The aim of this study was to explore the sensitivity of the aforementioned techniques in detecting a change in passive mechanical properties of the biceps femoris (BF) muscle as a result of change in knee joint angle (i.e. muscle length). BF responses were assessed in 16 young participants (23.4 ± 4.9 years), at three knee joint angles (0°, 45° and 90°), for maximal isometric torque (MIT) along with myo-electrical activity. Contractile and mechanical properties were measured in a relaxed state. Inter-day reliability of the TMG and MMT was also assessed. MIT changed significantly (p < 0.01) across the three angles, so did stiffness and other parameters measured with MMT (p < 0.01). Conversely, TMG could detect changes only at two knee angles (0° and 45°, p < 0.01), when there is enough tension in the muscle. Reliability was overall insufficient for TMG whilst absolute reliability was excellent (coefficient of variation < 5%) for MMT. The ability of MMT more than TMG to detect an inherent change in stiffness can be conceivably exploited in a number of clinical/therapeutic applications that have to do with unnatural changes in passive muscle stiffness.

Physiological responses to fitness activities: a comparison between land-based and water aerobics exercise.

This study compared the heart rate (HR) and blood lactate (BL) responses in young healthy women performing the same routine of aerobics exercise in 3 different conditions: on land, in shallow water (0.8 m), and in deep water (1.4 m). The average age and body mass index (BMI) of the group were 27.4 years and 22.6 kg·m−2, respectively. The highest HR and BL values were reached during land aerobics (median HR values were 138.0 and 161.5 b·min−1, and lactate values were 3.10 and 5.65 mmol·L−1 at slow and at faster pace, respectively). These parameters were progressively reduced going from shallow water (121.5 and 154.0 b·min−1, 1.75 and 3.15 mmol·L−1) to deep water (97.5 and 113.5 b·min−1, 1.70 and 1.75 mmol·L−1). The HR measured as percentage of maximum HR varied from 48.43% to 77.53% depending on the water depth and the pace. These data indicate that exercise in water significantly reduces HR and BL production compared with the same exercise performed on land.

Assessment of eccentric exercise-induced muscle damage of the elbow flexors by tensiomyography

Exercise induced muscle damage (EIMD) impairs maximal torque production which can cause a decline in athletic performance and/or mobility. EIMD is commonly assessed by using maximal voluntary contraction (MVC), creatine kinase (CK) and muscle soreness. We propose as an additional technique, tensiomyography (TMG), recently introduced to measure mechanical and muscle contractile characteristics. The purpose of this study was to determine the validity of TMG in detecting changes in maximal torque following EIMD. Nineteen participants performed eccentric elbow flexions to achieve EIMD on the non- dominant arm and used the dominant elbow flexor as a control. TMG parameters, MVC and rate of torque development (RTD) were measured prior to EIMD and repeated for another six consecutive days. Creatine kinase, muscle soreness and limb girth were also measured during this period. Twenty four hours after inducing EIMD, MVC torque, RTD and TMG maximal displacement had significantly (p<0.01) declined by 37%, 44% and 31%, respectively. By day 6 MVC, RTD and TMG recovered to 12%, 24% and 17% of respective pre-EIMD values. In conclusion, as hypothesised TMG maximal displacement significantly followed other standard EIMD responses. This could therefore be useful in detecting muscle damage from impaired muscle function and its recovery following EIMD.

Concurrent Validity of Vertical Jump Performance Assessment Systems

Abstract Castagna, C, Ganzetti, M, Ditroilo, M, Giovannelli, M, Rocchetti, A, and Manzi, V. Concurrent validity of vertical jump performance assessment systems. J Strength Cond Res 27(3): 761–768, 2013—The aim of this study was to examine the concurrent validity of 2 portable systems for vertical jump (VJ) assessment under field conditions. The VJ flight times assessed using an optical mat (Optojump) and an accelerometer-based (Myotest) system were compared with that of a force platform. The flight times recorded during a countermovement jump (CMJ) were collected from 20 rugby players (n = 86 jumps) concurrently using the 3 tracking systems. Significant bias between the Force platform and either the Optojump (bias = 0.006 ± 0.007; 95% confidence interval [CI] 0.004–0.007 seconds) and Myotest (bias = −0.031 ± 0.021; 95% CI 0.035 to −0.026s; p < 0.0001) occurred. A nearly perfect correlation was found between force platform and Optojump (r = 0.99; 95% CI 0.098–0.99; p < 0.0001). Force platform and Myotest (r = 0.89; 95% CI 0.084–0.93; p < 0.0001) flight times showed very large association. Difference between Optojump and Myotest systems was significant (−0.036 ± 0.021 seconds; 95% CI −0.041 to −0.032; p < 0.0001), which results in Myotest mean flight time being approximately 7.2% longer than the Optojump flight time. The association between Optojump and Myotest was nearly perfect (r = 0.91, 95% CI 0.86–0.94; p < 0.0001). This study showed that the Optojump and Myotest systems possess convergent validity and can be successfully used under field conditions to assess VJ while performing a CMJ. However, caution should be exercised when interpreting data obtained from different portable systems for field measurement.

