The efficacy of cooling with phase change material for the treatment of exercise-induced muscle damage: pilot study

Post-exercise cryotherapy treatments are typically short duration interventions. This study examined the efficacy of prolonged cooling using phase change material (PCM) on strength loss and pain after eccentric exercise. Eight adults performed 120 bilateral eccentric quadriceps contractions (90% MVC). Immediately afterwards, frozen PCM packs (15°C) were placed over the quadriceps, with room temperature PCM packs on the contralateral quadriceps. Skin temperature was recorded continually (6 h PCM application). Isometric quadriceps strength and soreness were assessed before, 24, 48, 72 and 96 h post-exercise. The protocol was repeated 5 months later, with room temperature PCM applied to both legs. There were three treatments: legs treated with 15°C PCM packs (direct cooling), legs treated with room temperature PCM packs contralateral to the 15°C PCM packs (systemic cooling), and legs tested 5 months later both treated with room temperature PCM packs (control). Skin temperature was 9°C-10°C lower with direct cooling versus systemic cooling and control (P < 0.01). Strength loss and soreness were less (P < 0.05) with direct cooling versus systemic cooling and control (strength 101%, 94%, 93%, respectively; pain 1.0, 2.3, 2.7, respectively). Six hours of PCM cooling was well tolerated and reduced strength loss and pain after damaging exercise.

A2 Milk Enhances Dynamic Muscle Function Following Repeated Sprint Exercise, a Possible Ergogenic Aid for A1-Protein Intolerant Athletes?

Hyperaminoacidemia following ingestion of cows-milk may stimulate muscle anabolism and attenuate exercise-induced muscle damage (EIMD). However, as dairy-intolerant athletes do not obtain the reported benefits from milk-based products, A2 milk may offer a suitable alternative as it lacks the A1-protein. This study aimed to determine the effect of A2 milk on recovery from a sports-specific muscle damage model. Twenty-one male team sport players were allocated to three independent groups: A2 milk (n = 7), regular milk (n = 7), and placebo (PLA) (n = 7). Immediately following muscle-damaging exercise, participants consumed either A2 milk, regular milk or PLA (500 mL each). Visual analogue scale (muscle soreness), maximal voluntary isometric contraction (MVIC), countermovement jump (CMJ) and 20-m sprint were measured prior to and 24, 48, and 72 h post EIMD. At 48 h post-EIMD, CMJ and 20-m sprint recovered quicker in A2 (33.4 ± 6.6 and 3.3 ± 0.1, respectively) and regular milk (33.1 ± 7.1 and 3.3 ± 0.3, respectively) vs. PLA (29.2 ± 3.6 and 3.6 ± 0.3, respectively) (p < 0.05). Relative to baseline, decrements in 48 h CMJ and 20-m sprint were minimised in A2 (by 7.2 and 5.1%, respectively) and regular milk (by 6.3 and 5.2%, respectively) vs. PLA. There was a trend for milk treatments to attenuate decrements in MVIC, however statistical significance was not reached (p = 0.069). Milk treatments had no apparent effect on muscle soreness (p = 0.152). Following muscle-damaging exercise, ingestion of 500 mL of A2 or regular milk can limit decrements in dynamic muscle function in male athletes, thus hastening recovery and improving subsequent performance. The findings propose A2 milk as an ergogenic aid following EIMD, and may offer an alternative to athletes intolerant to the A1 protein.

