Question: Who coached the "queen of Indian track and field"?

Context paragraphs:
Mayookha Johny: Mayookha Johny (born 9 April 1988) is an Indian track and field athlete from Kerala who specialises in long jump and triple jump.  She holds the current Indian National record for triple jump with a mark of 14.11 m (46 ft floor(((14.11)*3.28084)−(floor((14.11)*3.28084)) *12) in) .  She is the first Indian woman to cross the fourteen-metre mark.

Mercy Kuttan: Mercy Kuttan (born 1 January 1960) is a former Indian track and field athlete.  She was the first Indian woman longjumper to cross six meters.  In 1989, Mercy received Arjuna Award for her contribution to the Indian athletics.

PU Chitra: Chithra PU (born 9 June 1995 at Mundur, Palakkad District, Kerala) is an Indian track and field athlete from the state of Kerala.  She has won many state, national and international school meet gold medals in middle and long distance track events.

O. M. Nambiar: O. M. Nambiar (born 1932) is an Indian athletics coach who was awarded Dronacharya award in 1985.  He coached the well known Indian athlete P. T. Usha.  He hails from Kerala state.

Rakesh Kumar Yadav: Rakesh Kr Yadav (born 2 October 1977) is an Indian track and field athlete from Uttar Pradesh who specializes in Hammer throw.  Kumar set the Indian National record of 70.16m in the discipline on 17 July 2003 during the Second National Athletic Circuit Meet in Bangalore.  He erased the 70.13 metre mark of Ishtiaq Ahamed set there in the year 2000.

Milkha Singh: Milkha Singh (born between 1929 and 1935), also known as The Flying Sikh, is a former Indian track and field sprinter who was introduced to the sport while serving in the Indian Army.  He was the only Indian athlete to win an individual athletics gold medal at a Commonwealth Games until Krishna Poonia won the discus gold medal at the 2010 Commonwealth Games.  He also won gold medals in the 1958 and 1962 Asian Games.  He represented India in the 1956 Summer Olympics in Melbourne, the 1960 Summer Olympics in Rome and the 1964 Summer Olympics in Tokyo.  He was awarded the Padma Shri, India's fourth-highest civilian honour, in recognition of his sporting achievements.

K. M. Binu: Kalayathumkuzhi Mathews Binu (born 20 December 1980) is an Indian track and field athlete from Kerala who specializes in 400 metres and 800 metres.  He holds the current 400 metres national record of 45.48 s set at the 2004 Athens Olympics on 20 August 2004.  He broke the 44-year-old Olympics mark (by an Indian) held by Milkha Singh who set an Indian National Record with a timing of 45.73 s at the 1960 Rome Olympics.  He and his elder sister K. M. Beenamol made history when they became the first Indian siblings to win medals in a major international competition.  They won medals at the Busan Asian Games (2002).  While Binu won the men's 800 metres silver, his sister won the gold medal in the women's event.  Binu received the Arjuna Award for the year 2006 for his achievements in the Indian athletics.

P. T. Usha: Pilavullakandi Thekkeparambil Usha (born 27 June 1964), popularly known as P. T. Usha, is a retired Indian track and field athlete.  She has been associated with Indian athletics since 1979.  She is often called the "queen of Indian track and field".  She is nicknamed as the Payyoli Express.  Currently she runs the Usha School of Athletics at Koyilandy in Kerala.

Santhi Soundarajan: Santhi Soundarajan (also spelled "Shanthi Soundararajan",Tamil: சாந்தி சௌந்திரராஜன் , born April 1981) is an Indian track and field athlete.  She is the winner of 12 international medals for India and around 50 medals for her home state of Tamil Nadu.  Shanthi Soundarajan is the first Tamil woman to win a medal at the Asian Games.  She competes in middle distance track events.  She was stripped of a silver medal won at the 2006 Asian Games after failing a sex verification test which disputed her eligibility to participate in the women's competition.

Anil Singh (athlete): Anil Kumar Singh (born 4 March, 1985) is an Indian track and field athlete from Haryana who specializes in javelin throw.  He is the first Indian athlete to breach the 80-metre barrier in a competition.  Anil Singh holds the current Indian National record of 80.72 metre set at the Asian All Stars athletics championships held in Bhopal on 18 September 2008.  He replaced Satbir Singh's decade-old record of 79.68 metres, registered in Kolkata in October 1998.

Supporting paragraphs: O. M. Nambiar P. T. Usha
Answer: O. M. Nambiar