Single- vs. Multi-Joint, Rookie vs. Gymrat - How Much Rest is Required in Trained Athletes if Noobs Need 72h or More?

If you train twice a day, that's certainly too little time for your strength to recover from workout A to workout B. So, if you feel that you must do this (for whatever reason that eludes me) try to put the strength training (like 5x5) first and the strength-endurance workouts (like 3x12-15) later, to make sure you have enough power when you're the most (prolly not fully) recovered.

One reason that it is difficult to impossible to determine the optimal rest time is the fact that we don't have an objective parameter to assess whether it's time to get back to the grind or time to rest. One of the potential and probably useful markers to determine if you're fully (or sufficiently) recovered is the acute decrease in muscle strength in response to intense resistance training that may persist for several hours or days following the training session (Flores. 2011, Nosaka. 2002 & 2005).

Previous studies have linked the early decrease in muscle strength after ST to neural fatigue and muscle acidosis (Byrne. 2004, Crewther. 2006; Sahlin. 1998). The long-lasting reduction of muscle strength for several hours or days or days after your workouts, however, is primarily associated with muscle damage (Nosoka. 2002 & 2005, Roth. 1999).
In rookies, Flores et al. (2011) have been able to show that even 10 sets of curls can decrease the elbow flexor (=biceps) strength below baseline levels for more than 95 hours, i.e. four full days!

Figure 1: While the peak torque recovered only slowly in the 2011 study by Flores, the deep-onset-muscle-soreness (DOMS) returned to (almost) baseline on day four after 10 sets of biceps curls (Flores. 2011).

If you've been training for years, like me, you will probably agree that the results Flores et al. (2011) or Radaelli et al. (2012) observed in untrained people can hardly be relevant for well-trained subjects. Well, I guess Saores et al. probably felt similarly when they set out to compare the time course of muscle strength and DOMS recovery after multi- and single-joint exercises of the elbow flexors in highly resistance trained men.

To investigate the time course of muscle recovery after single- and multi-joint strength exercises, sixteen highly resistance trained men performed two exercise protocols in the same day using a contra-lateral counterbalanced design:

• 8 sets of 10 repetitionmaximum (RM) of unilateral seated row, and 
• 8 sets of 10 RM unilateral bicep curls using  the contralateral arm. 

Participants attended the laboratory on several different occasions. On the first visit, the experimental procedures were explained. On the second visit, the 10 RM loads were assessed. On the third visit, after 72 hours, the 10 RM re-test was performed and subjects were familiarized with the peak torque, and DOMS procedures.
In subsequent visits, subjects performed the exercise protocols, while maximal peak torque and DOMS were measures before, 10 minutes, 24, 48, 72 and 96 hours post exercise. To avoid circadian
influences, subjects were asked to visit the laboratory always at the same time of day. To reduce confounding factors, the volunteers were not allowed to perform any vigorous physical activities or unaccustomed exercise during the experiment period. They were also instructed not to intake medications or supplements during the study period.

Figure 2: Due to being more targeted, the single-joint exercise lead to a higher acute decrease in peak torque. The overall torque recovery, however, was equally fast in both groups (Soares. 2015).

As the data in Figure 2 goes to show you, our gut feeling was right. The highly trained subjects in the study at hand bounced back to their normal performance within one day ... well, at least on the multi-joint exercise, the unilateral row, where the back and the biceps work in concert.

Interestingly enough, the "classic" arms-day (simulation) which is often considered to be a perfect interlude between "heavy days" a "bro" can use to recover lead to significant decreases in peak torque that lasted for more than 24h(!) and were in line with a significantly more pronounced increase in DOMS that declined to normal within 96h only regardless of whether the subjects performed the multi- or single-joint exercise.
References:

• Byrne, Christopher, Craig Twist, and Roger Eston. "Neuromuscular function after exercise-induced muscle damage." Sports medicine 34.1 (2004): 49-69.
• Crewther, Blair, et al. "Possible stimuli for strength and power adaptation." Sports medicine 36.3 (2006): 215-238.
• Flores, Débora F., et al. "Dissociated time course of recovery between genders after resistance exercise." The Journal of Strength & Conditioning Research 25.11 (2011): 3039-3044.
• Nosaka, Kazunori, and Mike Newton. "Difference in the magnitude of muscle damage between maximal and submaximal eccentric loading." The Journal of Strength & Conditioning Research 16.2 (2002): 202-208.
• Nosaka, Kazunori, et al. "Partial protection against muscle damage by eccentric actions at short muscle lengths." Medicine and science in sports and exercise 37.5 (2005): 746-753.
• Radaelli, Regis, et al. "Time course of strength and echo intensity recovery after resistance exercise in women." The Journal of Strength & Conditioning Research 26.9 (2012): 2577-2584.
• Roth, Stephen M., et al. "Ultrastructural muscle damage in young vs. older men after high-volume, heavy-resistance strength training." Journal of Applied Physiology 86.6 (1999): 1833-1840.
• Sahlin, Kent, Michail Tonkonogi, and Karin Söderlund. "Energy supply and muscle fatigue in humans." Acta physiologica Scandinavica 162.3 (1998): 261-266.
• Soares, Saulo, et al. "Dissociated Time Course Of Muscle Damage Recovery Between Single And Multi-Joint Exercises In Highly Resistance Trained Men." Journal of strength and conditioning research/National Strength & Conditioning Association (2015).
• Yeo, Wee Kian, et al. "Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens." Journal of Applied Physiology 105.5 (2008): 1462-1470.