Heart rate and metabolic response to competitive squash in veteran players: identification of risk factors for sudden cardiac death

Abstract

We studied 10 older males during a competitive game and the early post-exercise period to define the metabolic response to squash in veteran players. For comparison, all subjects were also studied during exhaustive treadmill exercise. Squash caused a dramatic increase in heart rate (150%), and circulating levels of noradrenaline (164%), adrenaline (93%), lactate (202%) and free fatty acids (67%). These effects were independent of haemoconcentration. The early post-exercise period (5 min) was characterized by persistent elevation of plasma catecholamines, lactate, and free fatty acids, hypokalaemia and ventricular arrhythmias. The heart rate and metabolic responses to squash were similar in pattern and magnitude to those observed during treadmill exercise, highlighting the strenuous nature of squash as a recreation sport. While these changes may represent appropriate physiological adaptation to exercise in health, each has been implicated in the pathogenesis of fatal ventricular arrhythmias in subjects with ischaemic heart disease. These data support the contention that squash may be an inappropriate form of exercise for older men with coronary artery disease.

Fluid Replacements after Squash: An Analysis of the Effects of Several Fluid Regimens on Exercise-Related Metabolic Changes

“…The glu cose-containing solutions had significant ef fects only on blood glucose levels following squash, causing significant elevations at 15 and 30 min following the game. The increases in lactate, free fatty acids and glucose with concomitant hypokalaemia in the postexer cise period, previously demonstrated by Bra dy et al [2], have been confirmed in this study. We have also demonstrated that de spite these metabolic changes, indicators of dehydration such as plasma osmolality and plasma sodium are not elevated in the early postexercise period, and that these subse quently fall to values below baseline up to 1 h after the game.…”

“…The observed changes have been postu lated to contribute to arrhythmias and sudden death in older men playing squash [2,3], Hypokalaemia can trigger arrhythmias in nor mal and ischaemic myocardium [6,7]. Free fatty acids have been implicated in the patho genesis of myocardial ischaemia and ventric ular arrhythmias in patients with coronary artery stenosis [8.…”

“…Northcote et al [1] have reported the acute changes in myocardial oxygen con sumption and metabolism which accompany intensive exercise. Consequently, Brady et al [2] have described dramatic changes in heart rate and metabolism in middle-aged players during and after squash. They found increases in circulating levels of noradrenaline (164%), adrenaline (93%), lactate (202%), free fatty acids (67%) and glucose (58%) at the end of the game, and in the early postexercise period there was an acute drop in potassium levels, with persistent elevation of lactate and free fatty acids.…”

“…They found increases in circulating levels of noradrenaline (164%), adrenaline (93%), lactate (202%), free fatty acids (67%) and glucose (58%) at the end of the game, and in the early postexercise period there was an acute drop in potassium levels, with persistent elevation of lactate and free fatty acids. While these changes represent ap propriate physiological responses to exercise, they may contribute to the genesis of lethal arrhythmias in those with underlying isch aemia [2,3].…”

“…Previous studies concerning fluid replace ments have dealt with endurance sports and may not be applicable to squash [4,5], One potentially important benefit would be to ameliorate the circulating metabolic changes after squash, such as the fall in potassium lev els, as 23% of sudden deaths are in the early postexercise period [1]. However, the fall in potassium levels after squash returns to base line within 30 min of the end of the match [2], Thus, sufficient quantities of potassium would have to be rapidly absorbed into the circulation to affect the postexercise hypokalaemia. Also, the quantities of potassium in drinks are limited by palatability.…”