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Q: Physiologically, what is responsible for the phenomenon known as the “second wind”? Is it related to an individual’s fitness level?

A: No matter how fit individuals are, the first few minutes into vigorous exercise may cause their muscles to ache and make them somewhat out of breath. The body isn’t able to transport oxygen to the active muscles quickly enough. As a result, the muscles burn carbohydrates anaerobically, causing an increase in lactic acid production. Gradually, the body makes the transition to aerobic metabolism, and begins to burn nutrients (carbohydrates and fats) aerobically. This shift to aerobic metabolism coincides with the “second wind.” The more people train and the more fit they become, the sooner they will get their “breath” back. Then they will reach aerobic levels they can sustain for extended durations.

‘Foot’notes on Climbing

Q: I’ve had several clients report that they experience a mild numbness and tingling in their feet after working out on a stair climbing machine. Is this something they should be concerned about? Is there anything they can do to alter their stair climbing workouts to avoid experiencing the numbness and tingling?

A: In 1992, researchers at Stanford University surveyed frequent users of the StairMaster 4000 PT stair climber at seven health clubs to determine if neurologic foot symptoms were present during their exercise bouts. Of the 212 individuals who responded to their questionnaires, 39 percent reported that they had experienced numbness or tingling in their feet while using the stair climber. These mild-to-moderate forefoot neurologic symptoms generally disappeared either as the individuals continued to exercise or when the exercise session ended.

These researchers concluded that the exercisers’ symptoms (a condition collectively referred to as transient paresthesia) were probably caused by the compression of the interdigital nerves from persistent and prolonged weight bearing while exercising.

According to the investigators, these forefoot symptoms are most appropriately characterized as neurology nuisances, and not pathologic neuropathies. Fortunately, such neurologic nuisances don’t require formal medical treatment. Individuals may be able to alleviate or greatly minimize the symptoms by slightly altering their workout technique in one or more ways, including:

* Avoiding repetitive metatarsophalangeal dorsiflexion (i.e., bending-flexing the toes toward the body) by maintaining a flat-footed position on the foot pedals.

* Wearing proper footwear that provides ample width at the toe box and wearing shock-absorbing inserts.

* Loosening shoelaces if numbness or tingling develops.

* Limiting the duration of stair climbing machine workouts to less than 30 minutes.