We report the first results from a study of the internal kinematics , based on spatially resolved H _ { \alpha } velocity profiles , of three galaxies at redshift z \sim 0.6 and one at redshift z \sim 0.8 , detected by ISOCAM in the Hubble Deep Field South .
The kinematics are derived from high resolution near-infrared VLT spectroscopy .
One of the galaxies is a massive spiral which possesses a very large rotational velocity of 460 km s ^ { -1 } and contains a mass of 10 ^ { 12 } M _ { \odot } ( within 20 kpc ) , significantly higher than the dynamical masses measured in most other local and high redshift spirals .
Two of the galaxies comprise a counter-rotating interacting system , while the fourth is also a large spiral .
The observed galaxies are representative examples of the morphologies encountered among ISOCAM galaxies .
The mass-to-light ( M / L _ { bol } ) ratios of ISOCAM galaxies lie between those of local luminous IR galaxies and massive spirals .
We measure an offset of 1.6 \pm 0.3 mag in the rest frame B-band and of 0.7 \pm 0.3 mag in the rest frame I-band when we compare the four ISOCAM galaxies to the local Tully-Fisher B and I-band relations .
We conclude that the large IR luminosity of the ISOCAM population results from a combination of large mass and efficient triggering of star formation .
Since ISOCAM galaxies contribute significantly to the Cosmic Infrared Background our results imply that a relatively small number of very massive and IR luminous objects contribute significantly to the IR background and star formation activity near z \sim 0.7 .