ECSS Paris 2023: OP-PN35
INTRODUCTION: Heat therapy can promote cardiovascular health by lowering cardiovascular disease risk and mortality, potentially by reducing inflammation and altering arterial stiffness. While most research on heat therapy has focused on continuous heat exposure, traditional sauna practice involves alternating between heating and cooling down in 2-3 cycles. This study compares two methods: 60 min of continuous heating (CH) and intermittent heating (IH) consisting of three 20-min sessions with breaks. METHODS: Healthy young adults (n=21, 25.4±3.3 yrs, body mass index (BMI) 22.0±2.0 kg•m-2) underwent two trials in randomised order: CH exposure (air temperature: 71.8°C, humidity 7.6%) and IH exposure (72.0°C, 6.7%), separated by 15-min breaks (21.9°C, 41.8%). Blood samples to determine IL-6, IL-10 and IL-1ra plasma concentration were collected pre-, post- and 1 h post-intervention; brachial pulse pressure, central pulse pressure, augmentation index (AIx), rectal and skin temperature, basic affect and thermal comfort were assessed throughout the intervention. RESULTS: Rectal temperature was higher after CH compared with IH (P≤0.01, CH: 38.2±0.3°C, IH: 37.6±0.2°C). Plasma IL-6, IL-10 and IL-1ra concentrations did not differ between conditions (main effects: P≥0.383, interaction effects: P ≥0.057). An increase of IL-6 (P<0.001; pre to post, CH: 0.9±0.8 to 1.5±0.8 pg·ml−1, IH: 1.0±1.0 to 1.5±1.3 pg·ml−1) and IL-1ra was observed (P=0.008; pre to post, CH: 48.8±10.7 to 52.4±11.8 pg·ml−1, IH: 50.7±12.6 to 53.6±15.3 pg·ml−1). Post heat exposure, brachial and central pulse pressures were higher in CH than in IH (P≤0.002). In both conditions, AIx increased following 20 min of heat exposure (P≤0.042) but was lower in CH than IH at 40 and 60 min of heat exposure (P≤0.009). Post heat exposure, the mean skin temperature for CH was lower than for IH (CH: 38.1±1.5°C, IH: 38.7±1.0°C, P<0.001), and thermal discomfort was more pronounced for CH than IH (CH: 2.0±1.3, IH: 1.0±1.1, P=0.003). CONCLUSION: Despite CH leading to a higher rectal temperature than IH, CH and IH similarly raised the inflammatory markers IL-6 and IL-1ra, whilst the AIx response was blunted in IH following an initial increase. Both the inflammatory response as well as the temporary increase in AIx, indicating increased arterial stiffness, are comparable to the acute exercise response. Importantly, regular exercise can reduce resting inflammatory marker concentrations and improve arterial function and reduce stiffness, lowering AIx over time. It may hence be speculated that these observed acute changes during heat exposure may have long-term benefits of heat therapy, similar to regular exercise. Finally, although IH resulted in a higher mean skin temperature, this protocol was rated as more comfortable. These findings imply that for the inflammatory variables, the overall duration of passive heating might be more critical than a pronounced elevation of core temperature, which should be considered when designing effective heat therapy protocols.
Read CV Yunuo SuECSS Paris 2023: OP-PN35
INTRODUCTION: Unilateral trainings benefits on contralateral muscles have long been established, yet evidence for heterologous muscle cross education remains scarce. This study explored the overflow effect from ipsilateral exercises via two methods: firstly, a maximal eccentric contraction (MaxEC1) on elbow flexors, followed by one (MaxEC2) on same-side knee extensors; secondly, MaxEC1 on knee extensors, then MaxEC2 on elbow flexors. The aim was to investigate cross-educations protective effects, potentially reducing muscle damage and boosting recovery across different muscle groups with sequential eccentric contractions. METHODS: The study recruited 32 healthy women aged 20–30, divided into four groups: non-dominant upper limb / lower limb (NU/NL), control / non-dominant lower limb (C/NL), non-dominant lower limb / upper limb (NL/NU), and control / non-dominant upper limb (C/NU), each with eight participants. NU/NL group undertook 30 MaxEC1 with non-dominant elbow flexors and 60 MaxEC2 with knee extensors. NL/NU reversed this, with 60 MaxEC1 on knee extensors and 30 MaxEC2 on elbow flexors. C/NU did 30 MaxEC1 on elbow flexors, while C/NL did 60 MaxEC1 on knee extensors. NU/NL and NL/NU conducted their MaxEC2 14 days after MaxEC1. Variables measured included plasma creatine kinase (CK), muscle soreness (DOMS), limb circumference (CIR), joint range of motion (ROM), maximal