The production effect: the role of attentional resources

The production effect is the benefit in memory found for produced (i.e., read aloud) words relative to words read silently. It is proposed that the production effect occurs as a result of the enhanced distinctiveness associated with the produced items. The current research investigated whether attentional resources are required to encode and/or retrieve the distinctive information associated with the produced words. The literature suggests that the encoding of this distinctive information occurs automatically, but at test, purposeful attention is required to retrieve this distinctive information. To test this, participants read words aloud and silently, under either full or divided attention. Participants then completed either a recognition (Experiment 1) or free recall (Experiment 2) memory test under either full or divided attention. The findings show that when attention is divided at encoding, the benefit for aloud words remains for both recognition and free recall. When attention is divided at test, however, the benefit for aloud words remains for recognition but is absent for free recall. Overall, these results suggest that the distinctive information associated with produced words is encoded automatically, but it may not be accessible at test under attentionally demanding conditions.

The dual effect of normobaric hypoxia on heart rate variability and substrate partitioning following interval cycling

Recent studies have shown the importance of the beat-by-beat changes in heart rate influenced by the autonomic nervous system (ANS), or heart rate variability (HRV). The purpose of this study was to examine the lasting effects of hypoxic exercise on HRV, and its influences on substrate usage. Results from this study could lead an increased understanding on this topic. Eight active healthy males (age: 31±11 years; height: 180±7 cm; weight: 83±8 kg; VO₂max (maximal oxygen consumption): 4.4±0.6 L•min⁻¹) underwent normoxic and hypoxic (FᵢO₂= 0.15) conditions during high-intensity interval (HIIT) cycling (70%-high interval, 35%-rest interval). Cycling intensity was determined by a peak power output cycling test. Each experimental session consisted of a basal metabolic rate determination, up to 45-minutes of HIIT cycling, and three 30-minute post-exercise metabolic rate measurements (spanning 3 hours and 15 minutes after exercise). During exercise, RPE was higher (p<0.01) and LAC (lactate) increased (p=0.001) at each point of time in hypoxia, with no change in normoxia. After hypoxic exercise, the SNS/PNS ratio (overall ANS activity) was significantly higher (p<0.01) and significantly decreased through time in both conditions (p<0.01). In addition, a significant interaction between time and conditions (p<0.02) showed a decrease in LAC concentration through time post-hypoxic exercise. The findings showed that a single bout of hypoxic exercise alters ANS activity post-exercise along with shifting substrate partitioning from glycolytic to lipolytic energy production. The significant decrease in LAC concentration post-hypoxic exercise supports the notion that hypoxic HIIT induces a greater muscle glycogen depletion leading to increased fat oxidation to sustain glycogenesis and gluconeogenesis to maintain blood glucose level during recovery.