A survey conducted by the National Fitness Association revealed that individuals who participate in regular exercise reported feeling more energetic and accomplished in daily tasks. The results showed that 80% of the respondents associated physical activity with increased energy levels. However, the association was criticized by skeptics who argued that correlation does not imply causation, suggesting that more factors need to be considered.
To strengthen the argument that regular exercise leads to higher energy levels, which of the following options would provide the most support?