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In one of the first studies to address protein needs of weightlifters, Celejowa and Homa (1970) demonstrated a negative nitrogen balance in at least four out of ten weight lifters who consumed protein in the amount of 2 g/kg/day. Another study on weight lifters suggested a protein intake of 1.3 to 1.6 g/kg/day is sufficient to create a positive nitrogen balance (Laritcheva, Yalovaya, Shubin, and Smirnov 1978). Consolazio and colleagues observed greater nitrogen retention (32.4 vs 7.1 g) in resistance-trained athletes over a forty day training regimen when protein intake was 2.8 g/kg/day versus 1.4 g/kg/day (Consolazio, Johnson, Nelson, Dramise, and Skala 1975). Tarnopolsky published an abstract reporting that a high protein diet of 1.05 g/kg/day resulted in a slightly positive nitrogen balance in body builders, while an even higher protein diet of 2.77 g/kg/day resulted in a more positive nitrogen balance (.62 g/day vs 10.9 g/day) (Tarnopolsky, MacDougall, Atkinson, Blimkie, and Sale 1986). Also supportive of these findings is a study which followed for four weeks two groups of novice weight lifters (Fern, Bielinski, and Schutz 1991). One group consumed their normal protein dietary intake of 1.3 g/kg/day while the higher protein group consumed this amount plus a protein powder supplement of 2g protein/kg/day, giving a total of 3.3 g/kg/day. Nitrogen balance was determined to be .01g N/day and 3.4g N/day, respectively. Similarly, the recent study by Lemon, Tarnopolsky, et al. found enhanced nitrogen retention at 2.62 g/kg/day as opposed to 1.35 g/kg/day (8.9 ± 4.2 and 3.4 ± 1.9g N/day, respectively). Likewise, it has been shown in heavily training body builders consuming a hypoenergetic diet that negative nitrogen balance occurred at 0.8 g/kg/day, but a positive balance was achieved at 1.6 g/kg/day (Walberg, Leedy, Sturgill, Hinkle, Ritchey, and Sebolt 1988). Under milder training conditions in older adults, it was demonstrated that a negative nitrogen balance was achieved at 0.8 g/kg/day, whereas a positive nitrogen balance resulted at 1.62 g/kg/day (Campbell, Crim, Young, Joseph, and Evans 1995).
Interestingly, Oddoye and Margen (1979) illustrated that it is possible to maintain a highly positive nitrogen balance for up to fifty days in the complete absence of resistance exercise. These researchers administered protein in the amount of 3.0 g/kg/day to three subjects, and monitored nitrogen balance for one hundred days total. Although nitrogen retention peaked at fifty days, the nitrogen balance remained positive throughout the remainder of the experiment. This phenomenon is particularly intriguing because prior to this study it was always assumed that excess dietary nitrogen would simply be excreted (Lemon 1991).
Also of interest is the Fern study, which was the first study to show a ceiling for protein intake of resistance-trained athletes by employing labeled metabolic tracers (Fern et al.). The high-protein group, consuming 3.3 g/kg/day, displayed a 150 percent increase in amino acid oxidation, which suggests that the optimal protein intake had been exceeded. Lemon later determined an overload at 2.4 g/kg/day (Lemon, Tarnopolsky, et al.).
What is the effect of a high-protein diet and resistance training on lean body mass?
Using 40K measures (an alternative to nitrogen balance assessment), Torun and his co-investigators measured a decreased cell mass during six weeks of strength training when protein consumption was equal to the RDA. In this study, it is noteworthy that two of the five subjects continued to train for an additional six weeks while consuming an increased protein intake equal to 1.6 g/kg/day, which is twice the RDA. At this increased protein intake, the cell mass of these subjects increased (Torun, Scrimshaw, and Young 1977). Surprisingly, this metabolic demand for protein was caused by isometric exercise or static contractions, which do not damage muscle tissue as severely as the negative or lowering component of isotonic or dynamic contractions. In the Consolazio study previously described, the higher protein group (2.8 g/kg/day) experienced nearly three times the increase in lean body mass as compared to the lower protein group (1.4 g/kg/day). In this study, changes in lean body mass were measured by densitometry (3.28 vs 1.21 kg). Dragan, Vasiliu, and Georgescu (1985) observed a 6 percent increase in lean body mass over several months, as assessed by skin fold measures, among Romanian weight lifters when protein consumption was increased from 2.2 to 3.5 g/kg/day. Utilizing computerized axial tomography (CAT scan), Frontera et al. reported enhanced hypertrophy in the quadriceps of participants in a twelve week study who consumed a daily protein supplement of .33g protein/kg body weight/day in addition to the RDA amount of protein. Urinary creatinine, an index of whole body muscle mass, further substantiated this increase in muscle mass. In a study consisting of two exercise bouts, Morin and Clarkson (1990) failed to find a difference in the circumference of eccentrically trained forearm muscles of females receiving a daily protein supplement containing 37.5 g of high quality protein. A study found leg hypertrophy to be similar between two groups of previously untrained males consuming protein at either 1.30 g/kg/day or 2.94 g/kg/day over the course of thirteen weeks of resistance training (Weideman, Flynn, Pizza, Coombs, Boone, Kubitz, and Simpson 1990). In agreement is the Lemon study (Lemon, Tarnopolsky, et al.) which found similar increases in muscle mass between groups consuming 1.35 g/kg/day and 2.62 g/kg/day. This study is very convincing because changes in muscle mass were assessed via three means: densitometry, creatinine excretion, and CAT scan. In sharp contrast, however, is the Fern research which reported an average of 1.5 kg in the moderate protein group (1.3 g/kg/day) and 2.8 kg in the high protein group (3.3 g/kg/day). Lean body mass was estimated through skin fold measurement and underwater weighing (Fern et al.). Most recently, a group of Brazilian researchers showed an impressive 3.28 kg muscle increase in one month using body builders consuming an average of 2.0 g/kg/day (Maestá, Cyrino, Corrêa, Bicudo, Angeleli, Tsuji, and Burini 1998).
