The research done to date on the effects of weight training on cyclists has brought mixed results. The study done by Ben Hurley at the University of Maryland had 10 healthy men take up strength training (bench presses, hip flexions, knee extensions, knee flexions, press-ups, leg presses, lat pulldowns, arm curls, parallel squats, and bent-knee sit-ups) for 12 weeks, while eight other healthy men served as controls. After 12 weeks, the strength-trained men improved their endurance while cycling at an intensity of 75 per cent V02max by 33 per cent and also lifted lactate threshold (the single best predictor of endurance performance) by 12 per cent.
However, these men were untrained prior to the study and did not carry out regular cycling workouts during the research, so the applicability of these findings to serious athletes is questionable
The study carried out by R. C. Hickson and his colleagues at the University of Illinois at Chicago was considerably more practical. In that investigation, eight experienced cyclists added three days per week of strength training to their regular endurance routines over a 10-week period. The strength training was incredibly simple, focusing on parallel squats (five sets of five reps per workout), knee extensions (three sets of five reps), knee flexions (3 x 5), and toe raises (3 x 25), all with fairly heavy resistance. The only progression utilized in the program involved the amount of resistance, which increased steadily as strength improved.
Nonetheless, the strength training had a profoundly positive impact on cycling performance. After 10 weeks, the cyclists improved their 'short-term endurance' (their ability to continue working at a very high intensity) by about 11 per cent, and they also expanded the amount of time they could pedal at an intensity of 80% V02max from 71 to 85 minutes, about a 20-per cent upgrade.
On the negative side, we have research, carried out by James Home and his colleagues at the University of Cape Town in South Africa, seven endurance cyclists who averaged about 200 kilometers of cycling per week incorporated three strength training sessions into their normal routine. The strength program was relatively unsophisticated, consisting of three sets of up to eight repetitions of hamstring curls, leg presses, and quadriceps extensions using fairly heavy resistance.
After six weeks, the strength training had produced rather impressive gains in strength (the gains averaged a bit more than 20 per cent). However, actual cycling performances were not improved; in fact, they were worse than before the strength training was undertaken! 40-K race times slowed from 59 to 62 minutes, and the strength-trained cyclists complained of feeling 'heavy' and tired during their workouts.
Why did Hickson's study uncover clear advantages associated with strength training for cyclists, while Home's work revealed the reverse?
No one knows for certain, which means it's time for a personal observation. It seems quite likely that the strength training carried out by Hickson's charges improved fatigue resistance in their muscles, permitting them to persist longer both during high-intensity tests of endurance and prolonged efforts at a submaximal (80% V02max) intensity. Meanwhile, it's likely that Home's added strength training sent his athletes into the overtrained - or at least 'stale' - state. The feelings of fatigue which originated shortly after the beginning of strength training suggests that the athletes were simply doing too much work.
Home's cyclists were averaging 124 miles of weekly riding when they started their strength training, while Hickson's athletes were logging considerably fewer miles, so one might be tempted to suggest that strength training can produce major benefits for low-mileage cyclists but does much less for experienced, higher mileage competitors who have already built up considerable strength merely by riding. That certainly wouldn't be an unreasonable thought, but it doesn't explain why strength training per se would actually slow down endurance performances, as it seemed to do for Home's performers (no other study has shown this). It seems very likely that Home's added strength training was simply the straw that broke the camel's back; it wasn't the strength training which slowed the cyclists but the total amount of work they had to complete.
Another issue that was not kept controlled in the studies was nutrition and supplementation which also would have a major impact. It is my personal feeling after three decades in the physical training world that weight training is advantageous in almost all sports when done properly and paired with the correct nutrition.