|1952, Italian Fausto Coppi is drenched with water by a fan during the golden years of the Tour. Question: Can the topical application of K & Mg do the same magic? Answer: That's very unlikely, ...|
The authors' conclusion that "[a]fter administration of potassium-magnesium-aspartate [KMgA] the capacity for prolonged exercise increased about 50 per cent" (Ahlborg. 1968) can thus not be discarded as marketing babble. And, before we decide whether it's too good to be true, I'd suggest we take a closer look at the way the data was generated before we either (a) discard it as outdated or (b) get totally excited for nothing.
Another ten years before Ahlborg et al. published their study, an effect of potassium and magnesium salts of aspartic acid on muscular fatigability has been demonstrated experimentally in animals by several independent research groups. Back in the 1960s, humans studies had yet only subjectively assessed the effects of KMgA on endurance performance in man. Ahlborg et al. were thus right to consider it... "to be of interest to investigate, whether a positive effect on the capacity for prolonged standardized physical exercise after oral administration of potassium-magnesium-aspartate can be objectively demonstrated" (Ahlberg. 1968).
|Table 1: Some anthropometric and other data in the test subjects (Ahlborg. 1968).|
To get the results they wanted and to make sure the subjects' performance was not thwarted, the scientists required all subjects to record all foods they'd been consuming for the 4 days of the test. This practice was meant to avoid interference with of high carbohydrate intakes of which people back in the day still knew and appreciated that they can "increase the capacity for prolonged exercise markedly" (Ahlborg. 1968).
Does this work for strength training as well? While it may help you up your workouts, a study by Consolazio et al. (1964) found no measurable beneficial effects on muscle strength. This disappointing result was later confirmed by De Haan, et al. (1985). So, I'd venture the guess that - if KMgA is a thing at all - it's an endurance athletes' thing.To test each subject against itself while still having averages to compare, the authors had all subjects perform the "W170", a bicycle ergometer ride at a pulse rate of 170 beats/min (duration ~90 minutes until physical exhaustion) on days 1, 2, 3 and four. And here's how the supplementation worked:
"Beginning at 6 p.m. on the day before day 1, 5 tablets were administered every sixth hrs. last 5 tablets were given 1 hr before the prolonged exercise test on day 4, see Fig. 1. All subjects were given placebo tablets before the tests on days 1, 2 and 4. Before day 3 active substance was given. The subjects were told that the tests were aimed at elucidating the influence of a vitamin tablet on maximal performance time. No information was given to the test supervisor (the same nurse on all days) or to the subjects as to when placebo or active substance was administered. The placebo and active tablets were identically looking" (Ahlborg. 1968)This is admittedly not exactly standard procedure, and one could argue that what we are seeing here is a vitamin placebo effect, but the effect (a) appears to be a bit too large (see data in Figure 1) and you could (b) also argue that the previous two 170Ws may have had a negative effect on the subjects' performance during cycling to exhaustion.
|Figure 1: Duration of prolonged exercise (y-axis) in the 6 test subjects after administration (x-axis) of placebo (striped area) and after administration of aspartate (black area) and individual data in the table (Ahlborg. 1968).|
- Ahlborg, Björn. Capacity for exercise in man. Forsvarets sjukvardsstyrelse, 1967.
- Ahlborg, Bjorn, et al. "Human muscle glycogen content and capacity for prolonged exercise after different diets." Forsvarsmedicin 3.Suppl 1 (1967): 85ą89.
- Ahlborg, Björn, et al. "Muscle glycogen and muscle electrolytes during prolonged physical exercise1." Acta Physiologica Scandinavica 70.2 (1967): 129-142.
- Ahlborg, Björn, Lars‐Göran Ekelund, and Carl‐Gustaf Nilsson. "Effect of Potassium‐Magnesium‐Aspartate on the Capacity for Prolonged Exercise in Man." Acta Physiologica Scandinavica 74.1‐2 (1968): 238-245.
- Consolazio, C. Frank, et al. "Effects of aspartic acid salts (Mg and K) on physical performance of men." Journal of applied physiology 19.2 (1964): 257-261.
- Ekelund, Lars-Göran. "Circulatory and respiratory adaptation during prolonged exercise." Acta physiologica Scandinavica. Supplementum 292 (1967): 1.
- De Haan, A., J. E. Van Doorn, and H. G. Westra. "Effects of potassium+ magnesium aspartate on muscle metabolism and force development during short intensive static exercise." International journal of sports medicine 6.01 (1985): 44-49.
- Hagan, R. D., et al. "Absence of effect of potassium-magnesium aspartate on physiologic responses to prolonged work in aerobically trained men." International journal of sports medicine 3.03 (1982): 177-181.
- Maughan, R. J., and D. J. M. Sadler. "The effects of oral administration of salts of aspartic acid on the metabolic response to prolonged exhausting exercise in man." International journal of sports medicine 4.02 (1983): 119-123.
- Trudeau, François, and René Murphy. "Effects of potassium-aspartate salt administration on glycogen use in the rat during a swimming stress." Physiology & behavior 54.1 (1993): 7-12.
- Wesson, Matthew, et al. "Effects of oral administration of aspartic acid salts on the endurance capacity of trained athletes." Research Quarterly for Exercise and Sport 59.3 (1988): 234-239.