Possible Association of Energy Availability with Transferrin Saturation and Serum Iron during Summer Camp in Male Collegiate Rugby Players

Low energy availability (LEA) may persist in rugby players. However, timely assessment of energy balance is important but is difficult. Therefore, a practical index that reflects energy availability (EA) is essential. A total of 19 male college rugby players participated in a 2-week pre-season summer camp. Their blood sample was collected after overnight fast prior to (Pre), in the middle (Middle), and after (Post) the camp. Their physical activity in the first half of the camp was calculated using the additive factor method in the forwards (FW; numbers 1–8) and backs (BK; numbers 9–15). The participants were categorized as tight five (T5; numbers 1–5), back row (BR; numbers 6–8), and BK for analysis. All the participants lost weight during the camp (range: from −5.9% to −0.1%). Energy balance in the first half of the camp was negative. Transferrin saturation (TSAT) and serum iron levels significantly decreased to half, or even less, compared with the Pre levels at week 1 and remained low. The changes in TSAT and serum iron levels exhibited a significant positive correlation with the changes in body weight (R = 0.720; R = 0.627) and with energy intake (R = 0.410; R = 461) in T5. LEA occurs in rugby summer camp but is difficult to assess using weight change. Alternately, TSAT and serum iron levels after overnight fast may be better predictors of LEA.

Stimulus-Response Incompatibility: Extra Processing Stages versus Response Competition

The extra processing time required by incompatible S-R arrays has been explained in two ways: an increased number of processing stages or response competition from the compatible response. The additive factor method was employed, combining an S-R compatibility factor with a known response competition factor (a spatial Stroop task). The relationship between these two factors was shown to be an additive one, indicating that the two variables have their loci in (at least) two separate stages. This outcome is seen as persuasive evidence that longer reaction times for incompatible responses result from extra processing stages, rather than from response competition.