voluntary isometric contraction (MVC) torque, maximal isokinetic concentric strength (ISOK), acoustic radiation force impulse (ARFI), and joint release angle (JRA), assessed before MaxEC1, after MaxEC2, and daily for five days post-MaxEC2. RESULTS: NU/NL exhibited quicker recovery in CK, DOMS, ROM, JRA, MVC, ISOK, and ARFI metrics compared to C/NL. Similarly, NL/NU demonstrated faster recovery across all measured variables when compared to C/NU. Notably, significant differences were observed between NU/NL and C/NL in DOMS on Day 2 post-MaxEC2 (p < .05), in MVC on Days 0–2 post-MaxEC2 (p < .05), in ISOK on Days 0–2 post-MaxEC2 (p < .05), in JRA at angles of 45° and 60° on Day 3 post-MaxEC2 (p < .05), and in CK on Days 1 and 2 post-MaxEC2 (p < .05). Between NL/NU and C/NU, significant differences emerged in ROM on Days 3–5 post-MaxEC2 (p < .05), in ARFI on Days 0–2 post-MaxEC2 (p < .05), in MVC on Days 0, 1, and 4 post-MaxEC2 (p < .05), in ISOK across Days 0–5 post-MaxEC2 (p < .05), and in CK on Days 1 and 2 post-MaxEC2 (p < .05). CONCLUSION: The results of this study are similar to those found by Ben in 2018, which demonstrated that unilateral leg press resistance training can enhance both contralateral homologous and heterologous muscles (2). This study suggests that a maximal eccentric contraction on elbow flexors or knee extensors can reduce subsequent muscle damage in the same-side muscle group. These findings can aid coaches, trainers, and therapists in improving rehabilitation and training practices. Reference: 1. Hyldahl, et al., Exerc Sport Sci Rev., 2017 2. Ben Othman, et al., Appl Physiol Nutr Metab., 2018
Read CV Kuo-Wei TsengECSS Paris 2023: OP-PN35
INTRODUCTION: Whole-body or localised heating can increase the anabolic and strength responses to resistance exercise. However, it is unknown whether concurrent whole-body heating can improve performance or muscle mass adaptations during long-term resistance training. We therefore investigated the effects of whole-body heat stress applied concurrently during resistance training on muscle mass, strength, speed, agility, force and anabolic signalling in males. METHODS: Eighteen recreationally active males were assigned to HEAT (n = 8, age = 23.3 ± 3.1 years, body mass (BM) = 75.6 ± 14.5 kg, height = 175.6 ± 8.8 cm) or CON (n = 10, age = 21.0 ± 2.7 years, BM = 76.0 ± 11.3 kg, height = 177.2 ± 9.6 cm). Each group undertook 10 weeks of full body resistance training three days per week. CON trained at 23°C, relative humidity 25%, while HEAT trained at 40°C, relative humidity 30%. Strength (1RM leg and bench press), speed (5 and 10 m sprint), agility (T-test), peak force (during squat jump and ballistic push up) and body composition (DXA scan) were assessed at pre-, mid- (week five) and post-intervention. Vastus lateralis muscle biopsies were taken before, 1 h and 48 h after intensity-matched training sessions conducted pre- and post-intervention. Core body temperature and vastus lateralis muscle temperature were measured during the second training session via ingestible telemetric capsule and indwelling thermistor, respectively. RESULTS: Despite the much higher environmental training temperature for HEAT, peak core body temperature and peak muscle temperature were not significantly different between CON (38.0 ± 0.2°C; 36.0 ± 0.5°C) and HEAT (38.2 ± 0.1°C; 36.8 ± 0.6°C). Leg press 1 RM increased similarly in both CON (50.25 ± 13.99 kg, p<0.05) and HEAT (32.75 ± 5.89 kg, p<0.05) while bench press 1RM showed no improvement in either group. No improvements were observed in 5 m or 10 m sprint time, agility, or peak force generated during a squat jump or ballistic push up in either group. Total body lean mass and appendicular lean mass increased in CON only by 3.2% and 2.8%, respectively. Upper body lean mass increased and lower body lean mass was unchanged, with no differences between groups. Type I and Type II muscle fibre cross-sectional areas increased in CON only. Myonuclear density increased only in CON, whereas the increase in satellite cell content was not different between HEAT and CON. Markers of the mTOR signalling pathway (total and phospho- Akt, mTOR, p70S6k, 4E-BP1, rpS6) were largely similar between HEAT and CON. CONCLUSION: These results indicate that, despite no effects on core or muscle temperature, resistance training in a hot environment impaired muscle hypertrophy but had no effect on performance adaptations.
Read CV Aaron PetersenECSS Paris 2023: OP-PN35