Minimal muscle damage after a marathon and no influence of beetroot juice on inflammation and recovery

This study examined whether beetroot juice (BTJ) would attenuate inflammation and muscle damage following a marathon. Using a double blind, independent group design, 34 runners (each having completed ca. ∼16 previous marathons) consumed either BTJ or an isocaloric placebo (PLA) for 3 days following a marathon. Maximal isometric voluntary contractions (MIVC), countermovement jumps (CMJ), muscle soreness, serum cytokines, leucocytosis, creatine kinase (CK), high sensitivity C-reactive protein (hs-CRP), and aspartate aminotransferase (AST) were measured pre, post, and 2 days after the marathon. CMJ and MIVC were reduced after the marathon (P < 0.05), but no group differences were observed (P > 0.05). Muscle soreness was increased in the day after the marathon (BTJ; 45 ± 48 vs. PLA; 46 ± 39 mm) and had returned to baseline by day 2, irrespective of supplementation (P = 0.694). Cytokines (interleukin-6; IL-6, interleukin-8, tumour necrosis factor-α) were increased immediately post-marathon but apart from IL-6 had returned to baseline values by day 1 post. No interaction effects were evident for IL-6 (P = 0.213). Leucocytes increased 1.7-fold after the race and remained elevated 2 days post, irrespective of supplement (P < 0.0001). CK peaked at 1 day post marathon (BTJ: 965 ± 967, and PLA: 1141 ± 979 IU·L^-1) and like AST and hs-CRP, was still elevated 2 days after the marathon (P < 0.05); however, no group differences were present for these variables. Beetroot juice did not attenuate inflammation or reduce muscle damage following a marathon, possibly because most of these indices were not markedly different from baseline values in the days after the marathon.

Postexercise cold-water immersion improves intermittent high-intensity exercise performance in normothermia

A brief cold water immersion between 2 continuous high-intensity exercise bouts improves the performance of the latter compared with passive recovery in the heat. We investigated if this effect is apparent in normothermic conditions (∼19 °C), employing an intermittent high-intensity exercise designed to reflect the work performed at the high-intensity domain in team sports. Fifteen young active men completed 2 exhaustive cycling protocols (Ex1 and Ex2: 12 min at 85% ventilatory threshold (VT) and then an intermittent exercise alternating 30-s at 40% peak power (P_peak) and 30 s at 90% P_peak to exhaustion) separated by 15 min of (i) passive rest, (ii) 5-min cold-water immersion at 8 °C, and (iii) 10-min cold-water immersion at 8 °C. Core temperature, heart rate, rates of perceived exertion, and oxygen uptake kinetics were not different during Ex1 among conditions. Time to failure during the intermittent exercise was significantly (P < 0.05) longer during Ex2 following the 5- and 10-min cold-water immersions (7.2 ± 3.5 min and 7.3 ± 3.3 min, respectively) compared with passive rest (5.8 ± 3.1 min). Core temperature, heart rate, and rates of perceived exertion were significantly (P < 0.05) lower during most periods of Ex2 after both cold-water immersions compared with passive rest. The time constant of phase II oxygen uptake response during the 85% VT bout of Ex2 was not different among the 3 conditions. A postexercise, 5- to 10-min cold-water immersion increases subsequent intermittent high-intensity exercise compared with passive rest in normothermia due, at least in part, to reductions in core temperature, circulatory strain, and effort perception.

Effects of Beetroot Juice on Recovery of Muscle Function and Performance between Bouts of Repeated Sprint Exercise

This study examined the effects of beetroot juice (BTJ) on recovery between two repeated-sprint tests. In an independent groups design, 20 male, team-sports players were randomized to receive either BTJ or a placebo (PLA) (2 × 250 mL) for 3 days after an initial repeated sprint test (20 × 30 m; RST1) and after a second repeated sprint test (RST2), performed 72 h later. Maximal isometric voluntary contractions (MIVC), countermovement jumps (CMJ), reactive strength index (RI), pressure-pain threshold (PPT), creatine kinase (CK), C-reactive protein (hs-CRP), protein carbonyls (PC), lipid hydroperoxides (LOOH) and the ascorbyl free radical (A^•−) were measured before, after, and at set times between RST1 and RST2. CMJ and RI recovered quicker in BTJ compared to PLA after RST1: at 72 h post, CMJ and RI were 7.6% and 13.8% higher in BTJ vs. PLA, respectively (p < 0.05). PPT was 10.4% higher in BTJ compared to PLA 24 h post RST2 (p = 0.012) but similar at other time points. No group differences were detected for mean and fastest sprint time or fatigue index. MIVC, or the biochemical markers measured (p > 0.05). BTJ reduced the decrement in CMJ and RI following and RST but had no effect on sprint performance or oxidative stress.

