The 28-year-old Tintu, mentored by Usha, has enjoyed success at the Continental level, winning a bronze and a silver at the Asian Games - 2010 Guangzhou (2:01.36) and 2014 Incheon (1:59.19) apart from six medals at the Asian Championships.
However at the World Championships, where the best in the business compete, she has struggled to make an impression in her three attempts so far.
She finished 15th in Daegu (South Korea, 2011) only to be eliminated in the 800m semi-finals and 19th in Beijing (2015), where she could not proceed beyond the Heats.
Usha, who is country's greatest ever female sprinter till date, has been training her from the beginning. The 'Payyoli Express' says she won't take criticism for Tintu's average success at the global meets and strongly objected to the suggestions that a foreign coach can help her ward improve.
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"For me it's not a problem but show me one foreign coach who has come here, trained Indian athletes and has got the medals (World Championship and Olympics)," Usha counter- questioned.
"It is up to Tintu, not me (to decide on her future). Tintu is senior Asiad medallist, Jessy Joseph is junior Asian Championship gold medallist, Jisna Matthew (Indian relay team member) is also there. Lot of others are coming up," she said, defending her training methods.
Usha, who missed an Olympic bronze by 0.01 seconds at 1984 Los Angeles Games, also explained how she has been trying different strategies to help Tintu improve.
"The other one is run a slow lap and maybe the same second lap. The second one may be 1 second lower than the first. But this is a very rare case in the world, it is a very rare case. It is not possible for everybody. Tintu was trying both the but it was not suiting," Usha explained.
"Whether you are running in the front or at the back the time will be there. She tried 60 seconds (for first lap) in China (during the Asian Grand Prix). If she goes for 60-61 seconds, it is not possible for Tintu to pick up (for concluding part of race).
"If she goes for 60 seconds in the first lap, upto 600m she will get slower and timing will go upto 1 min 30 seconds. If she goes upto 1 minute 31 secodns, it will go above 2 minute 03 second, no doubt. If she runs sub 1:30 min (till 600m), she will then come under 2:02 min undoubtedly and if she is under 1:20, she will clock a sub-two minute timing," she further explained the issue.
"She is not comfortable when she goes slow. If you run 1:30 for 600m, the (last) 200m will be same, if you are 1:27.5 then also the (last) 200m will be same. If she goes slow and try for acceleration, her muscles get stiff, not giving her the pull (required during finishing stage)."
Usha defended Tintu's 29th place finish at the Rio Olympics citing her health condition.
"Last Olympics, she had bronchial infection and 800m runners need more oxygen. It was difficult for her but she did it in two minutes, which is a world class time. So, if she goes fast, she will be capable of performing better."
She informed that Tintu has slowly started preparing for London as she was down with fever after coming back from China.
"Her endurance is ok. For speed, she needs 20-25 days to get back to normal. We have started slowly but it would require more effort."
Usha said competition exposure was must for Indian athletes to improve.
"Last year Tintu was in a very good form but she got only one competition outside. When you compete with better athletes, you also get better. When you go out it's for learning, win or defeat doesn't matter. In athletics it is not happening," she concluded.