In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: ALF injection resulted in a marked increase in hindlimb EMG activity in the L - MED treatment group which was indistinguishable from that seen in animals treated with saline .
### Output Text:
<span class="chemical">ALF</span> injection resulted in a marked increase in hindlimb EMG activity in the L - MED treatment group which was indistinguishable from that seen in animals treated with saline . 