Interestingly, Oddoye and Margen (1979) illustrated that it is possible to maintain a highly positive nitrogen balance for up to fifty days in the complete absence of resistance exercise. These researchers administered protein in the amount of 3.0 g/kg/day to three subjects, and monitored nitrogen balance for one hundred days total. Although nitrogen retention peaked at fifty days, the nitrogen balance remained positive throughout the remainder of the experiment. This phenomenon is particularly intriguing because prior to this study it was always assumed that excess dietary nitrogen would simply be excreted (Lemon 1991).
Also of interest is the Fern study, which was the first study to show a ceiling for protein intake of resistance-trained athletes by employing labeled metabolic tracers (Fern et al.). The high-protein group, consuming 3.3 g/kg/day, displayed a 150 percent increase in amino acid oxidation, which suggests that the optimal protein intake had been exceeded. Lemon later determined an overload at 2.4 g/kg/day (Lemon, Tarnopolsky, et al.).
What is the effect of a high-protein diet and resistance training on lean body mass?
Using 40K measures (an alternative to nitrogen balance assessment), Torun and his co-investigators measured a decreased cell mass during six weeks of strength training when protein consumption was equal to the RDA. In this study, it is noteworthy that two of the five subjects continued to train for an additional six weeks while consuming an increased protein intake equal to 1.6 g/kg/day, which is twice the RDA. At this increased protein intake, the cell mass of these subjects increased (Torun, Scrimshaw, and Young 1977). Surprisingly, this metabolic demand for protein was caused by isometric exercise or static contractions, which do not damage muscle tissue as severely as the negative or lowering component of isotonic or dynamic contractions. In the Consolazio study previously described, the higher protein group (2.8 g/kg/day) experienced nearly three times the increase in lean body mass as compared to the lower protein group (1.4 g/kg/day). In this study, changes in lean body mass were measured by densitometry (3.28 vs 1.21 kg). Dragan, Vasiliu, and Georgescu (1985) observed a 6 percent increase in lean body mass over several months, as assessed by skin fold measures, among Romanian weight lifters when protein consumption was increased from 2.2 to 3.5 g/kg/day. Utilizing computerized axial tomography (CAT scan), Frontera et al. reported enhanced hypertrophy in the quadriceps of participants in a twelve week study who consumed a daily protein supplement of .33g protein/kg body weight/day in addition to the RDA amount of protein. Urinary creatinine, an index of whole body muscle mass, further substantiated this increase in muscle mass. In a study consisting of two exercise bouts, Morin and Clarkson (1990) failed to find a difference in the circumference of eccentrically trained forearm muscles of females receiving a daily protein supplement containing 37.5 g of high quality protein. A study found leg hypertrophy to be similar between two groups of previously untrained males consuming protein at either 1.30 g/kg/day or 2.94 g/kg/day over the course of thirteen weeks of resistance training (Weideman, Flynn, Pizza, Coombs, Boone, Kubitz, and Simpson 1990). In agreement is the Lemon study (Lemon, Tarnopolsky, et al.) which found similar increases in muscle mass between groups consuming 1.35 g/kg/day and 2.62 g/kg/day. This study is very convincing because changes in muscle mass were assessed via three means: densitometry, creatinine excretion, and CAT scan. In sharp contrast, however, is the Fern research which reported an average of 1.5 kg in the moderate protein group (1.3 g/kg/day) and 2.8 kg in the high protein group (3.3 g/kg/day). Lean body mass was estimated through skin fold measurement and underwater weighing (Fern et al.). Most recently, a group of Brazilian researchers showed an impressive 3.28 kg muscle increase in one month using body builders consuming an average of 2.0 g/kg/day (Maestá, Cyrino, Corrêa, Bicudo, Angeleli, Tsuji, and Burini 1998).