Ibuprofen Ingestion Does Not Affect Markers of Post-exercise Muscle Inflammation

Purpose: We investigated if oral ingestion of ibuprofen influenced leucocyte recruitment and infiltration following an acute bout of traditional resistance exercise

Methods: Sixteen male subjects were divided into two groups that received the maximum over-the-counter dose of ibuprofen (1200mg d⁻¹) or a similarly administered placebo following lower body resistance exercise. Muscle biopsies were taken from m.vastus lateralis and blood serum samples were obtained before and immediately after exercise, and at 3 and 24 h after exercise. Muscle cross-sections were stained with antibodies against neutrophils (CD66b and MPO) and macrophages (CD68). Muscle damage was assessed via creatine kinase and myoglobin in blood serum samples, and muscle soreness was rated on a ten-point pain scale.

Results: The resistance exercise protocol stimulated a significant increase in the number of CD66b⁺ and MPO⁺ cells when measured 3 h post exercise. Serum creatine kinase, myoglobin and subjective muscle soreness all increased post-exercise. Muscle leucocyte infiltration, creatine kinase, myoglobin and subjective muscle soreness were unaffected by ibuprofen treatment when compared to placebo. There was also no association between increases in inflammatory leucocytes and any other marker of cellular muscle damage.

Conclusion: Ibuprofen administration had no effect on the accumulation of neutrophils, markers of muscle damage or muscle soreness during the first 24 h of post-exercise muscle recovery.

Regular postexercise cooling enhances mitochondrial biogenesis through AMPK and p38 MAPK in human skeletal muscle

This study investigated the effect of regular postexercise cold water immersion (CWI) on muscle aerobic adaptations to endurance training. Eight males performed 3 sessions/wk of endurance training for 4 wk. Following each session, subjects immersed one leg in a cold water bath (10°C; COLD) for 15 min, while the contralateral leg served as a control (CON). Muscle biopsies were obtained from vastus lateralis of both CON and COLD legs prior to training and 48 h following the last training session. Samples were analyzed for signaling kinases: p38 MAPK and AMPK, peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), enzyme activities indicative of mitochondrial biogenesis, and protein subunits representative of respiratory chain complexes I-V. Following training, subjects' peak oxygen uptake and running velocity were improved by 5.9% and 6.2%, respectively (P < 0.05). Repeated CWI resulted in higher total AMPK, phosphorylated AMPK, phosphorylated acetyl-CoA carboxylase, β-3-hydroxyacyl-CoA-dehydrogenase and the protein subunits representative of complex I and III (P < 0.05). Moreover, large effect sizes (Cohen's d > 0.8) were noted with changes in protein content of p38 (d = 1.02, P = 0.064), PGC-1α (d = 0.99, P = 0.079), and peroxisome proliferator-activated receptor α (d = 0.93, P = 0.10) in COLD compared with CON. No differences between conditions were observed in the representative protein subunits of respiratory complexes II, IV, and V and in the activities of several mitochondrial enzymes (P > 0.05). These findings indicate that regular CWI enhances p38, AMPK, and possibly mitochondrial biogenesis.