Effects of age and limb dominance on upper and lower limb muscle function in healthy males and females aged 40–80 years

Abstract This study investigated the effects of gender, age, and dominance on upper and lower limb muscle function. One hundred and fifty-two males and females aged 20–30 and 40–80 years were recruited. Maximal voluntary isometric strength (MVC) and rate of force development (RFD) of the knee extensor muscles, and handgrip MVC were measured bilaterally as indicators of lower and upper limb muscle function, respectively. In both sexes, significant main effects were found for age (knee extension MVC, RFD, and handgrip MVC) and limb dominance (handgrip MVC). Men exhibited a steeper age-related decline in muscle function than women, particularly in the lower limb [dominant limb: knee extension MVC −56% (men) vs. −35% (women); handgrip MVC −30% (men) vs. −26% (women); RFD −67% (men) vs. −47% (women); non-dominant limb: knee extension MVC −49% (men) vs. −36% (women); handgrip MVC −26% (men) vs. −24% (women); RFD −62% (men) vs. −44% (women)]. Although men showed a higher rate of decline in muscle function, in absolute terms they demonstrated better muscle function than women in all age groups, which has important implications for independence and quality of life. A clear asymmetry in muscle function was evident in both sexes only for handgrip MVC.

Muscle Stiffness and Rate of Torque Development during Sprint Cycling

PURPOSE Crank torque (CT) application and rate of CT development (RCTD) are important considerations in sprint cycling. The stiffness of the musculotendinous unit is related to the isometric rate of torque development (RTD); however, this relationship has yet to be examined in sprint cycling. METHODS Maximal isometric torque (MIT) and isometric RTD of the quadriceps were assessed in 21 trained male cyclists (28.7 +/- 9.5 yr, 1.74 +/- 0.08 m, and 67.5 +/- 7.2 kg). Unilateral musculoarticular (MA) stiffness of the quadriceps was quantified using an oscillation test. Further, the participants performed a maximal 6-s sprint to assess peak power output (POpeak), peak CT (CTpeak), peak RCTD (RCTDpeak), and the crank angles associated with CTpeak and RCTDpeak. Participants were ranked on MA stiffness properties and were divided into a relatively stiff group (SG) and a relatively compliant group (CG). RESULTS The SG displayed a significantly higher MA stiffness than the CG (P < 0.05). Furthermore, the SG reported significantly elevated MIT (27%), RTD (26%), and RCTDpeak (16%) when compared with the CG (P < 0.05), along with trends for increased POpeak (7%) and CTpeak (8%). The angles at CTpeak and RCTDpeak were 7% and 12% lower for the SG, respectively (P < 0.05). MA stiffness was significantly correlated with RCTDpeak, MIT, RTD, and POpeak. CONCLUSIONS Higher stiffness is related to superior RCTDpeak in trained cyclists during a single sprint. A significant proportion of the variance in RCTDpeak was attributed to MA stiffness (37%), which was of greater magnitude than the relationship between RCTDpeak and MIT. Furthermore, the lower CTpeak angle and RCTDpeak angle may contribute to a more rapid development of CT. Accordingly, MA stiffness seems to be an important consideration for sprint cycling.

