The purpose of this study was to determine whether resistance training through a full range of motion could be as effective or more effective than static stretching of the same joints.  Twenty five volunteers were randomly placed in two groups: resistance training (RT) and static stretching (SS).  The subjects hamstring extension, hip flexion, shoulder extension flexibility, and peal torque of quadriceps and hamstrings were pretested prior to completing a 5 week static stretching or resistance training intervention.  
The results concluded that there was no difference between the two groups suggesting that resistance training through a full range of motion is potentially as effective as static stretching.  
This study speaks to how important strength training through a full range of motion is.  Often athletes perform weight training with half or three quarters full range of motion.  However, as this small study begins to point out, if we can get our athletes to perform full range of motion on all strength training exercises, we can get them more flexible while improving their strength.  Larger studies with longer durations will need to be studied to support or disprove these results.  

Concurrent Training is a type of training that is often implemented into strength and conditioning programs for team sports, as well as individual sports.  However, we must consider the primary physiological demands of the sport.  Does it require power? Endurance? Strength? Or a combo?  What energy systems are used the most?  All of these questions should be answered when thinking about concurrent training.  
Patrick Ward is a massage therapist, certified strength and conditioning specialist, certified personal trainer, and USA weightlifting certified coach.   He holds many other certifications in active release technique, functional movement screen, and titlelist performance institute.  He is well respected in the fitness industry and owns a sports performance center in Arizona.  This article speaks to some of the important points of concurrent training.  He reports the summary of a research article about this topic in the Journal of Strength & Conditioning Research:  
  

1. Hypertrophy and max strength did not differ between the strength only and the concurrent training groups, however, power was significantly decreased in the concurrent training group versus the strength training only group.
2. No decrements were found in VO2max between an endurance only group or a concurrent training group which indicates that aerobic capacity may not really be inhibited by this method of programming. An interesting aside is the same result has also been seen in elite endurance athletes.
3. Concurrently performing strength training and running led to significant decrements in hypertrophy and strength gains however this result was not found to be the case when strength training was performed concurrently with cycling. The authors hypothesized that his may be due to the fact that cycling is more biomechanically similar to many of the strength tests used in the study or since running has a higher eccentric component (while cycling is primarily concentric) there may be potential for greater muscle damage. However, despite the performance decrements, concurrent training with running led to a greater decline in fat mass versus concurrent training with cycling.
4. While the common ground between long duration endurance training and resistance training is low (as I indicated above when discussing the interference phenomenon) there does appear to be a common ground between short duration, high-intensity, sprinting and resistance exercise due to the way the neuromuscular system is recruited for these tasks.

Additionally, he adds some of his personal thoughts based on his experience.  His article on this topic is very well thought out and researched, as are many of his blog posts.  I encourage you to read though some of his blog in your spare time as he presents a lot of very good topics.

What age is trainable for implementing plyometrics?  This study sought to find out whether preadolescent soccer players would benefit from combined soccer specific training and plyometric training 2x/week.  
The study design was a randomized control trial with 45 participants over a 12 week span.  The authors assigned a control group that participated in only soccer practice, while the plyometric group trained twice a week with 72hrs in between sessions. 
Speed (0–10, 10– 20, 20–30 m), leg muscle power (static jumping, countermove- ment jumping, depth jumping [DJ], standing long jump [SLJ], multiple 5-bound hopping [MB5]), leg strength (10 repetition maximum), anaerobic power (Wingate testing), and soccer- specific performance (agility, kicking distance) were measured at baseline, midtraining, and post-training.  The authors found that the plyometric group had a improvement in all speed tests (1.9-3.1% at midtraining, 3.5% at posttraining) and vertical jump tests (10.5-18.5% at midtraining and 16-23% at posttraining).  Additionally, standing long jump, multiple bounding, leg strength, agility, and kicking distance were significantly increased at mid and posttraining.  
In conclusion, what we can take away from this study is that plyometric training in combination with sport-specific training can be very effective in preadolecent athletes.  It has been debated before whether chronological age and training age plays a role in plyometric benefits and although this is only one study, it gives us some indication that plyometrics can be effective in younger populations.