Confounding compression: the effects of posture, sizing and garment type on measured interface pressure in sports compression clothing

The purpose of this investigation was to measure the interface pressure exerted by lower body sports compression garments, in order to assess the effect of garment type, size and posture in athletes. Twelve national-level boxers were fitted with sports compression garments (tights and leggings), each in three different sizes (undersized, recommended size and oversized). Interface pressure was assessed across six landmarks on the lower limb (ranging from medial malleolus to upper thigh) as athletes assumed sitting, standing and supine postures. Sports compression leggings exerted a significantly higher mean pressure than sports compression tights (P < 0.001). Oversized tights applied significantly less pressure than manufacturer-recommended size or undersized tights (P < 0.001), yet no significant differences were apparent between different-sized leggings. Standing posture resulted in significantly higher mean pressure application than a seated posture for both tights and leggings (P < 0.001 and P = 0.002, respectively). Pressure was different across landmarks, with analyses revealing a pressure profile that was neither strictly graduated nor progressive in nature. The pressure applied by sports compression garments is significantly affected by garment type, size and posture assumed by the wearer.

Caffeine delays autonomic recovery following acute exercise

BACKGROUND

Impaired autonomic recovery of heart rate (HR) following exercise is associated with an increased risk of sudden death. Caffeine, a potent stimulator of catecholamine release, has been shown to augment blood pressure (BP) and sympathetic nerve activity; however, whether caffeine alters autonomic function after a bout of exercise bout remains unclear.

METHODS

In a randomized, crossover study, 18 healthy individuals (26 ± 1 years; 23.9 ± 0.8 kg·m(-2)) ingested caffeine (400 mg) or placebo pills, followed by a maximal treadmill test to exhaustion. Autonomic function and ventricular depolarization/repolarization were determined using heart rate variability (HRV) and corrected QT interval (QTc), respectively, at baseline, 5, 15, and 30 minutes post-exercise.

RESULTS

Maximal HR (HRmax) was greater with caffeine (192 ± 2 vs. 190 ± 2 beat·min(-1), p < 0.05). During recovery, HR, mean arterial pressure (MAP), and diastolic blood pressure (DBP) remained elevated with caffeine (p < 0.05). Natural log transformation of low-to-high frequency ratio (LnLF/LnHF) of HRV was increased compared with baseline at all time points in both trials (p < 0.05), with less of an increase during 5 and 15 minutes post-exercise in the caffeine trial (p < 0.05). QTc increased from baseline at all time points in both trials, with greater increases in the caffeine trial (p < 0.05).

CONCLUSIONS

Caffeine ingestion disrupts post-exercise autonomic recovery because of increased sympathetic nerve activity. The prolonged sympathetic recovery time could subsequently hinder baroreflex function during recovery and disrupt the stability of autonomic function, potentiating a pro-arrhythmogenic state in young adults.

Overshoot phenomenon of oxygen uptake during recovery from maximal exercise in patients with previous myocardial infarction

The overshoot in oxygen uptake (VO2 overshoot) during recovery from maximal exercise is thought to reflect an overshoot in cardiac output. We investigated whether this phenomenon is related to cardiopulmonary function during exercise in cardiac patients. A total of 201 consecutive patients with previous myocardial infarction underwent cardiopulmonary exercise testing (CPX). An apparent VO2 overshoot during the recovery from CPX (6.5+/-8.1% increase relative to the peak VO2) was observed in ten patients. A comparison of patients with the VO2 overshoot to those without the VO2 overshoot revealed that the former had a significantly lower left ventricular ejection fraction (40.1+/-19.1 vs. 55. 2+/-14.9%, respectively, p = 0.002) and larger left ventricular diastolic and systolic dimensions. Patients with the VO2 overshoot also had a significantly lower peak VO2 (13.1+/-6.1 vs. 18.1+/-4.5 ml/min/kg, p < 0.001), lower DeltaVO2/DeltaWR (work rate) (6.6+/-3.8 vs. 9.5+/-1.7 mL/min/W, p < 0.0001), and a higher E (minute ventilation)/VCO2 (carbon dioxide output) slope (45.0+/-18.6 vs. 32.6+/-6.6, p < 0.0001) than those without the overshoot. A VO2 overshoot during recovery from maximal exercise was found in 5% of patients with previous myocardial infarction. This condition, which suggests a transient mismatch between cardiac contractility and afterload reduction, was found to be related to impaired cardiopulmonary function during exercise.