A maximal isokinetic pedalling exercise for EMG normalization in cycling

An isometric maximal voluntary contraction (iMVC) is mostly used for the purpose of EMG normalization, a procedure described in the scientific literature in order to compare muscle activity among different muscles and subjects. However, the use of iMVC has certain limitations. The aims of the present study were therefore to propose a new method for the purpose of EMG amplitude normalization in cycling and assess its reliability. Twenty-three cyclists performed 10 trials of a maximal isokinetic protocol (MIP) on a cycle ergometer, then another four sub-maximal trials, whilst the EMG activity of four lower limbs muscles was registered. During the 10 trials power output (CV=2.19) and EMG activity (CV between 4.46 and 8.70) were quite steady. Furthermore, their maximal values were reached within the 4th trial. In sub-maximal protocol EMG activity exhibited an increase as a function of exercise intensity. MIP entails a maximal dynamic contraction of the muscles involved in the pedalling action and the normalization session is performed under the same biomechanical conditions as the following test session. Thus, it is highly cycling-specific. MIP has good logical validity and within-subject reproducibility. Three trials are enough for the purpose of EMG normalization in cycling.

Long-term stability of tensiomyography measured under different muscle conditions

Tensiomyography (TMG) is a technique utilised to measure mechanical and contractile properties of skeletal muscle. Aim of this study was to assess long-term stability of TMG across a variety of muscle conditions. Gastrocnemius Medialis of 21 healthy males was measured using TMG in rested conditions, after a warm-up, after a maximal voluntary contraction and after a fatigue protocol. Participants were re-tested on a second occasion 4weeks apart. Among the parameters examined, Contraction Time, Sustain Time and Delay time exhibited a good level of absolute reliability (CV=3.8-9.4%) and poor to excellent level of relative reliability (ICC=0.56-0.92). On the other hand, relative reliability was good to excellent for muscle Displacement (ICC=0.86-0.96), whereas its level of absolute reliability was questionable (CV=8.0-14.8%). Minimum detectable change was less than 20% in most conditions for the aforementioned parameters. Half-relaxation Time yielded overall insufficient reliability. In general, the level of reliability tended to increase after the maximal voluntary contraction and the fatigue protocol were administered, probably because of more controlled conditions preceding the measurement. Information about the long-term stability of TMG across different muscle conditions is essential when intervention studies are undertaken with an exercising population, particularly athletes.

Intra- and inter-session reliability of vertical jump performance in healthy middle-aged and older men and women

Abstract Despite its widespread use in performance assessment, the reliability of vertical jump in an ageing population has not been addressed properly. The aim of the present study was to assess intra- and inter-day reliability of countermovement jump in healthy middle-aged (55–65 years) and older (66–75 years) men and women. Eighty-two participants were recruited and asked to perform countermovement jumps on two different occasions interspersed by 4 weeks. The middle-aged groups exhibited excellent absolute reliability for flight height, jump height, peak force, peak power, peak force/body mass, and peak power/body mass, with coefficients of variation ranging from 2.9% to 7.2% in men and from 3.6% to 6.9% in women and moderate-to-high intraclass correlations (0.75 to 0.97 in men; 0.77 to 0.95 in women). The older groups displayed good coefficients of variation (4.2% to 10.8% in men and 3.4% to 9.5% in women), but the intraclass correlations were low-to-high (0.43 to 0.84 in men; 0.42 to 0.93 in women). Overall, intra-session reliability was higher than inter-session reliability. Peak power was by far the most consistent variable, whereas flight and jump height had the most marked variability. The minimum detectable change varied from 10.5% to 33%, depending on the variable examined, suggesting important implications for intervention studies.

Kinematic and electromyographic analysis of the Nordic Hamstring Exercise.

The Nordic Hamstring Exercise (NHE) has been introduced as a training tool to improve the efficiency of eccentric hamstring muscle contraction. The aim of this study was to perform a biomechanical analysis of the NHE. Eighteen participants (20.4±1.9years) performed two sets of five repetitions each of the NHE and maximal eccentric voluntary contraction (MEVC) of the knee flexors on an isokinetic dynamometer whilst knee angular displacement and electrical activity (EMG) of biceps femoris were measured. EMG was on average higher during the NHE (134.3% of the MEVC). During the forward fall of the NHE, the angle at which a sharp increase in downward velocity occurred varied between 47.9 and 80.5deg, while the peak knee angular velocity (pVelocity) varied between 47.7 and 132.8degs(-1). A significant negative correlation was found between pVelocity and peak EMG (r=-0.62, p<0.01) and EMG at 45deg (r=-0.75, p<0.01) expressed as a percentage of peak MEVC EMG. Some of the variables analyzed exhibited good to excellent levels of intra- and inter-session reliability. This type of analysis could be used to indirectly monitor the level of eccentric strength of the hamstring muscles while performing the NHE and potentially any training- or injury-related changes.