The physiological strain index does not reliably identify individuals at risk of reaching a thermal tolerance limit

Purpose The physiological strain index (PSI) was developed to assess individuals' heat strain, yet evidence supporting its use to identify individuals at potential risk of reaching a thermal tolerance limit (TTL) is limited. The aim of this study was to assess whether PSI can identify individuals at risk of reaching a TTL. Methods Fifteen females and 21 males undertook a total of 136 trials, each consisting of two 40-60 minute periods of treadmill walking separated by ~ 15 minutes rest, wearing permeable or impermeable clothing, in a range of climatic conditions. Heart rate (HR), skin temperature (T sk), rectal temperature (T re), temperature sensation (TS) and thermal comfort (TC) were measured throughout. Various forms of the PSI-index were assessed including the original PSI, PSI fixed , adaptive-PSI (aPSI) and a version comprised of a measure of heat storage (PSI HS). Final physiological and PSI values and their rate of change (ROC) over a trial and in the last 10 minutes of a trial were compared between trials completed (C, 101 trials) and those terminated prematurely (TTL, 35 trials). Results Final PSI original , PSI fixed , aPSI, PSI HS did not differ between TTL and C (p > 0.05). However, differences between TTL and C occurred in final T sk , T re-T sk , TS, TC and ROC in PSI fixed , T re , T sk and HR (p < 0.05). Conclusion These results suggest the PSI, in the various forms, does not reliably identify individuals at imminent risk of reaching their TTL and its validity as a physiological safety index is therefore questionable. However, a physiological-perceptual strain index may provide a more valid measure

Silagem de resíduos da filetagem de tilápia do nilo (Oreochromis niloticus), com ácido fórmico - análise Bromatológica, físico-química e microbiológica Silage of tilapia (Oreochromis niloticus) filetage residues with formic acid Bromatological, phisico-chemical and microbiological analyses

O experimento avaliou o valor nutritivo da silagem ácida da filetagem da tilápia do Nilo (Oreochromis niloticus Linneaus, 1758), visando sua utilização em substituição à farinha de peixe na alimentação de organismo aquático. A silagem consistiu de resíduos da filetagem de tilápia (carcaça) e 3% de ácido fórmico, armazenada em temperatura ambiente (máxima média de 21,5ºC) e temperatura mínima média de 15ºC, por trinta dias, em baldes de polietileno com um orifício, por onde os gases saiam. O pH foi monitorado no 1º, 15º e 30º dia. Foram realizadas análises microbiológicas para contagem total de microrganismos e coliformes a 35ºC e 45ºC. O pH apresentou média de 3,95 ao final dos 30 dias. Nas análises microbiológicas observou-se a ausência de coliformes a 45ºC e, que a quantidade de microrganismos diminuiu gradativamente. Do ponto de vista microbiológico, a silagem ácida de resíduo da filetagem de tilápia mostrou-se como alimento alternativo viável para a alimentação animal.<br>The experiment was carried out for evaluate the nutritional value of the silage of Nile tilapia (Oreochromis niloticus Linneaus, 1758) filetage residues with formic acid as a replace of fish meal in aquatic organisms feeding as protein source. The silage consisted of tilapia filetage residues (carcass) and 3% formic acid, and it was stored in environmental temperature with a maximum average of 21,5º C and a minimum average of 15 º C, during thirty days, in polyethylene pails with an orifice for the exhaustion of gases. The pH was monitored on the 1st, 15th and 30th day. The microbiological analyses were made for the total count of microorganisms and coliforms at 35º C and 45º C. The average pH was 3.95 at the end of 30 days. The microbiological analyses showed absence of coliformes at 45º C and a gradual reduction in the quantity of microorganisms. From the microbiological standpoint, the acid silage of tilapia residues was shown to be an alternative viable diet for animal feeding