Psychophysical predictors of experimental muscle pain intensity following fatiguing calf exercise

Musculoskeletal pain affects approximately 20% of the population worldwide and represents one of the leading causes of global disability. As yet, precise mechanisms underlying the development of musculoskeletal pain and transition to chronicity remain unclear, though individual factors such as sleep quality, physical activity, affective state, pain catastrophizing and psychophysical pain sensitivity have all been suggested to be involved. This study aimed to investigate whether factors at baseline could predict musculoskeletal pain intensity to an experimental delayed onset of muscle soreness (DOMS) pain model. Demographics, physical activity, pain catastrophizing, affective state, sleep quality, isometric force production, temporal summation of pain, and psychophysical pain sensitivity using handheld and cuff algometry were assessed at baseline (Day-0) and two days after (Day-2) in 28 healthy participants. DOMS was induced on Day-0 by completing eccentric calf raises on the non-dominant leg to fatigue. On Day-2, participants rated pain on muscle contraction (visual analogue scale, VAS, 0-10cm) and function (Likert scale, 0–6). DOMS resulted in non-dominant calf pain at Day-2 (3.0±2.3cm), with significantly reduced isometric force production (P<0.043) and handheld pressure pain thresholds (P<0.010) at Day-2 compared to Day-0. Linear regression models using backward selection predicted from 39.3% (P<0.003) of VAS to 57.7% (P<0.001) of Likert score variation in DOMS pain intensity and consistently included cuff pressure pain tolerance threshold (P<0.01), temporal summation of pain (P<0.04), and age (P<0.02) as independent predictive factors. The findings indicate that age, psychological and central pain mechanistic factors are consistently associated with pain following acute muscle injury.

Association of Jumping Ability and Maximum Strength With Dive Distance in Swimmers

Purpose: The aim of the current study was to investigate the relationship between dive distance (DD) and countermovement jump (CMJ) height, track start CMJ height, countermovement broad jump (CMBJ) distance, track start broad jump distance, and isometric midthigh pull peak force and relative peak force. Methods: A total of 27 (11 female and 16 male) regional-national-international-standard swimmers (mean [SD]; age = 19.5 [5.5] y; mass = 69.3 [10.5] kg; height = 1.77 [0.09] m) performed 3 trials of a track start dive, CMJ, track start CMJ, CMBJ, track start broad jump, and isometric midthigh pull. Results: Data were separated into pooled (females and males combined), females, and males. Large to very large correlations were found between DD and all variables tested for pooled data (r = .554–.853, P < .001–.008), with DD-CMBJ displaying the highest correlation (r = .853, P < .001). CMBJ accounted for 70% of the variance in DD. Females demonstrated moderate nonsignificant correlations between DD isometric midthigh pull (r = .379, P < .125). Males demonstrated very large significant correlations between DD-CMJ (r = .761, P < .001). Conclusions: DD demonstrated strong correlations with jump performances and multijoint isometric force production in pooled data. Males showed stronger correlations than females due to being stronger and being able to perform the jumping/strength tasks to a higher standard. Enhanced jump performance and increased maximal force production may, therefore, enhance DD in swimmers.

Acute beetroot juice administration improves peak isometric force production in adolescent males

The purpose of this study was to examine the effects of acute beetroot juice (BR) administration on repeated sprint performance and isometric force production in adolescent males. Twelve male adolescents (age, 16.8 ± 1.0 years; height, 178.8 ± 9.2 cm; mass, 74.8 ± 12.5 kg; peak height velocity, 2.53 ± 1.2 years) participated in this double-blind, placebo-controlled, crossover designed study. Participants consumed 2 × 70 mL of BR (∼12.9 mmol NO3−; Beet It Sport) or a nitrate-depleted placebo (PL) at 2.5 h prior to performing isometric mid-thigh pulls (IMTP) and 4 repeated 20-s Wingate sprints interspersed with 4 min of rest. Sprint data were analyzed by a 2 × 4 (group × time) repeated-measures ANOVA while a dependent t test was used to compare conditions for IMTP peak force. A significant main effect for time (p < 0.05) was observed for peak power (PP), average power (Pavg), and fatigue index (FI) across sprints. Compared with sprint 1, sprint 4 resulted in significant decreases in PP (p < 0.000; −16.6%) and Pavg (p = 0.000; −21.8%) and FI was significantly elevated (p < 0.000; 15.2%). No significant group × time interactions were observed between conditions for PP (p = 0.402), Pavg (p = 0.479), or FI (p = 0.37). IMTP peak force was significantly higher (p = 0.004; 13.9%) following BR consumption compared with PL. The repeated sprint protocol resulted in significant fatigue while BR did not influence sprint performance. However, it appears BR administration may improve peak force production in adolescent males.

Spontaneous and α-adrenoceptor-induced contractility in human collecting lymphatic vessels require chloride

Human lymphatic vessels are myogenically active and respond to sympathetic stimulation. The role of various cations in this behavior has recently been investigated, but whether the anion Cl− is essential is unclear. With ethical approval and informed consent, human thoracic duct and mesenteric lymphatic vessels were obtained from surgical patients. Spontaneous or norepinephrine-induced isometric force production from isolated vessels was measured by wire myography; the transmembrane Cl− gradient and Cl− channels were investigated by substitution of extracellular Cl− with the impermeant anion aspartate and inhibition of Cl− transport and channels with the clinical diuretics furosemide and bendroflumethiazide as well as DIDS and 5-nitro-2-(3-phenylpropylamino)benzoic acid. The molecular expression of Ca2+-activated Cl− channels was investigated by RT-PCR, and proteins were localized using immunoreactivity. Spontaneous and norepinephrine-induced contractility in human lymphatic vessels was highly abrogated after Cl− substitution with aspartate. About 100–300 µM DIDS or 5-nitro-2-(3-phenylpropylamino)benzoic acid inhibited spontaneous contractile behavior. Norepinephrine-stimulated tone was furthermore markedly abrogated by 200 µM DIDS. Furosemide lowered only spontaneous constrictions, whereas bendroflumethiazide had nonspecific inhibitory effects. Consistent expression of transmembrane member 16A [TMEM16A (anoctamin-1)] was found in both the thoracic duct and mesenteric lymphatic vessels, and immunoreactivity with different antibodies localized TMEM16A to lymphatic smooth muscle cells and interstitial cells. The significant change in contractile function observed with inhibitors and anion substitution suggests that Cl− movement over the plasma membrane of lymphatic myocytes is integral for spontaneous and α-adrenoceptor-evoked contractility in human collecting lymphatic vessels. Consistent detection and localization of TMEM16A to myocytes suggests that this channel could play a major functional role. NEW & NOTEWORTHY In this study, we report the first observations of Cl− being a critical ionic component of spontaneous and agonist-evoked contractility in human lymphatics. The most consistently expressed Ca2+-activated Cl− channel gene in the human thoracic duct and mesenteric lymphatic vessels appears to be transmembrane member 16A, suggesting that this channel plays a major role.