• ▶ muscle-tendon stiff ness • ▶ infl ammatory response • ▶ injury • ▶ therapeutic modality Instrument-assisted Soft Tissue Mobilization: Eff ects on the Properties of Human Plantar Flexorstion following eccentric exercise may be important components for the recovery of muscle tissue [ 20 ] . Though this research provides the most recent mechanistic example of the response to soft tissue mobilization in an animal model, the physiological diff erences to that of human subjects may limit its clinical applicability [ 11 , 35 ] . In contrast, the research fi ndings on IASTM often describe clinical markers such as range of motion (ROM) and functional measures, but are not derived from randomized controlled studies [ 15 ] . Collectively, however, it appears that soft tissue mobilization therapies may play a role in reducing infl ammation [ 6 ] . The purpose of this project was to evaluate the eff ects of IASTM on intramuscular infl ammation, pain, ROM and strength following muscle damage in a randomized controlled laboratory experiment. Materials and Methods ▼ Subjects11 healthy men (mean ± SD age = 23 ± 3 years; stature = 181 ± 7 cm; mass = 83 ± 11 kg) volunteered for this investigation. Each participant was screened Introduction ▼ According to the marketing information for Graston Technique ® , a form of instrument-assisted soft tissue mobilization (IASTM), more than 16 000 clinicians currently employ this technique for treating soft tissue ailments [ 17 ] . This does not include the number of clinicians and alternative medicine providers utilizing other forms of IASTM techniques such as sound-assisted soft tissue mobilization (SASTM), ASTYM ® , GuaSha, or others. Interestingly, the ability of IASTM to ameliorate loss of function, pain and infl ammation has yet to be clarifi ed. There are several physiological hypotheses as to how soft tissue mobilization works. These include increased blood fl ow, increased lymphatic drainage of toxins, reduced tissue stiff ness, alteration in neuromuscular activity and a decreased infl ammatory response [ 48 ] . However, the current literature fails to support these claims. Recently, studies have evaluated the eff ects of soft tissue mobilization on the recovery of muscular attributes following eccentric exercise-induced muscle damage [ 13 , 14 ] . Interestingly, it has been demonstrated that the intensity of the compressive load and the timing of applica-

It is suggested that firing rate characteristics of motor units (MUs) are influenced by the physical properties of the muscle. However, no study has correlated MU firing rates at recruitment, targeted force, or derecruitment with the contractile properties of the muscle in vivo. Twelve participants (age = 20.67 ± 2.35 yr) performed a 40% isometric maximal voluntary contraction of the leg extensors that included linearly increasing, steady force, and decreasing segments. Muscle biopsies were collected with myosin heavy chain (MHC) content quantified, and surface electromyography (EMG) was recorded from the vastus lateralis. The EMG signal was decomposed into the firing events of single MUs. Slopes and y-intercepts were calculated for 1) firing rates at recruitment vs. recruitment threshold, 2) mean firing rates at steady force vs. recruitment threshold, and 3) firing rates at derecruitment vs. derecruitment threshold relationships for each subject. Correlations among type I %MHC isoform content and the slopes and y-intercepts from the three relationships were examined. Type I %MHC isoform content was correlated with MU firing rates at recruitment (y-intercepts: r = -0.577; slopes: r = 0.741) and targeted force (slopes: r = 0.853) vs. recruitment threshold and MU firing rates at derecruitment (y-intercept: r = -0.597; slopes: r = 0.701) vs. derecruitment threshold relationships. However, the majority of the individual MU firing rates vs. recruitment and derecruitment relationships were not significant (P > 0.05) and, thus, revealed no systematic pattern. In contrast, MU firing rates during the steady force demonstrated a systematic pattern with higher firing rates for the lower- than higher-threshold MUs and were correlated with the physical properties of MUs in vivo.

Evidence suggests lymphocyte proliferation is suppressed following acute bouts of exercise, with exercise lasting longer than one hour having a greater magnitude of effect regardless of exercise intensity. Variations in observed effect sizes across intensity, duration, and competitive environment further highlight our need to acknowledge the impact of study designs in advancing our understanding of exercise immunology.

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The majority of the motoneuron pool had greater FRDEREC than FRREC , however, individuals with higher type I %MHC had a greater propensity to have MUs with FRREC > FRDEREC as indicated by the slope values. Overall, the contractile properties of the muscle (MHC) could partially explain the differences in MU firing rates at de-recruitment relative to recruitment. Thus, suggesting the fatigability of the muscle influences the alterations in MU firing rates from recruitment to de-recruitment.