Box2d Player constantly jumping when using enum - c++

Question

I am trying to create a player that jumps and moves left and right.
At the moment, the player jumps infinitely on the spot, or moves infinitely left or right when the corresponding keys are pressed.
What do I need to add to this code to make the character stop jumping or moving once the key is released?
Here is the code so far:
void Character::update()
{
b2Vec2 pos = m_body->GetPosition();
setPosition(pos.x, pos.y);
float angle = m_body->GetAngle()* RAD2DEG;
setRotation(angle);
if (m_movingStates[LEFT])
{
m_body->ApplyLinearImpulseToCenter(b2Vec2(-0.03, 0.0f), true);
}
if (m_movingStates[RIGHT])
{
m_body->ApplyLinearImpulseToCenter(b2Vec2(0.03, 0.0f), true);
}
if (m_movingStates[JUMP] && m_sit)
{
m_body->ApplyLinearImpulseToCenter(b2Vec2(0.f, -0.1f), true);
}
}
void Character::onKeyPress(sf::Event event)
{
if (event.key.code == sf::Keyboard::Left)m_movingStates[LEFT] = true;
if (event.key.code == sf::Keyboard::Right)m_movingStates[RIGHT] = true;
if (event.key.code == sf::Keyboard::Space)m_movingStates[JUMP] = true;
}
void Character::onKeyRelease(sf::Event event)
{
if (event.type == sf::Event::KeyReleased && event.key.code == sf::Keyboard::Left) m_movingStates[LEFT] = false;
if (event.type == sf::Event::KeyReleased && event.key.code == sf::Keyboard::Right) m_movingStates[RIGHT] = false;
if (event.type == sf::Event::KeyReleased && event.key.code == sf::Keyboard::Space) m_movingStates[JUMP] = false;
}