Heat acclimation (HA) increases tolerance to exercise performed in the heat and may improve maximal oxygen uptake (V O 2 max) in temperate environments. However, it is unknown if HA affects the expression of proteins related to mitochondrial biogenesis and oxidative capacity in skeletal muscle. The purpose of this study was to investigate the effect of HA on skeletal muscle markers of mitochondrial biogenesis and oxidative phosphorylation in recreationally trained adults. Thirteen (7 males and 6 females) individuals underwent 10 days of HA. Participants performed two 45 min bouts of exercise (walking at 30-40% maximal velocity at 3% grade) with 10 min rest per session in a hot environment (∼42 • C and 30-50% relative humidity). V O 2 max , ventilatory thresholds (VT), and protein expression of peroxisome proliferatoractivated receptor γ coactivator 1α (PGC-1α), mitochondrial transcription factor A (TFAM), calcium/calmodulin-dependent protein kinase (CaMK), electron transport chain (ETC) complexes I-IV, and heat shock protein 72 (Hsp72) in skeletal muscle were measured pre-and post-HA. Comparing day 1 to day 10, HA was confirmed by lower resting core temperature (T core) (P = 0.026), final T core (P < 0.0001), mean heart rate (HR) (P = 0.002), final HR (P = 0.003), mean ratings of perceived exertion (RPE) (P = 0.026) and final RPE (P = 0.028). Pre-to post-HAV O 2 max (P = 0.045) increased but VT1 (P = 0.263) and VT2 (P = 0.239) were unchanged. Hsp72 (P = 0.007) increased, but skeletal muscle protein expression (PGC-1α, P = 0.119; TFAM, P = 0.763; CaMK,

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2022-Reciprocal supersets (RSSs) are a time-efficient style of resistance exercise (RE) that consist of performing 2 consecutive exercises with opposing muscle groups while limiting rest times between them. Previous research in men indicates a RSS has an increased physiological response when compared with traditional RE (TRAD). No between-sex comparison of metabolic data for RSSs exists. The purpose of this study was to create a metabolic profile for RSSs in men and women. Eighteen resistance-trained individuals underwent 2 bouts of volume-load equated RE: RSS and TRAD. Reciprocal superset exercises were split into 3 clusters: (a) hexagonal bar deadlift superset with leg press, (b) chest press superset with seated row, and (c) overhead dumbbell press superset with latissimus dorsi pull-downs. The TRAD protocol, doing the same exercises, emulated hypertrophy emphasis training. Oxygen uptake (V Ȯ2 ), heart rate (HR), blood lactate ([BLa]), rate of perceived exertion (RPE), and excess post-exercise oxygen consumption (EPOC) were measured. Aerobic and anaerobic energy expenditure were estimated using V Ȯ2 and lactate, respectively. The level of significance set for this study was p # 0.05. Regardless of sex, a RSS elicited significantly greater average V Ȯ2 , HR, [BLa], RPE, and anaerobic and aerobic energy expenditures, and was completed in a shorter time compared with TRAD (p # 0.05). When compared with women, men had significantly greater EPOC, average [BLa], and anaerobic and aerobic energy expenditures during RSSs (p # 0.05). The average [BLa] and aerobic energy expenditure of the men were also significantly greater than the women during TRAD (p # 0.05). This study suggests that a RSS is a metabolically demanding RE session that may elicit increases in musculoskeletal, cardiorespiratory, and physiological adaptations while decreasing the duration of exercise.

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